Producing Larkspur As Cut Flowers Inc

References Reviewed by Armitage, Allan M. 1993. “Specialty Dr. John Dole, Oklahoma State Cut Flowers.” Athens, GA: Varsity Press, University Producing Larkspur as Cut Flowers Inc. Dr. Will Healy, George Ball Seed Gill, Stanton A. and J. Sanderson. 1997. Company, Inc. “Ball Greenhouse Pest Identification and Fact Sheet 713 IPM Control.” (In press.) Illustrations by Nau, Jim. 1995. “Ball Perennial Raymond Bosmans, Regional Specialist, Manual: Propagation and Production.” CES Home and Garden Information Batavia, Illinois: Ball Publishing. Center Powell, Charles and Richard Linguist. 1992. “Ball Pest and Disease Manual: Disease, Insect, and Mite Control on Flower and Foliage Crops.” Batavia, Illinois: Ball Publishing. Note: When trade names are included, no dis- Woods, Christopher. 1992. crimination against similar products is intended. “Encyclopedia of Perennials.” New York Mention of trademarks in this publication does not constitute an endorsement by the Cooperative City: Facts on File, Inc. Stanton Gill Introduction Extension Service. regional Extension specialist Central Maryland Research and Education Center Larkspur, Consolida spp., are excellent cut flowers—both for fresh and dried or Ethel Dutky plant pathologist everlasting markets. Many cut flowers are Department of Entomology popular for short periods of time, often University of Maryland at College Park attracting public attention for less than 5 years, then fading from demand. The Russell Balge market for good quality larkspur has been regional Extension specialist strong for many years, past the period of Western Maryland Research and Education Center “fad flowers,” and it continues to stay Tom Blessington robust. The alluring flower shape, wide regional Extension specialist range of colors, and appealing foliage all Central Maryland Research and Education Center combine to make larkspur a popular, mar- ketable cut flower. The flowers tend to be David Ross somewhat fragile and relatively short- Extension agricultural engineer lived in the vase (under 7 days), making Department of Biological Resources Engineering production for local markets very appeal- University of Maryland at College Park ing. Bryan Butler faculty Extension assistant Larkspur grow to their full potential in Carroll County climates with cool, moist summers. Growers must adopt practices that take Ginny Rosenkranz advantage of the cooler seasons to suc- faculty Extension assistant cessfully grow larkspur as a cut flower Wicomico and Worchester Counties crop in Maryland. Maryland growers Suzanne Klick often establish sequence plantings of commercial horticulture technician larkspur during the cool weather of Central Maryland Research and Education Center September through heavy frost. Plants P97 Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30,1914, in cooperation with the U.S. Department of Agriculture, University of Maryland at College Park, and local governments. Thomas A. Fretz, Director of Cooperative Extension Service, University of Maryland at College Park. The University of Maryland is equal opportunity. The University’s policies, programs, and activities are in conformance with pertinent Federal and State laws and regulations on nondiscrimination regarding race, color, religion, age, national origin, sex, and disability. Inquiries regarding compliance with Title VI of the Civil Rights Act of 1964, as amended; Title 12 IX of the Educational Amendments; Section 504 of the Rehabilitation Act of 1973; and the Americans With Disabilities Act of 1990; or related legal requirements should be directed to the Director of Personnel/Human Relations, Office of the Dean, College of Agriculture and Natural Resources, Symons Hall, College Park, MD 20742. established in the fall grow rapidly in Larkspur seed does not germinate well Consumer Care cool, moist springs, with heavy flower when soil temperatures are held above production in May and June and occa- 75 °F. Germination will be improved by • Recut stems under water and place sionally into July if the weather remains chilling seed (35 to 40 °F) for at least 7 to flowers in clean warm water contain- favorable. 14 days prior to planting. In Maryland, ing a floral preservative. optimum seeding times for field produc- • Avoid temperature extremes such as The genus of larkspur was recently tion are from September through heavy freezing or temperatures over 95 °F. changed from Delphinium to Consolida. frost. Most growers will plant a series of • Keep flowers away from rapid air Two species of larkspur are used for cut sequence plantings at 2-week intervals. movement. flowers: Consolida ambigua and Consolida Germination takes place 12 to 20 days orientalis. C. orientalis is more upright • Avoid keeping flowers near ripening after sowing. Once the seed has germinat- fruit, which emits ethylene. than C. ambigua, and colors are often ed, the larkspur plants will grow rapidly shades of bright pink and purple. C. in cool fall weather. Larkspur plants plant- ambigua have more branches initially and ed in fall flower 4 to 6 months after plant- colors are usually light pink or blue. Most ing. of the outstanding larkspurs for cut flower production are C. orientalis vari- eties.

Culture

Field Production

Propagation Larkspur is commonly produced by direct seeding into the field. Some growers start or purchase seedlings grown in greenhouse Summary plug trays, and transplant lark- • Select larkspur cultivars and site. spur plugs into the field or greenhouse growing beds. • For field production, prepare seed beds in the fall and plant a Larkspur has a reputation series of sequence plantings at 2- for poor germination. Seeds week intervals. that germinate best are • Grow plants in full sun, prefer- An alterna- ably in raised beds those planted 4 to 6 tive is to start months after harvest. with trickle irriga- seeds in a green- tion. Seed 1 year or older often house during the • Monitor for aphids has germination rates of winter and trans- less than 50 percent. and cyclamen plant the plugs in mites. Stored seed should be early spring. For refrigerated until need- • Monitor for dis- greenhouse growing, use eased plants and ed, but held for under 1 a germination temperature of promptly remove year. An ounce of seed 70 °F, with a light covering of coarse those that are yields approximately 5,000 vermiculite. Transplants from the green- infected. plants. house should be conditioned at tempera-

2 11 • Pretreatment. Pulse with silver thio- tures below 55 °F for 4 to 6 weeks before devices that monitor soil moisture and sulfate (STS) to minimize ethylene being moved into the field in April. can be used to help the grower decide damage and prolong vase life. Use a Yields of cut flowers seed-started in green- when to irrigate. (For more information, commercial silver solution according houses are generally not as heavy as refer to University of Maryland Extension to label directions, preferably for a 1- yields from plants field-started in the fall. to 2-hour treatment. The STS solu- Service Bulletin 312, ”Soil Moisture tion must be processed for silver Sensors for Irrigation Management.”) recovery before it can be disposed of Site selection down a drain. Commercial devices, Select a location that receives at least 8 Nutrition such as a Superbatcher, are specially hours of direct sunlight. A source of designed to remove the silver from Adding a 1- to 2-inch layer of compost- STS. water near the site is good because an irrigation system is frequently needed for ed organic material and tilling it in will STS is not very stable, giving the greatly benefit larkspur growth. Larkspur solution a relatively short shelf life. best quality production. Larkspur grows Unfortunately, it is not always easy best in well-drained soil with a pH of 6.0 plants also respond favorably to applica- to determine whether your STS solu- to 7.0. Using a raised bed improves tions of nitrogen fertilizer. If using trickle tion is still active. Test kits are avail- drainage and will also warm the bed earli- irrigation, fertilize on a weekly basis with able to test the solution’s effective- er in the spring. Wide spacing of 10 to 12 100 parts per million (ppm) of complete ness. inches between plants will provide more fertilizer based on nitrogen. Water-driven • Hydration. Hydrate in clean, warm cut flower stems per plant. The yield per fertilizer injectors are available that add water (80 to 90 °F) at pH 3.5 to 4.0. square foot will increase with a closer the correct proportion of concentrated • Preservation. Use a floral preserva- spacing of 4 to 5 inches between plants, soluble into the irrigation water. If pro- tive for maximum longevity. but will decrease per individual plant. ducing larkspur without trickle irrigation, • Temperature. Refrigerate at 35 to side dress with a complete fertilizer (10-5- 40 °F. Support 10 or 10-6-4 ratio) at 1 pound per 100 Most larkspur cultivars grow to a square feet of production row. height of 3 to 4 feet. Unsupported flowers will often fall over with the stems turning upward. To maintain the quality of cut Greenhouse Production flowers, one or two layers of net or wire Larkspur is best grown in groundbeds support (6- to 8-inch openings) are rec- to facilitate production and harvesting. ommended to help hold flowers upright. The seeds should be sown from Irrigation September through November. Maintain temperatures at 50 to 55 °F for 8 to 10 Installing a trickle irrigation system is a weeks. Raise temperatures to 55 to 60 °F worthwhile investment. Irrigation is best after this time. Larkspur needs day achieved using irrigation rowcrop tape or lengths of 16 hours to flower. The day rowcrop emitter tubing that lies down length can be extended with lighting or the row with emitters spaced 6 to 12 inches apart. Two or three rowcrop tapes with 2-hour night break lighting using on a raised bed will water several rows of incandescent lamps. plants across the bed. Coarse soils need more tapes. Water frequently enough to Nutrition maintain a good soil moisture. Use a screen filter of 100 to 140 mesh to pre- Greenhouse-grown larkspur needs vent clogging and use a small pressure weekly applications of a dilute soluble regulating device set at 8 to 10 psi to complete fertilizer (for example, 20-10-20 ensure the proper operating pressure for or 15-5-15 ratio) at 100-200 ppm based the trickle tubing. Tensiometers are on nitrogen.

10 3 Cultivars blooms have fully opened. If shipping the the flowers by hanging flower stems flowers, try to harvest before the lower upside down and drying at 70 to 80 °F for •Consolida orientalis: one-third of the flower stem has opened. 10 to 14 days. A well-ventilated drying Giant Imperial series—The standard For direct markets, you may choose to barn is ideal for preserving larkspur. of the industry. Plants grow 3 to 4 harvest when one-half to three-quarters feet tall. Colors: carmine, deep blue, of the flower stem has opened. The vase deep rose, light blue, lilac, pink, Postproduction Factors salmon, and white. life of larkspur is between 5 to 7 days. The flower blooms are highly sensitive to Messenger series—Plants are 3 to 4 ethylene and will shatter in its presence. feet tall and flower 2 weeks earlier Retail handling than the Giant Imperial series. To hold larkspur for 1 to 2 days, place stems in fresh water, keeping them • Recut stems. After bringing larkspur Colors: Blue, lilac, rose, and white. in from the field, recut stems under upright and maintaining temperatures of Early Bird series—Earlybird flowers water to prevent a water uptake 2 to 3 weeks earlier than Giant 34 to 40 °F. blockage. Imperial. Plants are 3 to 4 feet tall. • Ethylene. Flowers are highly sensi- Colors: blue, lilac, rose, white, and Everlasting sales tive to ethylene, with resulting pre- mixed. mature dropping of flowers. Flowers Larkspur are relatively easy to dry for QIS series—Very uniform plants and will react when exposed to ethylene thick stems. Plants grow 2 to 3 feet sale as everlasting flowers. For everlasting at 3 ppm for 24 hours at 70 °F. tall. Colors: carmine, dark blue, light flowers, harvest when the majority of the Causes include shipping with mixed- pink, lilac, rose, white, and mixed. flowers have opened, but before the bot- fruit or decaying plant material. tom flower petals have dropped. The feathery foliage does not need to be removed when dry- Pests ing the flower stems. Air dry

Major Diseases The most important diseases of larkspur cut flower production are damping off of seedlings (Pythium and Rhizoctonia fungi), Botrytis, powdery mildew, and Southern blight.

Damping off and seedling root rots Several species of the water mold Pythium attack larkspur seedlings. Both cool and warm temperature species are reported. Wet conditions favor Pythium diseases. Pythium may rot the germinating seed (preemergence damping off), or cause root rot that stunts or kills seedlings (postemergence damping off). Pythium produces a tan, water-soaked appearance in roots and stem. The root cortex may slough off leaving the white root vascular cylinder exposed, like fine white threads.

4 9 Chemical control of cyclamen mites. emergents must be applied after the lark- The fungus Rhizoctonia solani can also aged tissues in a moist chamber overnight Since cyclamen mites are found in cryp- spur seed germinates to prevent inhibit of cause damping off and seedling blight. to promote the formation of spores. tic (small, hidden) locations on the plant, larkspur germination. If plants are estab- Usually Rhizoctonia is favored by warm spray applications must be made as a fine lished in the fall, preemergent herbicides conditions. When compared to Pythium, The Botrytis fungus has developed mist. Use of a spreader sticker to increase can be applied to weed-free soil around Rhizoctonia lesions are more defined, with resistance to several major classes of chance of contact with the pest is recom- growing plants in the spring to control tan, sunken areas. Sometimes the light chemical fungicides, including the benz- mended. Check with your local spring-germinating annual weeds. The tan, fine “cob web” mycelium of imidazoles (e.g., Cleary’s 3336 and Cooperative Extension office for current- preemergent Dacthal prevents germina- Rhizoctonia can be seen on blighted plant Domain) and the dicarboximides (Chipco ly labeled miticides. Usually, the best tion of several annual weed grasses and a parts and growing across the soil surface. 26019), making chemical control diffi- action is to destroy infested plants before few broadleaf annual weeds. The preemer- cult. When extended periods of wet over- the problem spreads in the planting. gent Pennant is effective against annual To differentiate Pythium from cast weather occur, it may be helpful to grasses, yellow nutsedge, and several Rhizoctonia, use an Alert on-site diagnos- spray with mancozeb or use Exotherm broadleaf annual weeds. Check with your tic kit. This will permit you to select the Termil smoke in the greenhouse. The cop- Weed Control local Cooperative Extension Service for correct fungicide for control. per fungicide Phyton 27 is also registered current recommendations on other pre- for Botrytis control on flowers. To maximize both floral quality and emergent herbicides labeled for use in Basic good horticultural practices, sani- quantity, weed control is essential in field-produced cut flowers. tation, and providing optimum condi- both field and inground greenhouse pro- tions for seed germination and seedling Powdery mildew duction of larkspur. Competition for Glyphosphate (sold under several growth can prevent most damping-off Some larkspur cultivars are susceptible nutrients, moisture, and light can be brand names, including Round-up) can losses. Selecting a well draining media to powdery mildew caused by the fungus reduced with a good weed control pro- provide postemergent control of grasses and watering early in the day so soil Erysiphe polygoni. Symptoms include gram. In a greenhouse, soils can be steam and broadleaf weeds. Apply a 33 percent drains well before nightfall helps control twisted and distorted foliage and white sterilized at 160 °F for 30 minutes to kill Glyphosphate solution with a wick appli- Pythium. SoilGard, a biological fungicide, spots and patches on foliage, stems, and most weed seeds. A weed barrier of 2- to cator. Use extreme caution with this solu- can be added to media to provide excel- buds. Flower buds may fail to open and 4-mL black plastic with holes made for tion. Be careful not to make contact with lent control of both Pythium and flowers may be distorted and unsalable. placement of plant plugs or seeds can the larkspur or the Glyphosphate will kill Rhizoctonia. Weather conditions that favor powdery greatly reduce the need for weeding. your desired plants as well as the weeds. mildew are sunny, warm, dry days, and Unfortunately, the black plastic tends to Botrytis blights cool nights. cause the soil temperatures to rise, which Some growers have used methyl bro- will affect the quality of the larkspur mide to fumigate the soil before direct Botrytis can attack seedlings, but it is Several systemic fungicides (e.g., crop. A light layer of leaves or bark can seeding of larkspur. Used for years, this especially damaging when it spots and Funginex, Terraguard, Strike, Banner) and be laid over the black plastic to reduce soil fumigant kills weeds, seeds, and blights flowers. High humidity and a film summer oil sprays all provide good con- the heat buildup. many insect and disease species. It is of water on plant surfaces is necessary for trol of powdery mildew. Some larkspur presently still available for use by certified Botrytis to infect plant tissues. Thus, any cultivars are less susceptible. Keep good Another option for weed control is to pesticide applicators, but is being phased cultural practice that reduces periods of records of disease incidence on each culti- use organic mulch as a surface applica- out of the market because it is extremely leaf wetness (trickle irrigation, plant spac- var you grow; you can then select resis- tion. If seeding is done in the fall, a 1- toxic. Basamid (granular formulation) can ing to improve air circulation, use of hor- tant cultivars. inch organic mulch layer (composted also be used as a soil fumigant and is izontal air flow fans in greenhouses, etc.) leaves or grass clippings) can be applied much safer than methyl bromide. will reduce the risk of Botrytis. Southern blight close to the plants after they germinate. The mulch layer will reduce germination Botrytis produces a small, defined spot The Southern blight fungus Sclerotium of fall-germinating weeds. In the spring, that may rapidly enlarge to blight the rolfsii (also called Sclerotium delphini by if the organic mulch layer has thinned flower, leaf, or stem. Weak plant tissues some authors) can be a serious problem in out, an additional 1-inch layer can be Harvesting Larkspur such as yellowing senescent foliage, field-grown larkspur during hot weather. flower petals, and wounds are easily The fungus remains in the upper inches placed on the soil to reduce germination Fresh market sales of spring-germinating weeds. invaded by Botrytis. Under humid condi- of field soil and is only active during peri- Larkspur flowers start opening from the tions a gray mold is produced on blighted ods of hot weather when soil tempera- A chemical option to prevent annual bottom and progressively open up from tissues. This gray mold is diagnostic of tures rise into the upper 70s. The fungus weeds from germinating would be to the flower stem to the top. For fresh mar- Botrytis. Look for this aerial gray mold attacks the plant at the soil surface, caus- apply a preemergent herbicide. The pre- ket sales, harvest when several lower early in the morning or incubate dam- ing a rapid wilt and crown rot of individ-

8 5 ual scattered plants in the field. Close Major Insects duce in the field. For pupation the larvae Cyclamen mites are minute (less than inspection of wilting plants will find drops to the ground and burrows about 0.2 mm). Often a grower will notice dam- white wefts of mycelium on the stem, Aphids an inch into the soil before spinning a age caused by these mites before actually often webbing soil particles and mulch cocoon. When you order the midge, it is Aphids can rapidly become a major seeing them. A pocket magnifier micro- to the stem. The small (about 1/8 to generally shipped as a red-orange pupae. scope with at least 30 X is needed to see 1/4 inch), spherical, white to brown pest in larkspur plantings if the popula- Place the pupal casing on the soil of the mites. The outer cuticle is hard and sclerotia are formed on stems and soil. tion is left unchecked. Large populations plants that have aphid populations. If Presence of the sclerotia is diagnostic of of aphids will result in noticeable honey- aphid populations are extremely high, shiny and there are relatively few setae Southern blight. dew accumulations on foliage and flow- apply either 2 percent horticultural oil or (hairs) on the body compared to other ers. Sooty mold fungus will grow on the 2 percent insecticidal soap 1 or 2 days plant-damaging mites. Several management practices will honeydew. Since aphids feed on plant before you release the midges. The release reduce Southern blight. Deep tillage buries phloem, they compete with the plant for rate for low aphid populations is 1 midge Female cyclamen mites lay eggs in clus- the sclerotia and will reduce the disease nutrients. Heavy populations may mea- per 10 square feet. For higher infestations ters of two to three eggs, usually between because the sclerotia require warmth and surably reduce plant growth and vigor. of aphids release them at 1 midge per 5 young leaves of the bud or at the crown oxygen to grow. Incorporating organic square feet of growing area. of the plant. Each female lays 10 to 40 matter will help by promoting decay of Before you attempt to control aphids you need to identify the species of aphid. eggs over a 12- to 16-day life cycle. Eggs the sclerotia during the fall, winter, and Chemical control of aphids. are white, ovoid, and smooth. The larva is Samples can be submitted to your local Horticultural oils, insecticidal soaps, and spring. Wilting plants should be promptly white in color, and has six legs with removed along with any mycelium and Cooperative Extension office for identifi- neem are three biorational chemicals that microscopic claws and suction cups. sclerotia to reduce further increase in fun- cation. Next, familiarize yourself with the suppress aphid populations. Biorational gal inoculum in the field. Fungicide con- biology of the aphid in a particular crop. chemicals are materials that have short Adult females are yellowish and have trols and biological agents that decay the Note how fast they reproduce; whether residuals and minimal impact on benefi- eight legs. The males are often colorless to sclerotia are in development and may they have a preference for feeding on cial insects and nontarget organisms. yellowish-brown. Males often pick up and soon be widely registered. only certain parts of the plant, or a prefer- Because these chemicals have no long- transport females transforming into ence for feeding on certain species or cul- term residual effects, regular monitoring of adults or adult females with their semi- tivars of plants. One species of aphid that aphid populations is recommended and erect hind legs. Female cyclamen mites Miscellaneous leaf spots is commonly found on larkspur is the repeated applications of the chemicals can reproduce without mating (partheno- green peach aphid, Myzus persica. This A number of fungi (Cercospora, may be necessary. genetically). Ramularia, Ascochyta, Phyllosticta, aphid species is very difficult to control with chemical applications. Septoria) are reported to cause leaf spots Two systemic insecticides that give The cyclamen mite is very difficult to good control of aphids are acephate on larkspur. Lab examination is needed control since its habitat is in tight, con- to differentiate these minor leaf spot Biological control of aphids. Aphid (Orthene) and midicloprid (Merit). Once fined parts of the plant. Early detection of diseases. All are promoted by extended populations can be controlled by naturally a systemic has dried and been absorbed periods of leaf wetness. Fungicide occurring parasites and predators. If popu- by the plant, the effect on beneficial damage symptoms and subsequent sprays can prevent infections and lations of aphids are detected at the early arthropods is minimal. destruction of infested plants is the best reduce spread if applied promptly stage of development, you have the course of action cut flower growers can option of using beneficial insects to con- when first leaf spots are seen. However, Cyclamen mites take. leaf spots are seldom serious enough to trol aphid populations. Aphidoletes justify a preventive spray schedule. If aphidimyza, a midge insect in the order The cyclamen mite, Phytonemus pallidus, Biological control of cyclamen mites. you experience unusually prolonged Diptera, can be used for controlling aphids can cause injury to larkspur. The feeding Neoseilus (=Amblyseius) cucumeris periods of wet weather, the fungicides that are difficult to control with chemicals damage is exhibited in buds and flowers (Oudemans) is a commercially available Cleary’s 3336, Daconil 2787, Protect such as the green peach aphid. This midge that are distorted and often stunted. Leaf mite that is used mainly to control first lives an average of 10 days and lays eggs TO, and others would be effective in buds of badly infested plants are some- and second instar thrips, but this phyto- close to aphid colonies. The resulting times completely destroyed. Adult and preventing most leaf spots. seid mite also will feed on cyclamen orange midge larvae can kill aphids by bit- larva of cyclamen mite occur in hidden ing them at the knee joint and injecting a areas on the plant. They appear to avoid mites. N. cucumeris has successfully been paralyzing toxin. They grow to maturity direct light and require humidity levels used to control cyclamen mite on straw- over a 3- to 5-day period. They will kill near saturation, which is found between berries, but additional field research needs from 40 to 60 aphids each, depending on tightly packed young leaves, or around to be conducted on use of this predaceous the aphid density. The midge will repro- flower buds. mite in cut flower fields.

6 7 ual scattered plants in the field. Close Major Insects duce in the field. For pupation the larvae Cyclamen mites are minute (less than inspection of wilting plants will find drops to the ground and burrows about 0.2 mm). Often a grower will notice dam- white wefts of mycelium on the stem, Aphids an inch into the soil before spinning a age caused by these mites before actually often webbing soil particles and mulch cocoon. When you order the midge, it is Aphids can rapidly become a major seeing them. A pocket magnifier micro- to the stem. The small (about 1/8 to generally shipped as a red-orange pupae. scope with at least 30 X is needed to see 1/4 inch), spherical, white to brown pest in larkspur plantings if the popula- Place the pupal casing on the soil of the mites. The outer cuticle is hard and sclerotia are formed on stems and soil. tion is left unchecked. Large populations plants that have aphid populations. If Presence of the sclerotia is diagnostic of of aphids will result in noticeable honey- aphid populations are extremely high, shiny and there are relatively few setae Southern blight. dew accumulations on foliage and flow- apply either 2 percent horticultural oil or (hairs) on the body compared to other ers. Sooty mold fungus will grow on the 2 percent insecticidal soap 1 or 2 days plant-damaging mites. Several management practices will honeydew. Since aphids feed on plant before you release the midges. The release reduce Southern blight. Deep tillage buries phloem, they compete with the plant for rate for low aphid populations is 1 midge Female cyclamen mites lay eggs in clus- the sclerotia and will reduce the disease nutrients. Heavy populations may mea- per 10 square feet. For higher infestations ters of two to three eggs, usually between because the sclerotia require warmth and surably reduce plant growth and vigor. of aphids release them at 1 midge per 5 young leaves of the bud or at the crown oxygen to grow. Incorporating organic square feet of growing area. of the plant. Each female lays 10 to 40 matter will help by promoting decay of Before you attempt to control aphids you need to identify the species of aphid. eggs over a 12- to 16-day life cycle. Eggs the sclerotia during the fall, winter, and Chemical control of aphids. are white, ovoid, and smooth. The larva is Samples can be submitted to your local Horticultural oils, insecticidal soaps, and spring. Wilting plants should be promptly white in color, and has six legs with removed along with any mycelium and Cooperative Extension office for identifi- neem are three biorational chemicals that microscopic claws and suction cups. sclerotia to reduce further increase in fun- cation. Next, familiarize yourself with the suppress aphid populations. Biorational gal inoculum in the field. Fungicide con- biology of the aphid in a particular crop. chemicals are materials that have short Adult females are yellowish and have trols and biological agents that decay the Note how fast they reproduce; whether residuals and minimal impact on benefi- eight legs. The males are often colorless to sclerotia are in development and may they have a preference for feeding on cial insects and nontarget organisms. yellowish-brown. Males often pick up and soon be widely registered. only certain parts of the plant, or a prefer- Because these chemicals have no long- transport females transforming into ence for feeding on certain species or cul- term residual effects, regular monitoring of adults or adult females with their semi- tivars of plants. One species of aphid that aphid populations is recommended and erect hind legs. Female cyclamen mites Miscellaneous leaf spots is commonly found on larkspur is the repeated applications of the chemicals can reproduce without mating (partheno- green peach aphid, Myzus persica. This A number of fungi (Cercospora, may be necessary. genetically). Ramularia, Ascochyta, Phyllosticta, aphid species is very difficult to control with chemical applications. Septoria) are reported to cause leaf spots Two systemic insecticides that give The cyclamen mite is very difficult to good control of aphids are acephate on larkspur. Lab examination is needed control since its habitat is in tight, con- to differentiate these minor leaf spot Biological control of aphids. Aphid (Orthene) and midicloprid (Merit). Once fined parts of the plant. Early detection of diseases. All are promoted by extended populations can be controlled by naturally a systemic has dried and been absorbed periods of leaf wetness. Fungicide occurring parasites and predators. If popu- by the plant, the effect on beneficial damage symptoms and subsequent sprays can prevent infections and lations of aphids are detected at the early arthropods is minimal. destruction of infested plants is the best reduce spread if applied promptly stage of development, you have the course of action cut flower growers can option of using beneficial insects to con- when first leaf spots are seen. However, Cyclamen mites take. leaf spots are seldom serious enough to trol aphid populations. Aphidoletes justify a preventive spray schedule. If aphidimyza, a midge insect in the order The cyclamen mite, Phytonemus pallidus, Biological control of cyclamen mites. you experience unusually prolonged Diptera, can be used for controlling aphids can cause injury to larkspur. The feeding Neoseilus (=Amblyseius) cucumeris periods of wet weather, the fungicides that are difficult to control with chemicals damage is exhibited in buds and flowers (Oudemans) is a commercially available Cleary’s 3336, Daconil 2787, Protect such as the green peach aphid. This midge that are distorted and often stunted. Leaf mite that is used mainly to control first lives an average of 10 days and lays eggs TO, and others would be effective in buds of badly infested plants are some- and second instar thrips, but this phyto- close to aphid colonies. The resulting times completely destroyed. Adult and preventing most leaf spots. seid mite also will feed on cyclamen orange midge larvae can kill aphids by bit- larva of cyclamen mite occur in hidden ing them at the knee joint and injecting a areas on the plant. They appear to avoid mites. N. cucumeris has successfully been paralyzing toxin. They grow to maturity direct light and require humidity levels used to control cyclamen mite on straw- over a 3- to 5-day period. They will kill near saturation, which is found between berries, but additional field research needs from 40 to 60 aphids each, depending on tightly packed young leaves, or around to be conducted on use of this predaceous the aphid density. The midge will repro- flower buds. mite in cut flower fields.

6 7 Chemical control of cyclamen mites. emergents must be applied after the lark- The fungus Rhizoctonia solani can also aged tissues in a moist chamber overnight Since cyclamen mites are found in cryp- spur seed germinates to prevent inhibit of cause damping off and seedling blight. to promote the formation of spores. tic (small, hidden) locations on the plant, larkspur germination. If plants are estab- Usually Rhizoctonia is favored by warm spray applications must be made as a fine lished in the fall, preemergent herbicides conditions. When compared to Pythium, The Botrytis fungus has developed mist. Use of a spreader sticker to increase can be applied to weed-free soil around Rhizoctonia lesions are more defined, with resistance to several major classes of chance of contact with the pest is recom- growing plants in the spring to control tan, sunken areas. Sometimes the light chemical fungicides, including the benz- mended. Check with your local spring-germinating annual weeds. The tan, fine “cob web” mycelium of imidazoles (e.g., Cleary’s 3336 and Cooperative Extension office for current- preemergent Dacthal prevents germina- Rhizoctonia can be seen on blighted plant Domain) and the dicarboximides (Chipco ly labeled miticides. Usually, the best tion of several annual weed grasses and a parts and growing across the soil surface. 26019), making chemical control diffi- action is to destroy infested plants before few broadleaf annual weeds. The preemer- cult. When extended periods of wet over- the problem spreads in the planting. gent Pennant is effective against annual To differentiate Pythium from cast weather occur, it may be helpful to grasses, yellow nutsedge, and several Rhizoctonia, use an Alert on-site diagnos- spray with mancozeb or use Exotherm broadleaf annual weeds. Check with your tic kit. This will permit you to select the Termil smoke in the greenhouse. The cop- Weed Control local Cooperative Extension Service for correct fungicide for control. per fungicide Phyton 27 is also registered current recommendations on other pre- for Botrytis control on flowers. To maximize both floral quality and emergent herbicides labeled for use in Basic good horticultural practices, sani- quantity, weed control is essential in field-produced cut flowers. tation, and providing optimum condi- both field and inground greenhouse pro- tions for seed germination and seedling Powdery mildew duction of larkspur. Competition for Glyphosphate (sold under several growth can prevent most damping-off Some larkspur cultivars are susceptible nutrients, moisture, and light can be brand names, including Round-up) can losses. Selecting a well draining media to powdery mildew caused by the fungus reduced with a good weed control pro- provide postemergent control of grasses and watering early in the day so soil Erysiphe polygoni. Symptoms include gram. In a greenhouse, soils can be steam and broadleaf weeds. Apply a 33 percent drains well before nightfall helps control twisted and distorted foliage and white sterilized at 160 °F for 30 minutes to kill Glyphosphate solution with a wick appli- Pythium. SoilGard, a biological fungicide, spots and patches on foliage, stems, and most weed seeds. A weed barrier of 2- to cator. Use extreme caution with this solu- can be added to media to provide excel- buds. Flower buds may fail to open and 4-mL black plastic with holes made for tion. Be careful not to make contact with lent control of both Pythium and flowers may be distorted and unsalable. placement of plant plugs or seeds can the larkspur or the Glyphosphate will kill Rhizoctonia. Weather conditions that favor powdery greatly reduce the need for weeding. your desired plants as well as the weeds. mildew are sunny, warm, dry days, and Unfortunately, the black plastic tends to Botrytis blights cool nights. cause the soil temperatures to rise, which Some growers have used methyl bro- will affect the quality of the larkspur mide to fumigate the soil before direct Botrytis can attack seedlings, but it is Several systemic fungicides (e.g., crop. A light layer of leaves or bark can seeding of larkspur. Used for years, this especially damaging when it spots and Funginex, Terraguard, Strike, Banner) and be laid over the black plastic to reduce soil fumigant kills weeds, seeds, and blights flowers. High humidity and a film summer oil sprays all provide good con- the heat buildup. many insect and disease species. It is of water on plant surfaces is necessary for trol of powdery mildew. Some larkspur presently still available for use by certified Botrytis to infect plant tissues. Thus, any cultivars are less susceptible. Keep good Another option for weed control is to pesticide applicators, but is being phased cultural practice that reduces periods of records of disease incidence on each culti- use organic mulch as a surface applica- out of the market because it is extremely leaf wetness (trickle irrigation, plant spac- var you grow; you can then select resis- tion. If seeding is done in the fall, a 1- toxic. Basamid (granular formulation) can ing to improve air circulation, use of hor- tant cultivars. inch organic mulch layer (composted also be used as a soil fumigant and is izontal air flow fans in greenhouses, etc.) leaves or grass clippings) can be applied much safer than methyl bromide. will reduce the risk of Botrytis. Southern blight close to the plants after they germinate. The mulch layer will reduce germination Botrytis produces a small, defined spot The Southern blight fungus Sclerotium of fall-germinating weeds. In the spring, that may rapidly enlarge to blight the rolfsii (also called Sclerotium delphini by if the organic mulch layer has thinned flower, leaf, or stem. Weak plant tissues some authors) can be a serious problem in out, an additional 1-inch layer can be Harvesting Larkspur such as yellowing senescent foliage, field-grown larkspur during hot weather. flower petals, and wounds are easily The fungus remains in the upper inches placed on the soil to reduce germination Fresh market sales of spring-germinating weeds. invaded by Botrytis. Under humid condi- of field soil and is only active during peri- Larkspur flowers start opening from the tions a gray mold is produced on blighted ods of hot weather when soil tempera- A chemical option to prevent annual bottom and progressively open up from tissues. This gray mold is diagnostic of tures rise into the upper 70s. The fungus weeds from germinating would be to the flower stem to the top. For fresh mar- Botrytis. Look for this aerial gray mold attacks the plant at the soil surface, caus- apply a preemergent herbicide. The pre- ket sales, harvest when several lower early in the morning or incubate dam- ing a rapid wilt and crown rot of individ-

8 5 Cultivars blooms have fully opened. If shipping the the flowers by hanging flower stems flowers, try to harvest before the lower upside down and drying at 70 to 80 °F for •Consolida orientalis: one-third of the flower stem has opened. 10 to 14 days. A well-ventilated drying Giant Imperial series—The standard For direct markets, you may choose to barn is ideal for preserving larkspur. of the industry. Plants grow 3 to 4 harvest when one-half to three-quarters feet tall. Colors: carmine, deep blue, of the flower stem has opened. The vase deep rose, light blue, lilac, pink, Postproduction Factors salmon, and white. life of larkspur is between 5 to 7 days. The flower blooms are highly sensitive to Messenger series—Plants are 3 to 4 ethylene and will shatter in its presence. feet tall and flower 2 weeks earlier Retail handling than the Giant Imperial series. To hold larkspur for 1 to 2 days, place stems in fresh water, keeping them • Recut stems. After bringing larkspur Colors: Blue, lilac, rose, and white. in from the field, recut stems under upright and maintaining temperatures of Early Bird series—Earlybird flowers water to prevent a water uptake 2 to 3 weeks earlier than Giant 34 to 40 °F. blockage. Imperial. Plants are 3 to 4 feet tall. • Ethylene. Flowers are highly sensi- Colors: blue, lilac, rose, white, and Everlasting sales tive to ethylene, with resulting pre- mixed. mature dropping of flowers. Flowers Larkspur are relatively easy to dry for QIS series—Very uniform plants and will react when exposed to ethylene thick stems. Plants grow 2 to 3 feet sale as everlasting flowers. For everlasting at 3 ppm for 24 hours at 70 °F. tall. Colors: carmine, dark blue, light flowers, harvest when the majority of the Causes include shipping with mixed- pink, lilac, rose, white, and mixed. flowers have opened, but before the bot- fruit or decaying plant material. tom flower petals have dropped. The feathery foliage does not need to be removed when dry- Pests ing the flower stems. Air dry

Major Diseases The most important diseases of larkspur cut flower production are damping off of seedlings (Pythium and Rhizoctonia fungi), Botrytis, powdery mildew, and Southern blight.

4 9 • Pretreatment. Pulse with silver thio- tures below 55 °F for 4 to 6 weeks before devices that monitor soil moisture and sulfate (STS) to minimize ethylene being moved into the field in April. can be used to help the grower decide damage and prolong vase life. Use a Yields of cut flowers seed-started in green- when to irrigate. (For more information, commercial silver solution according houses are generally not as heavy as refer to University of Maryland Extension to label directions, preferably for a 1- yields from plants field-started in the fall. to 2-hour treatment. The STS solu- Service Bulletin 312, ”Soil Moisture tion must be processed for silver Sensors for Irrigation Management.”) recovery before it can be disposed of Site selection down a drain. Commercial devices, Select a location that receives at least 8 Nutrition such as a Superbatcher, are specially hours of direct sunlight. A source of designed to remove the silver from Adding a 1- to 2-inch layer of compost- STS. water near the site is good because an irrigation system is frequently needed for ed organic material and tilling it in will STS is not very stable, giving the greatly benefit larkspur growth. Larkspur solution a relatively short shelf life. best quality production. Larkspur grows Unfortunately, it is not always easy best in well-drained soil with a pH of 6.0 plants also respond favorably to applica- to determine whether your STS solu- to 7.0. Using a raised bed improves tions of nitrogen fertilizer. If using trickle tion is still active. Test kits are avail- drainage and will also warm the bed earli- irrigation, fertilize on a weekly basis with able to test the solution’s effective- er in the spring. Wide spacing of 10 to 12 100 parts per million (ppm) of complete ness. inches between plants will provide more fertilizer based on nitrogen. Water-driven • Hydration. Hydrate in clean, warm cut flower stems per plant. The yield per fertilizer injectors are available that add water (80 to 90 °F) at pH 3.5 to 4.0. square foot will increase with a closer the correct proportion of concentrated • Preservation. Use a floral preserva- spacing of 4 to 5 inches between plants, soluble into the irrigation water. If pro- tive for maximum longevity. but will decrease per individual plant. ducing larkspur without trickle irrigation, • Temperature. Refrigerate at 35 to side dress with a complete fertilizer (10-5- 40 °F. Support 10 or 10-6-4 ratio) at 1 pound per 100 Most larkspur cultivars grow to a square feet of production row. height of 3 to 4 feet. Unsupported flowers will often fall over with the stems turning upward. To maintain the quality of cut Greenhouse Production flowers, one or two layers of net or wire Larkspur is best grown in groundbeds support (6- to 8-inch openings) are rec- to facilitate production and harvesting. ommended to help hold flowers upright. The seeds should be sown from Irrigation September through November. Maintain temperatures at 50 to 55 °F for 8 to 10 Installing a trickle irrigation system is a weeks. Raise temperatures to 55 to 60 °F worthwhile investment. Irrigation is best after this time. Larkspur needs day achieved using irrigation rowcrop tape or lengths of 16 hours to flower. The day rowcrop emitter tubing that lies down length can be extended with lighting or the row with emitters spaced 6 to 12 inches apart. Two or three rowcrop tapes with 2-hour night break lighting using on a raised bed will water several rows of incandescent lamps. plants across the bed. Coarse soils need more tapes. Water frequently enough to Nutrition maintain a good soil moisture. Use a screen filter of 100 to 140 mesh to pre- Greenhouse-grown larkspur needs vent clogging and use a small pressure weekly applications of a dilute soluble regulating device set at 8 to 10 psi to complete fertilizer (for example, 20-10-20 ensure the proper operating pressure for or 15-5-15 ratio) at 100-200 ppm based the trickle tubing. Tensiometers are on nitrogen.

10 3 established in the fall grow rapidly in Larkspur seed does not germinate well Consumer Care cool, moist springs, with heavy flower when soil temperatures are held above production in May and June and occa- 75 °F. Germination will be improved by • Recut stems under water and place sionally into July if the weather remains chilling seed (35 to 40 °F) for at least 7 to flowers in clean warm water contain- favorable. 14 days prior to planting. In Maryland, ing a floral preservative. optimum seeding times for field produc- • Avoid temperature extremes such as The genus of larkspur was recently tion are from September through heavy freezing or temperatures over 95 °F. changed from Delphinium to Consolida. frost. Most growers will plant a series of • Keep flowers away from rapid air Two species of larkspur are used for cut sequence plantings at 2-week intervals. movement. flowers: Consolida ambigua and Consolida Germination takes place 12 to 20 days orientalis. C. orientalis is more upright • Avoid keeping flowers near ripening after sowing. Once the seed has germinat- fruit, which emits ethylene. than C. ambigua, and colors are often ed, the larkspur plants will grow rapidly shades of bright pink and purple. C. in cool fall weather. Larkspur plants plant- ambigua have more branches initially and ed in fall flower 4 to 6 months after plant- colors are usually light pink or blue. Most ing. of the outstanding larkspurs for cut flower production are C. orientalis vari- eties.

Culture

Field Production

2 11 References Reviewed by Armitage, Allan M. 1993. “Specialty Dr. John Dole, Oklahoma State Cut Flowers.” Athens, GA: Varsity Press, University Producing Larkspur as Cut Flowers Inc. Dr. Will Healy, George Ball Seed Gill, Stanton A. and J. Sanderson. 1997. Company, Inc. “Ball Greenhouse Pest Identification and Fact Sheet 713 IPM Control.” (In press.) Illustrations by Nau, Jim. 1995. “Ball Perennial Raymond Bosmans, Regional Specialist, Manual: Propagation and Production.” CES Home and Garden Information Batavia, Illinois: Ball Publishing. Center Powell, Charles and Richard Linguist. 1992. “Ball Pest and Disease Manual: Disease, Insect, and Mite Control on Flower and Foliage Crops.” Batavia, Illinois: Ball Publishing. Note: When trade names are included, no dis- Woods, Christopher. 1992. crimination against similar products is intended. “Encyclopedia of Perennials.” New York Mention of trademarks in this publication does not constitute an endorsement by the Cooperative City: Facts on File, Inc. Stanton Gill Introduction Extension Service. regional Extension specialist Central Maryland Research and Education Center Larkspur, Consolida spp., are excellent cut flowers—both for fresh and dried or Ethel Dutky plant pathologist everlasting markets. Many cut flowers are Department of Entomology popular for short periods of time, often University of Maryland at College Park attracting public attention for less than 5 years, then fading from demand. The Russell Balge market for good quality larkspur has been regional Extension specialist strong for many years, past the period of Western Maryland Research and Education Center “fad flowers,” and it continues to stay Tom Blessington robust. The alluring flower shape, wide regional Extension specialist range of colors, and appealing foliage all Central Maryland Research and Education Center combine to make larkspur a popular, mar- ketable cut flower. The flowers tend to be David Ross somewhat fragile and relatively short- Extension agricultural engineer lived in the vase (under 7 days), making Department of Biological Resources Engineering production for local markets very appeal- University of Maryland at College Park ing. Bryan Butler faculty Extension assistant Larkspur grow to their full potential in Carroll County climates with cool, moist summers. Growers must adopt practices that take Ginny Rosenkranz advantage of the cooler seasons to suc- faculty Extension assistant cessfully grow larkspur as a cut flower Wicomico and Worchester Counties crop in Maryland. Maryland growers Suzanne Klick often establish sequence plantings of commercial horticulture technician larkspur during the cool weather of Central Maryland Research and Education Center September through heavy frost. Plants P97 Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30,1914, in cooperation with the U.S. Department of Agriculture, University of Maryland at College Park, and local governments. Thomas A. Fretz, Director of Cooperative Extension Service, University of Maryland at College Park. The University of Maryland is equal opportunity. The University’s policies, programs, and activities are in conformance with pertinent Federal and State laws and regulations on nondiscrimination regarding race, color, religion, age, national origin, sex, and disability. Inquiries regarding compliance with Title VI of the Civil Rights Act of 1964, as amended; Title 12 IX of the Educational Amendments; Section 504 of the Rehabilitation Act of 1973; and the Americans With Disabilities Act of 1990; or related legal requirements should be directed to the Director of Personnel/Human Relations, Office of the Dean, College of Agriculture and Natural Resources, Symons Hall, College Park, MD 20742.