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Home , Mertensia, Pulmonaria, Subshrub

PROPAGATING HERBACEOUS PERENNIALS IS IT REALLY THAT MYSTERIOUS? David J. Beattie, Department of , Penn State University

Introduction instance, Heucheramicrantha 'Palace Purple' is prized for its rich, bronzefoliage. It iseasily propagated byseedand The use of herbaceous perennials continues to be one of does notrequirestratification. Eventhough it has a thefastestgrowing segmentsofornamental horticulture, namethatimpliesuniformity, greenoroff-colorvariantsare but much mystery still surrounds their propagation and regularly produced and must be rouged out. If this is not culture. Although the basic principles of propagating done rigorously, manyofftypes enterthe market. Forthe herbaceous perennials are similarto woody , many mostdesirable plantsthough, selectionsshould be madeof of the specific practiceshave been proprietary; thatis, the the besttypesand theyshould beasexuallypropagated. In methods have resided in the experience of a few master contrast, Campanula carpatica 'White Clips' is alsopropa propagatorswhoseinformation has been passedfrom one gated by , but the populations are very uniform, so generation tothe next. In addition, since many perennial there is no practical reason to propagate it asexually. nurseries haveseveralthousand taxa, it is understandable thattheexactpropagation methodsfor manytaxa maynot Someperennial seed, especiallythose in the peafamily like be well known. However, with more perennials being Baptisiaaustralis, have hard-coated seedsthat, when dry, grown, there is less mysterysurroundingthe propagation do not allowwatertoeasilyenterthroughthe seedcoatto of these popular garden plants and the information is begin initiating the process. Baptisia seed generally more available. germinateseasilyifit is sownwhentheseed is fully ripe, but before it is allowed to dry out. If the seed dries out, seed Herbaceous perennials grown above ground during the coats must be broken down in a process called scarifica growing season, but with the onset of short days and tion. This is accomplished byeitherrubbingthe seed lightly freezing weatherthetops die, and the retreats to an betweentwo layersofsandpaperor by immersing theseed underground . These storage organs as for 15 minutes in concentrated sulfuric acid. Usually no sume many sizes, shapes, and names. They may be further treatment, such as stratification is necessary. fibrous rooted structures, , tuberous , tubers, , stolons, crowns, orpips, andfunction as reser The perennial industry has experienced rapid growth in the voirs ofgrowth regulators, water, and nutrientsthat propel lastfew years, resulting in customerswho no longerwant the plantsinto growththefollowing season. Thesestorage common seed-propagated plants like Shastadaisy, butare units can be lifted, stored, shipped, and can serve as the looking for named . The resultis that, while seed basic propagating units. propagation willalways beimportant, greateremphasis will be placed on asexual methods to propagate the new My objective is to discuss some of the principles and cultivars. practices of propagating herbaceous perennials, concen trating on rootcuttings and division. Only one important TIP CUTTINGS: Many popular genera of peren is propagated bygrafting; seedand shoottip propa nials like Artemisia, , Coreopsis, Lavendula, and gation will be lightly covered, and culture propaga Delphinium can be propagated by shoottip cuttings. The tion has been, and will be, adequately covered by other principles and methods are similar to those for woody speakers. plants. One significantdifferencefrom woodycuttingsis thatlittle orno rooting hormone is necessary. If it is used, SEED: The majority - perhaps more that 50% - of all it is usually the equivalent of Hormodine #1 (1000 ppm herbaceous perennials are propagated by seed. Seed IBA). Anotherdifference is that perennial cuttings, since propagation has both advantagesanddisadvantages. The they are soft, non-woody tissue, are more susceptibleto seed is a relatively inexpensive propagation unit, easily rotting in the propagation bench. This is easily overcome stored, and is well adapted tothe automation provided by either by reducing the misting frequency, or by covering the seeding machines. Forthis reason propagating perennials plants with rowcovermaterial. Thiscoveris a thin, white, is becoming increasingly popularfor bedding plantgrow light-weightfabric. Itis routinely used by European grow ers. Since herbaceous perennial generally do not ers who prefer covering freshly-stuck herbaceous cuttings have as long or as deep of dormancy as do woody seeds; with thisfabric to placing them in a mist bed. stratificationtimesare usually shorter. However, seedsof someperennialstendto beshorter lived than their woody Cuttings of herbaceous perennials are of two types. The counterparts, and the biggest problem facing perennials mostcommon is thetip cutting which is taken atthetip of propagators is the industry-wide problem oflocating high elongated growth as is done with a woody . Aster, quality, true-to-nameseed. Chrysanthemum (Dendranthemum) and Tricyrtis can be propagated bythis type of cutting. Incontrast, thegrowth Seed propagation has several disadvantages. Seed propa of other plants WkeArmeria, Geranium and Achilleado gated plants may have many different phentotypes. For not provide an elongated, well-defined cutting. Here the

Georgia Commercial Rower Growers Association Newsletter • January - February, 1994 • Page 16 cutting must be taken early in the growth cycle when the pack flats. The flats are then placed in a high humidity shootis short, often with several attached roots. This type chamber in a shaded portion of a 60°Fgreenhouse where of cutting, sometimes referred to as a "rooted cutting," often they can be observed for rooting. As each cutting or group requires minimal misting and establishes quickly. of cuttings develop and begin to , they are removed and transplanted. In the second method, the The second type of herbaceous perennial cuttings is rep cuttings are packed in rows into a 3 to 4" deepflat. Theflat resented by easy-to-root plants likePhysostegia, Chelone, is placed on the bench at a 45 degree angle, and alternate Monarda, and many mints which can be rooted by - layers ofcuttings and medium are placed each on top of the node cuttings. The entire stem can be sectioned into other until theflat is filled. Flatsfilled in this mannercan hold individual nodes, each with one or two . Although 300to 400 cuttings, depending on the root diameter. smaller than shoot tip cuttings, their increased numbers represent a way of inexpensively and rapidly increasing While the polarity of a shoot cutting is very important, it is less so with root cuttings. Even though fastest shooting plant populations. and rooting is obtained ifcuttings are oriented inthe upright, ROOT CUTTINGS: Root cuttings are a very useful proximal (with the end that was closest to the soil like method of asexual propagation, particularly for plants that position, cuttings placed in a horizontal position appear to do not produce many seeds, and have growth habits that root equally well, but require more space. produce relativelyfew divisions or cuttings. Manyplants in the Borage like , Brunnera, Anchusa, Not all plants can be propagated by root cuttings, nor is it and have these characteristics and are routinely desirable to propagate some plants by this method. For propagated by root cuttings. This method can be efficient, instance, variegated plants like Brunnera macrophylla too. Byusing a combination of root cuttings and division, Hadspen Cream' or 'Alba' can only be propagated by I have propagated nearly 100 salable-sized Pulmonaria division. When propagated by root cuttings, plants with 'E.B. Anderson' plants from three root pieces that were green leaves result. This is because the origin of the shoot approximately 10 inches long. Imaginewhat a root-bound, within the root tissue is different from the tissue that two-gallon Pulmonaria would yield! Root cuttings are resulted in the variegation. usually thought to be only for plants with thick roots like mollis, but thin-rooted perennials like Phlox DIVISION: Division is one of the simplest and easiest paniculata, summer phlox, willingly form shoots on root methods of propagate perennials like Astilbe, Hosta, cuttings also. Hemerocallis, Iris, and Paeonia. With this method, the storage organ is divided into sections, usually, but not Cuttings are usually gathered while the plants are dormant from Novemberto February. There are exceptions. Papaver orientate, the oriental poppy, goes dormant in August, so cuttings can be taken anytime thereafter. Anenome sylvestrisforms shoots on roots still attached to the plant, so they can be excised anytime after late September and transplanted. Cuttings can be gathered from plants that are GardenSmith grown in the field, but are most easily gathered from container-grown stock plants. Container-grown plants Greenhouse & Nursery have the advantage of being readily available, and no roots are lost to digging. Further, the upper or crown part of the Over 200 varieties ofherbs plant usually can be further divided or replanted. including , custom forcing, and special heirloom vegetables To prepare root cuttings, the roots are shaken free of medium and washed, if necessary. Remove the roots from We carrya large selection of the stock plant with a knife or clippers, being careful to keep spring bedding plants, perennials the roots oriented in the same direction. Next, the roots are and hanging baskets sectioned into about 1" pieces. Many books suggest making an angle cut on one to denote the proximal (nearest the soil line) or distal (end farthestfrom the soil line) end, but Wholesale / Retail some nurserymen do notfollowthis procedure, ratherthey 231 Hogan's Mill Rd. lay all the roots out in the same direction and them Jefferson, Ga. 30549 in bundles. The bundles are packed into holding flats in the 706-367-9094, FAX 706-367-9008 same proximal position and await insertion into the propa gating medium, usually in the upright position.

- Cuttings can be propagated in two distinctlydifferent ways. The easiest method is to bundle them into groups of about 15 sections and placethem in an upright position in 72-cell

Georgia Commercial Growers Association Newsletter • January - February, 1994 • Page 17 always, while the plants are dormant. Late spring, just difficult to separate. Larger and more vigorous growing before break, seems to be the best time for most, crownsoftheAstilbexarendsiiandAstilbejaponicatypes although Irisand Hemerocallis are bestpropagated during arebestdivided witha knife. Astilbesimpficifotiatypestend August, and Paeoniaduring September. Division seemsto to havemore numerous, butsmallerbuds, andcan often be be well adapted to plants that have a growth habit with separated by pulling them apart by hand. multiple oreyes produced on the storage organ. Replanting the eye at the correct depth is critical to the AST1LBE BY DIVISION: The only Astilbe that, when success of astilbe propagation. The eyes should be propagated by seed, yields reasonably homozygous popu planted at or just below soil (medium) level. With most lations is A c/w>7e/7s/s'Pumilia'. Otherwise, propagating cultivars planting a single eye in the spring should yield a astilbe from seed is not recommended. Some tissue salable sized plantwith as many as 10eyes by the end of culture laboratories have recently begun selling astilbe the growing season. A vigorous three-eye division is from shoottip cultures. While this is reasonably safe for considered to be a standard sized division ready to be cultivarswith pinkand whiteflowers, it is notrecommended transplanted into a one-gallon container. for those with red because oftheir propensity to sportnaturally. Finally,allastilbe havea crowntypegrowth PEONY BY DIVISION: Paeon/a lactif/ora, the herba habitwheretheshoots are compressed into budsoreyes, ceous peony, Wke Astilbe, is propagated by division. How so no shoots are available for tip cuttings. Thus, for the ever, there are several major differences. First, even majority of astilbe cultivars, division remains the most though many peonies are sold in containers through gar reliable methodto perpetuate cultivars. den centers, it is not a containercrop. It is bestadapted to field culture and requires two years in thefield to establish Astilbes can be propagated at almost anytime during the a vigorous plant that can be further divided. Second, growing season. However, the besttime is inearly spring, peonies can be divided only in the late summer and early before buds breakand shootgrowth begins. The second fall. It is atthistimeoftheyearwhen, withtheonsetofshort best time, and a time that many nurserymen prefer be days, buds are formed on the top of thetuberous root. cause it established a plant that can then be sold the following year, is in August. To divide peonies, the plants aredug from thefield and the root system is shaken from of soil. Then, using a stout- Astilbe is especially well adapted to containerculture, so handled knife ora pair ofshears, the rootsystem is divided container-grown plants serve as the stock plants. Best so that each division contains three or more eyes. Some resultscan beobtained ifthestockplantsarenotmorethan divisions will contain morethanthreeeyes, butthere willnot oneyearold. Thecrownson largerand olderplantsaretoo be a sufficiently large sized tuberous root to support it. woody, contain few eyes (buds), and are generally more There must be as much root as possible, although roots that are excessively long are trimmed back so that the division can be either planted to the garden or placed into a container. Replanting is especially critical to peonies. Too many woody-plant nurserymen or garden center op Fine and Unusual Perennials eratorsthatbuy peoniestryto stuffa vigorous division in a small container. Choose a large enough containersothat the buds will beabout 1" belowthe surfaceofthe medium Peonies AFTER it is watered in. English Daisies and many other GRAFTING THE PEONY: Paeonia suffruticosa, even though it is normally sold by herbaceous perennial fine perennials nurseries, is technically a subshrub. Today, it is probably now readyfor springplanting the only herbaceous perennial thatis grafted. Mostgrafts are produced in Japan and shipped to the U.S. as newly callused units. There are only a few nurseries in the U.S. BudHeist thatare presently practicingtheart of grafting to asexually (404) 483-7808 reproduced this outstanding perennial. Why are tree peonies grafted? Mostly becausethetree peonydoes not root readily and does not cometrue from seed. Heistaway Gardens, Inc. Paeoniasuffrut/cosahas small fibrous roots, so it is grafted 1220 McDaniel Mill RcL SW. on the large tuberous roots of the herbaceous peony, Paeonialactif/ora. Thelong and uniformly cylindrical roots Conyers, GA 30207 of the Klehm Estate peonies are considered the best choice. Also, the Estate Peonies do notform adventitious budsthe way otherselectionsdo.

Georgia Commercial Flower Growers Association Newsletter • January - February, 1994 • Page 18 Grafting tree peonies is done in August or September. knowledge oftiming, treatment, and method is still critical. Scions are selected from newgrowth aftertheterminal bud The major difference between woody and herbaceous hasformed. The earliest maturing P. suffruticosa hybrids perennial propagation is thatthe average perennial nursery are grafted first. Single P. suffruticosa buds are selected, grows many more taxa than its woody counterpart, thus and the leaves snipped off. Then, using a single-edged knowledge ofplants andtheirrequirementsassumes greater razor blade or retractable knife, a wedge-shaped cut is importance. made in the top end of the P. lactif/ora root, and a similar- shaped cuton base end of scion. Clean cutsare important. Reprintedfrom Proceedings 1992 PerennialPlantSympo Grafts are then wrapped so the stock and scion are held sium. closely together without danger of desiccation or disease entry. Parafilm, a thin, flexible material used in laboratories to seal petri dishes, works very well.

Since 1956 The grafts are placed in moist peat moss in plastic bags and held at about 70° F to hasten the union. They can then be CAMP & COMPANY FARMS planted in the field. This can be done in late fall in areas 2788 INDIAN SHOALS ROAD where the soil does notfreeze too deeply, or held until the DACULA. GEORGIA 30211 following spring in northern climates. Plant with the union (404) 963-0701 FAX (404) 963-3006 well below soil level so thatthe scion will be encouraged to initiate roots. After 2-3 years in the field, the plant is lifted GENE, ANN AND STEPHEN CAMP and the P. lactif/ora rootstock is removed. If not removed, itenlarges and may liftthe entire plantoutof the soil. Uncut TuieMuwdTbuw Gwum" P. lactif/ora root systems the size of footballs have been observed. One wonders what happens to the fresh grafts that are sold through garden centers to the public in the spring, poorly established and probably with no chancethat the P. lactif/ora root system will ever be removed.

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Georgia Commercial Flower Growers Association Newsletter • January - February, 1994 • Page 19 PROPAGATION METHODS FOR COMMON HERBACEOUS PERENNIALS

Stem Root Shoot tip Name Seed cuttings cuttings Division culture Acanthus spp. x xx Achillea spp. (Yarrow) x x Aconitum spp. (Monkshood) x x Aegopodiumpodagraria (Goutweed) x x Ajuga spp. (Bugleweed) x x Althaea rosea (Hollyhock) x Anemone x hybrida (Japanese Anemone) x xx Anthemis tinctoria (Golden Marguerite) XX X Aquilegia spp. (Columine) X Arabis spp. (Rock-Cress) X X X Armeria spp. (Sea Pink) XX X Artemisia spp. (Artemisia) X X Asarum europaeum (Ginger) X X Asclepias tuberosa (Butterfly Weed) X X Asperula odorata (Woodruff) X X Aster spp. (Hardy Aster) X XX Astilbe spp. (False Spirea) X XX Aubreita deltoides (Rock-cress) X Aurinia spp. (Alyssum) X X Baptisia australis X X Bellis perennis (English Daisy) X Bergenia cordifolia (Bergenia) Brunnera macrophylla (Siberian Bugloss) XXX Campanula carpatica (Carpathian Harebell) X X Campanula medium (Canterbury Bells) X

Catanache caerulea (Cupid's Dart) X X

Centaurea spp. (Cornflower) X X

Cerastium tomentosum (Snow-in-Summer) XX X

Ceratostigma plumbaginoides (Plumbago) X X

Cheiranthus spp. (Wallflower) X

Chrysanthemum x morifolium (Garden Chrysanthemum) X

Chrysanthemum x superbum (Shasta Daisy) X XX Chrysanthemum coccineum (Painted Daisy) XX X

Convallaria majalis (Lily-of-the-Valley) X

Coreopsis spp. (Coreopsis) XX X

Delphinium spp. (Larkspur) XX X

Dianthus barbatus (Sweet William) X

Dicentra spp. (Bleeding Heart) XXX X

Dictamnus albus (Gas Plant) X X

Digitalis purpurea (Foxglove) X

Georgia Commercial Flower Growers Association Newsletter • January - February, 1994 • Page 20 __ — =-Hi Stem Root Shoot tip Seed cuttings cuttings Division culture Name Dodecatheon spp. (Shooting Star; X X Doronicum spp. (Doronicum) X X Echinacea purpurea (Purple Coneflower) X X Echinops exaltatus (Globe-thistle) X X X Echinops ritro (Small Globe-thistle) X X X Erigeron spp. (Fleabane) X X X Eryngium spp. (Sea Holly) X X Euphorbia spp. (Spurge) X X Filipendula spp. (Filipendula) X X X Gaillardia x grandiflora (Blanket Flower) X X Gentiana spp. (Gentian X Geranium spp. (Crane's Bill) X X x X Geum spp. (Geum) X X Gypsophila spp. (Baby's Breath) *X X X X Helenium spp. (Helen's Flower) X Helianthemum spp. (Sun Rose) X Heliopsis spp. (Heliopsis) X X Helleborus spp. (Hellebore) X X X Hemerocallis (Daylily) X X x Heuchera spp. (Coralbells) X X X x Hibiscus moscheutos (Hardy Hibiscus) X X //asm spp. (Plantai-Lily) X X x /tern spp. (Candytuft) X X Kniphofia uvaria (Red-Hot-Poker) X X Lamium maculatum (Dead Nettle) X X angustifolia (Lavender) X X X Liatris spp. (Blazing Star) X X Limonium spp. (Hardy Statice) X X Linum perenne (Flax) X X Lobelia spp. (Cardinal Flower) X X Lunaria annua (Moneyplant) X Lupinus spp. (Lupine) X X Lychnis spp. (Maltese Cross) X X Lysimachia clethroides (Goose Loosestrife) X X Lythrum salicaria (Purple Loosestrife) X X Matricaria spp. (Feverfew) X X X Mentha spp. (Mint) X X (Bluebells) X X X Monarda didyma (Beebalm) X X X spp. (Forget-me-not) X X Nepeta cataria (Catmint) X X Nepeta xfassenii (Catnip) X

Georgia Commercial Flower Growers Association Newsletter • January - February, 1994 • Page 21 Stem Root Shoot tip Name Seed cuttings cuttings Division culture Oenothera spp. (Evening Primrose) Pachysandra terminalis (Pachysandra) Paeonia lactiflora (Herbaceous Peony) x x Papaver orientate (Oriental Poppy) x xx Penstemon spp. (Beardstongue) xx x Phlox paniculata (Summer Place) xxx Phlox subulata (Creeping Phlox) X X Physostegia virginiana (False Dragonhead) XX X Platycodon grandiflorum (Balloon Flower) X X Polemonium caeruleum (Jacob's Ladder) X X Polygonum cuspidatum (Mexican Bamboo) X Potentilla spp. (Cinquefoil) X X Pulmonaria spp. (Lungwort) X XX Pulsatilla vulgaris (Windflower) X XX Rudbeckia spp. (Coneflower) X XX spp. (Sage) X X Santolina spp. (Santolina) X Saponaria ocymoides (Soapwort) XXX X Saxifraga spp. (Saxifrage) X Scabiosa caucasia (Pincushion FIower)x XX X Sedum spp. (Stonecrop) XX X Sempervivum spp. (Hens and Chicks) X Solidago spp. (Goldenrod) X Stachys lanata (Lamb's Ear) X Stokesia laevis (Stokes Aster) X XX Teucrium chamaedrys (Germander) X X Thalictrum aquilegifolium (Meadowrue) XX X spp. (thyme) X X Tradescantia x andersoniana (Spiderwort) X

Trollius spp. (Globe Flower) X X

Verbascum spp. (Mullein) X X spp. (Speedwell) XX X

Viola spp. (Violet) X X

Walsteinia ternata (Barren Strawberry) X X

Yucca filamentosa (Spanish Bayonet) X XX SOUTHEAST GREENHOUSE CONFERENCE Qie&uulU, South GaAoluta June 16-18,1994 AND TRADE SHOW

Georgia Commercial Flower Growers Association Newsletter • January - February, 1994 • Page 22