Ho! Ho! Ho! Merry Christmas Senna1 by Ken Langeland UF/IFAS Agronomy Department & Center for Aquatic and Invasive Cooperative Extension Service Introduction into the wild. Because of the confusion in , everyone may not realize that Christmas must be just around the the plants for sale in the nursery trade are corner because home landscapes are col- the same as those escaped and ored with the bright yellow of growing in the wild. This article will pro- Christmas ( var. vide information on the biology of glabrata). Christmas senna is a long time Christmas senna outside of cultivation favorite landscape , commonly culti- and clarify the taxonomy. vated as an ornamental in Florida at least since the 1940s (Bailey and Bailey 1947). Christmas senna is so named because it Distribution blooms during the Christmas season (Fall- Christmas senna is native to Brazil, Fig. 1 Winter). It is popular, in part, because of Peru, Bolivia and south to Paraguay and its showy yellow flowers (Fig. 1). This is Argentina. It is cultivated in warm regions especially true in the northern part of the of both hemispheres. In the US it occurs in state, where it is one of the few landscape Florida, Texas (common in southern plants that bloom in late fall and early win- Texas), California, Arizona, and probably ter. It also is popular for butterfly gardens in other Sunbelt states (Isely 1998). It is (Fig. 2). Christmas senna also is known as cultivated in all regions of Florida (Hunt Christmas , winter cassia, climbing 1977, Nelson 1996). Herbarium records cassia, cassia , butterfly cassia, but- document it as outside of cultivation from terfly bush, or just plain cassia. The com- Hillsborough and Brevard Counties south mon name “cassia” is derived from the to Dade and Collier Counties (Wunderlin Cassia, to which the species histori- et al. 2003). It is reported from scrub and Fig. 2 cally belonged. “Climbing” describes the forest natural areas in Palm Beach County plant’s clambering growth habit when sup- and from the edge of Lake Okeechobee in port is available, while “shrub” refers to its Hendry County (EPPC 1996). In Collier growth habit in open ground. In the nurs- County, it invades mangrove communities ery trade it is known by the botanical name at the headwaters of the Baron River (per- of Cassia bicapsularis. sonal observation by the author). It was Christmas senna can be seen bloom- reported as a weed of canal banks, road- ing not only in landscapes, but also along sides, and fencerows in 1977 (Orsenigo roadsides, canal banks, hammocks, marsh- 1977). It has been observed in the wild in es, and even mangrove communities. It south Florida since the early 1970s (D. F. escaped from cultivation and has become a Austin, Florida Atlantic University, 1995 weed in natural areas and other sites in personal communication). It is noted as Fig. 3 central and southern Florida (Fig. 3). naturalized in south Florida and becoming Those traveling the state by car will espe- weedy in the Bahamas and disturbed areas cially notice the brilliant yellow flowers in (Irwin and Barneby along commonly traveled roads such as 1982). Isely (1990) described it as moder- Florida’s turnpike south of Orlando, I-75 ately established outside of cultivation in south of Sarasota, and SR 60 between Florida. Yeehaw Junction and Vero Beach. The virtues of Christmas senna as an Natural History ornamental landscape plant have been Christmas senna produces flowers well described (e.g. Dirr 2002; Gilman from October through January. Large num- and Black 1999; Bender and Felder bers of seeds are produced, which mature 1993). Little, however, has been pub- through the spring and summer. Seeds lished concerning the escape of this plant may be dispersed by continued on page 12 Fig. 4

1. The invasive characteristics of this plant have not been assessed using the IFAS Assessment of Non-Native Plants in Florida’s Natural Areas.

WILDLAND WEEDS 11 Merry Christmas Senna continued undisturbed areas of Florida’s tropical ham- Botanical Description mocks, coastal strands, and canal banks (M. birds, mammals, and/or human con- Christmas senna is a sprawling ever- Renda, The Nature Conservancy, 1996 per- veyance but specific dispersal agents have green shrub to 4 m (13 ft) tall (or wide), sonal communication). not been identified. Plants are hardy north with somewhat zigzag, sparsely hairy of the frost line as they will regrow after Taxonomy stems. are alternate, stalked, even- tops are killed by freezing (Maxwell and pinnately compound, with 4 to 7 pairs of The genus Senna ( ) is Maxwell 1961). Specimens (reported as C. leaflets, the larger ones occurring at the represented by ten species in Florida, four bicapsularis) over 3 m (10 ft) are common tip. The leaflets are up to 4 cm (1.6 native and six introduced (Wunderlin as far north as Charleston, South Carolina in) long, oblong with rounded tips; leaf 1998). The correct nomenclature for the (Dirr 2002). The lack of herbarium records stalks (petioles) have a gland on the Florida plants called by the common name north of Hillsborough and Brevard upper surface, between lowermost Christmas senna is Senna pendula (Willd.) Counties suggests that the plant has not leaflets (and occasionally between oth- Irwin & Barn. var. glabrata (Vogel) Irwin escaped or effectively reproduced out of ers). The flowers are yellow or yellow- & Barn. ( Cassia colutoides). This cultivation in colder of the state. green, 3 to 4 cm (1.2 to 1.6 in) across, in revised nomenclature is based on the sepa- Plants may not produce viable seed when 3- to 12-flowered near the stem ration by Irwin and Barnaby (1982) of the they are frozen back in winter, which is a tips. in the flowers have promi- large genus Cassia into Cassia, Senna, and possible explanation. However, sexual nent, curved filaments (Fig. 4). The fruit based on male floral reproduction has been observed as far is a brown slender pod, cylindric, characteristics. north as Gainesville (David Hall, 2003 per- glabrous, 7 to 12 cm (3 to 5 in) long. sonal communication). Whether the Christmas senna plants found in culti- species can become as abundant in the vation or established in Florida usually Control have been identified as Cassia bicapsularis, northern part of Florida remains for future Christmas senna can be controlled by which they are not (Isely 1998). The determination. foliar or basal bark herbicide application. species Cassia bicapsularis, now properly Christmas senna often becomes estab- The following foliar applications on a called (L.) Roxburgh, lished in sunny openings and then clambers spray-to-wet basis have been found effec- has been only slightly introduced into the over adjacent vegetation (Austin 1998). It tive: 1.0% Roundup Pro, 0.5% Garlon 3A United States and is not known to have displaces native plants in both disturbed and + 0.375% Induce, 0.50 oz/gal Escort + escaped in Florida (Isely 1990). Senna 0.375% Induce, 3.13% Brush-B-Gon. bicapsularis has leaflets in 3 pairs and Basal bark application of 10% Garlon 4 in stalks (pedicels) 3-5 mm (0.12-0.2 oil is used by the Southwest Florida Water For the plants you in) long, while the commonly escaped Management District (Mack Sweat, 2003 Senna pendula has leaflets in 4-7 pairs and love to hate… personal communication). flower stalks (pedicels) 2 cm (0.08 in) or more long (Isely 1998). The species name pendula describes the growth habit of the For more information, contact Ken Langeland at Pandion [email protected] Systems, Inc. branches, which arch downward. Literature Cited Austin, D.F. 1998. Invasive exotic climbers in Florida: Biogeography, ecology, and problems. Fla. Scientist 61: 106-117. Invasive Exotic Plant Bailey, L. H., and E. Z. Bailey. 1947. Hortus Second. Macmillan Co., New York. 778 pp. Management Bender, S. and F. Rushing. 1993. Passalong Plants. University of North Carolina Press, Chapel Hill. 221 pp. Dirr, M. A. 2002. Dirr’s and for Warm Climates: An Illustrated Encyclopedia. Timber Press, Portland, OR. 448 pp. EPPC. 1996. Florida Exotic Pest Plant Council occurrence data base. Unpublished. Data available by requests via Web site: Ecologists and land http://www.fleppc.org/. Gilman, E. F. and R. J. Black. 1999. Your Florida Guide to Shrubs Selection, Establishment, and Maintenance. University managers… Press of Florida, Gainesville. 116 pp. Hunt, S. 1977. Dig Manual: Guide to Identification and Selection of Florida Ornamental Plants. Fla. Dept. of Education, Specializing in complex Career Education Center, Fla. State Univ., Tallahassee. 224 pp. control and research projects Irwin, H. S., and R. C. Barneby. 1982. The American Cassiinae: A Synoptical Revision of Leguminosae tribe Cassieae subtribe Cassiinae in the New World. Mem. New York Bot. Gard. Vol. 35, Part I. 454 pp. requiring a high degree of Isely, D. E. 1990. Leguminosae (Fabaceae). Vascular Flora of the Southeastern United States, Vol. 3, Part 2. Univ. of North ecological proficiency and Carolina Press, Chapel Hill. 258 pp. Isely, D. E. 1998. Native and Naturalized Leguminoseae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). experience. Monte L. Life Science Museum, Brigham Young University, Provo, UT. xi, 1007 p. Maxwell, L., and B. M. Maxwell. 1961. Florida Plant Selector. Maxwell Publ., Tampa. 116 pp. Nelson, G. 1996. The Shrubs and Woody Vines of Florida. Pineapple Press Inc., Sarasota. 391 pp. Gainesville, Florida Orsenigo, J. R., D. S. Burgis, W. L. Currey, D. W. Hall, W. T. Scudder, T. J. Stelter, and D. B. Ward. 1977. Florida Weeds, Part II, A Supplement to Weeds of the Southern United States, Circular 419. Florida Cooperative Extension Service, Institute of 352-372-4747 Food and Agricultural Sciences, University of Florida. Gainesville. 19 pp. www.pandionsystems.com Wunderlin, R. P. 1998. Guide to the Vascular Plants of Central Florida. University Press of Florida, Gainesville. 806 pp. Wunderlin, R. P., and B. F. Hansen. 2003. Atlas of Florida Vascular Plants (http://www.plantatlas.usf.edu/).[S. M. Landry and [email protected] K. N. Campbell (application development), Florida Center for Community Design and Research.] Institute for Systematic Botany, University of South Florida, Tampa.

12 WINTER 2003 Evaluation of Foliar Applied Herbicides for Control of Christmas Senna1

Langeland, K. A., D. W. Clark, R. K. Stocker, and G. E. MacDonald; UF/IFAS Agronomy Department & Center for Aquatic and Invasive Plants

Introduction were overhead irrigated every other day and Table 1. Control (%defoliation) of Christmas senna weeds were controlled by tilling and spot Christmas senna (Senna pendula eight months after foliar herbicide applications (all spraying with a glyphosate containing herbi- additions of Induce, an adjuvant, at 0.375%). (Willd.) Irwin & Barn. var. glabrata (Vogel) cide. Plants grew vigorously and attained 1.5 Irwin & Barn.) has been commonly cultivat- Treatment % Defoliation to 3.0 meters in height. ed as an ornamental in Florida at least since 0.750% Transline + Induce 100 0.500% Transline + Induce 100 the 1940s (Bailey and Bailey 1947). It HERBICIDE APPLICATION 0.250% Transline + Induce 100 escapes from cultivation in central and Herbicides were applied November 9- 0.125% Transline + Induce 100 southern Florida and has become a weed in 10, 2001. Weather during and immediately 1.000% Garlon 3A + Induce 100 natural areas and other sites. It was reported after herbicide application was clear, calm, 0.500% Garlon 3A + Induce 100 as a weed of canal banks, roadsides, and 0.250% Garlon 3A + Induce 95 and 78 F. Herbicides were applied on a fencerows in 1977 (Orsenigo 1977) and has 0.063% Garlon 3A + Induce 82 spray-to-wet basis, which resulted in appli- been observed in the wild in south Florida 0.020 oz Escort/gal + Induce 100 cation of approximately 0.75 l of spray solu- since the early 1970s (D. F. Austin, Florida 0.010 oz Escort/gal + Induce 100 tion per plant. Each herbicide treatment 0.025 oz Escort/gal + Induce 91 Atlantic University, 1995 personal commu- (Table 1) was applied to 10 randomly 0.012 oz Escort/gal + Induce 77 nication). It is noted as naturalized in south assigned replicate plants. Induce (Helena 2.0% Roundup Pro 100 Florida and becoming weedy in the Bahamas Chemical), a nonionic fatty acid based sur- 1.5% Roundup Pro 100 and disturbed areas in South America (Irwin 1.0% Roundup Pro 100 factant, was added to spray solutions of and Barneby 1982). It often becomes estab- 0.5% Roundup Pro 98 Transline, Garlon 3A, and Escort. Water, lished in sunny openings and then clambers 3.13% Brush-B-Gon 100 containing no herbicide or adjuvant, was 1.95% Roundup Super Concentrate 59 over adjacent vegetation (Austin 1998). It applied to experimental checks. Untreated check 56 displaces native plants in both disturbed and undisturbed areas of Florida’s tropical ham- EVALUATION 0.012 oz/gal) resulted in good to fair control. mocks, coastal strands, and canal banks (M. Final evaluation for herbicide efficacy Roundup Super Concentrate at 1.95% pro- Renda, The Nature Conservancy, 1996 per- was determined on July 10, 2002 (eight vided no control of Christmas senna. sonal communication). The purpose of this months post application) as percent of Transline contains the active ingredient study was to evaluate herbicides for control foliage that was defoliated or attached and clopyralid, which is known to have excellent of Christmas senna. completely necrotic. Foliage that contained herbicidal activity on other leguminous any green tissue was not considered weeds such as kudzu. It is not registered in Materials and Methods necrotic. Florida but is scheduled to be registered in PLANT CULTURE counties of western Florida (Scott Christmas senna seeds were collected in Results and Discussion Ditmarsen, Dow AgroSciences, 2003 per- January 2000 from plants growing along a All rates of Transline (0.750% to sonal communication). roadside in Lee County, FL. In May 2000, 0.125%), Garlon 3A at 1.0% and 0.5, Escort Brush-B-Gon, is a dilute product of seeds were removed from the pods, scarified, at 0.02 and .01 oz per gallon, Roundup Pro triclopyr (0.75 lb a.e./gal), which is pack- and germinated in moist petri dishes. Upon at 2.0%, 1.5%, and 1.0%, and Brush-B-Gon aged for homeowner use and available in reaching a height of 4.0 to 8.0 cm (1.6 to 3.2 at 3.13% gave complete control of Christmas small containers in retail garden supply in), seedlings were planted in one-gallon senna (Table 1). Plants were completely stores. The dilution used in this study is containers of commercial topsoil in a plastic defoliated, woody plant parts were desiccat- that recommended on the Brush-B-Gon house at the UF/IFAS Center for Aquatic and ed and brittle, and plants showed no indica- label. The concentration of active ingredi- Invasive Plants in Gainesville, Florida. tion of regrowth. In contrast, untreated ent in this Brush-B-Gon dilution is in Seedlings were allowed to grow from June plants were defoliated 56% by cold damage between the 1.0% and 0.5% dilutions of 2000 through April 2001, during which but were vigorously regrowing at the evalua- Garlon 3A, which is a concentrated (3 lb time they were transplanted to 2.5-gallon tion time in July. Roundup Pro at 0.5% a.e./gal), commercial product. containers. The plants were removed from resulted in excellent control with nine of ten Roundup Super Concentrate is a containers and planted on two-foot centers replicate plants being 100% defoliated. glyphosate containing product that is pack- at the IFAS Agronomy farm (Green Acres) Lower rates of Garlon 3A (0.25% and aged for homeowners and available in retail near Citra, Florida in April 2001. Plants 0.063%) and Escort (0.025 oz/gal and garden supply stores. It is more concentrat- 1. The invasive characteristics of this plant have not been assessed using the IFAS Assessment of Non-Native Plants in Florida’s Natural Areas.

WILDLAND WEEDS 13 Foliar Applied Herbicides continued FLEPPC Board Gets Down and Dirty ed (3.7 lb a.e./gal) than Roundup Pro (3 lb a.e./gal), which is packaged The most recent quar- for commercial applicators. The terly meeting of the concentration of Roundup Super FLEPPC Board of Concentrate used (1.95%) is between Directors took place at the two highest concentrations of Fort Jefferson National Roundup Pro used and would be Monument in the expected to perform as well based on Dry Tortugas National herbicide rate. The lack of control Park, 70 miles west observed with Roundup Super of Key West, Florida. Concentrate compared to Roundup Following up on the 1995 exotic plant Pro may be related to adjuvants in the management plan that FLEPPC helped different formulations (proprietary develop, board members spent several information) but cannot be explained hours removing exotic Agave plants in this study. from Loggerhead Key. It was a prickly job and drew blood from several of us, Acknowledgements but our time was well spent. During a Appreciation is expressed to Mike sweep of the island, we pulled or treated Ward, Elizabeth Jimenez and Hillary Agave plants regrowing from an estab- Cherry for technical assistance, and to lished population that was removed in Helena Chemical, DuPont Agricultural the late 1990s along with Australian Products, Monsanto Company, and pines (Casuarina equisetifolia) (see arti- Dow AgroSciences for herbicides or cle by Tony Pernas, et al, Wildland adjuvants used in this study. Weeds, Winter 2001). – Ed.

For more information, contact Ken The tenacious Jonathan Taylor of the Langeland at [email protected] National Park Service organized the FLEPPC board member agave pull.

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14 WINTER 2003