Spigelia marilandica propagation: A Review
Winston C. Dunwell, UKREC Nursery Crops Development Center
Department of Horticulture, University of Kentucky, Research and Education Center, P.O. Box 469, Princeton, KY 42445 U.S.A
This publication was originally prepared as the review paper Spigelia marilandica propagation: A Review for the 2003 Eastern Region International Plant Propagator's Society meeting. It was published in the IPPS Combined Proceedings 53:510-512. This publication was revised January 24, 2006
Spigelia mariclandica, Indian Pink, is native to west Kentucky. Infrequent in southern Kentucky (Wharton and Barbour, 1971) it is found as a roadside plant on a variety of soil types. Over it’s range, Florida into east Texas, southeast Oklahoma, southwest Indiana, northwest Georgia, and east South Carolina it is common (Duncan and Duncan, 1999). The red tubular flowers with five folded lobes showing the yellow interior color are stunning; “stop people dead in their tracks” (Armitage 1997). An average of 13 (8-17 on 68 stems on a five year old division) of the 2 inch (5 cm) upright flowers are found on a one-sided cyme. The glossy ovate, opposite, sessile leaves add to the attractive appearance of the plant. West Kentucky plants grow 18-24 inches (46-61 cm) tall in sun or shade landscape environments. The bloom period starts in late May and continues through June, occasionally scattered blooms will occur in the fall. Rick Darke (2002) says they will re-bloom heavily if cut back after June flowering. Individual plants in the University of Kentucky Research and Education Center Botanic Garden, Princeton, KY are now seven years old and show signs of indefinite longevity. Spigelia marilandica is known to attract hummingbirds (Cullina, 2000; Glick, 2002) adding this characteristic to the beauty of the flowers, the size of the plant, it’s environmental and pest tolerances and longevity in the landscape indicate Spigelia mariclandica is an plant that should be more widely used in landscapes, in particular, Kentucky landscapes. A quick search of catalogs and nursery calls indicate the plant is available in limited numbers, but Schmid (2002) states “this dazzling native is still uncommon in gardens and deserves to be more widely grown”. Propagation difficulties have limited availability in the past.
Spigelia mariclandica seed is found in a two-sided capsule. The seeds are grouped into small balls of 4-7 seeds that separate readily. The capsules ripen from July 1 through July 15 in the UKREC Botanic Garden. . Unfortunately, within one or two days the seed will “explosively dehisce” (Darke, 2002) and be lost to the seed collector. The capsule will be black on the top and black-green on the bottom just before this happens; seed capsules collected at this time will split open ejecting the seed into the bag shortly after removal from the plant. Seed collection requires daily observation. It is recommended that seed be sown immediately after collection to ensure high percentage germination (Cullina, 2000; Glick 2002). Two year old seedlings will bloom. Barry Glick (2002) states deer don’t browse Spigelia marilandica but our experience trying to collect seed in the wild would indicate that deer or some other creature does eat the flowers and stem down to the foliage in a similar fashion to deer feeding observed on Trillium recurvatum in west Kentucky.
Building up a group of stock plants that can provide enough seed to produce thousands of plants is possible but such a collection of plants may be better used to propagate Spigelia marilandica by division. We have had very good success propagating by division. Field-grown plants in an irrigated nursery environment produce a dense fibrous root system. The root system density requires cutting the plants apart with a sharp knife or pruners to separate the divisions. Some, but not all, divisions will bloom the first year. Glick (2002) recommends dividing in the spring: the plants are late growing and there is adequate time to spring divide. Plants propagated by division, including Spigelia marilandica, at the UKREC that are to be placed in the landscape or field nursery are divided prior to fall equinox (approximately September 20) to allow time for root development to limit frost heaving damage. Late fall-divided plants (after fall equinox) are containerized and placed; in a white plastic covered quonset structure or under microfoam for overwintering. We also divide Spigelia marilandica in the spring.
J. C. Raulston (1990) stated “---- for a cultivar to be a mass-marketed item, it’s going to have to be propagated by stem cuttings”. Spigelia marilandica can be propagated by stem cuttings (Bir and Barnes, 2000; Cullina 2002; Foster and Kitto, 2000). Tip cuttings should be taken from plants that have not flowered; the taking of cuttings keeps the plants from flowering making it possible to harvest cuttings two or three times before the plants stop growing in the fall. Foster and Kitto (2001) were able to take tip cuttings every 8 weeks from stock plants maintained in a regulated greenhouse environment. They recommend growing on the rooted cuttings in the same environment to improve root development. The American Nurseryman article by Foster and Kitto (2001) contains descriptions of the materials and methods making it possible to reproduce the 91% rooting they reported in a HortScience abstract (2000). Bir and Barnes (2000) Tips for Success When Rooting Spigelia marilandica include: taking 2-3 node tip cuttings from non-flowering stems; apply 2000-3000 ppm IBA liquid; root in a well-drained medium; direct stick in small pots, root and grow in 50% shade; and overwinter in a minimally heated greenhouse. The 2000 ppm IBA liquid treatment was also recommended by Cullina (2000). Perlite based rooting media: 2:1 perlite to spaghnum peat or 4:1 perlite to peat was used in rooting experiments by Bir and Barnes (2000) and Foster and Kitto (2001) respectively.
Dr. Sherry Kitto, (Kitto, 2003) University of Delaware, has developed a tissue culture propagation protocol. AgriStarts III, http://www.agristarts3.com/, Eustis, FL is propagating Spigelia using this protocol and the plants from them have grown well.
Depending on the resources of the propagation nursery; propagation by seed, division, cuttings, tissue culture or a combination of the different propagation methods, should make it possible to meet increased demand for this desirable plant.
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