Distribution: Scrub buckwheat is endemic to central Florida, and is listed as state endangered and federally threatened. It occurs from Ocala National Forest, Marion County, in the north, to the Lake Wales Ridge in Polk and Highlands Counties as far south as the Archbold Biological Station south of Lake Placid.

Habitats: Scrub buckwheat occurs in oak-hickory scrub, turkey oak barrens, and sandhill vegetation, growing on xeric, yellow sands with no or shallow litter cover.

Life History: Scrub buckwheat is a long-lived herbaceous perennial, with basal rosettes, and flowering scapes. It is non-clonal with a deep taproot. Leaves are green or bronze-green above and densely white-wooly beneath. Basal leaves form rosettes (1-6 per plant). The stem is erect, up to 1 meter tall, and terminates in an open panicle. Each branch of the panicle ends in a cup-shaped involucre. Inside each involucre, 15 to 20 flowers form a cluster. The stalk of each flower starts out erect and then relaxes so that the flowers hang down below the involucre. Flowers are small, silvery-green, silky-pubescent, odorless, and inconspicuous. Each flower is 6 to 8 millimeters long and has six linear sepals. This species does not appear to have a long-term persistent seed bank. It resprouts following fire. Flowering is stimulated by fire, but occurs in some plants without fire. Fires benefit scrub buckwheat populations in at least two ways. Reproductive output increases directly as a result of increased flowering. Scrub buckwheat seedling establishment also increases in burned areas due to litter removal. However, our germination experiment did not show increased germination percentages in recently burned areas, and also highlighted the beneficial effects of partial shading. Complete but moderate fires that remove litter yet allow rapid recovery of shrub and grass canopies may offer the best opportunities for post-fire recruitment of scrub buckwheat.

Phenology: Individuals produce flowering stalks mainly during summer (May-July), but scrub buckwheat can flower at various times of year following burns. Seed germination occurs mainly during the summer.

Breeding System and Pollination: Each reproductive scrub buckwheat individual flowers over a period of months, but presents only one or a few flowers at any one time. Flowers have an easily accessible, generous drop of nectar. Flowers are visited by a variety of insects, including solitary digger and twig-nesting wasps (Parancistrocerus spp. and Stenodynerus spp.), flies (Geron spp.), small solitary bees, and occasional social wasps. Visiting wasps learn the location of each plant and use trap-line strategies. The small number of flowers per plant induces them to visit several plants and probably promotes outcrossing. Individual flowers avoid self-pollination: the anthers open and shed their pollen first, then the pistils, which have kept their stigmas tucked into a tuft of hairs at the base of the flower, straighten up and offer their receptive surfaces to incoming insects. An extremely low number of seeds and fruits developed by experimentally bagged flowers (compared to open pollinated flowers) indicates the need of pollinator services to set seed.

 Genetics: We know of no genetic studies on scrub buckwheat.

Population Dynamics: Using demographic data from ten years (1989-1999) including five fires, we constructed projection matrix models of scrub buckwheat populations in unburned habitats, for populations experiencing a burn, and for populations one year after burning. Stochastic model simulations with these matrices predicted that scrub buckwheat population decline is likely in the absence of fire, and that decline is nearly certain given pessimistic assumptions of fertility. If the optimistic estimates of fertility are appropriate, scrub buckwheat populations may be stable or decline only very slowly. Scrub buckwheat populations were more likely to decline or go extinct as fires become less frequent. Prescribed fire is likely to be the most efficient and effective tool for enhancing scrub buckwheat populations over large areas. Based on currently available data, we suggest minimum fire return intervals of five to twenty years (assuming pessimistic or optimistic fertility estimates). If partial burns are desired or inevitable, more frequent burning will be necessary.

Interesting Facts: Although some scrub buckwheat plants can be killed by intense fires, this species has a high (>90%) resprouting rate. Flowering is also stimulated by fire, a response that seems to be due chiefly to the removal of aboveground tissues.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: We have been monitoring six scrub buckwheat populations in four burn units at Archbold Biological Station (1989-2002). Within each population, we established between four and fourteen permanent 10m x 10m plots. One additional population has been monitored in circular permanent quadrats (3 m radius) at the Lake Wales National Wildlife Refuge (Carter Creek tract) since 2001. These populations occur in areas characterized as the turkey oak phase or the hickory phase of southern ridge sandhill. We marked all scrub buckwheat plants within each plot with flags and numbered metal tags and censused them annually. At each annual census, we monitored all plants for survival, total basal diameter (summed across all rosettes), number of flowering scapes, and number of involucres.

Data Availability: Projection matrices after Satterthwaite et al. (2002).

Contact Persons: Eric S. Menges,  Mark Deyrup.

 References:

1. Carrington, M.E. 1996. Post-fire recruitment in Florida sand pine scrub in comparison with California chaparral. Ph.D. dissertation. University of Florida, Gainesville, FL. 201 pp.
2. Carrington, M.E. 1997. Soil seed bank structure and composition in Florida sand pine scrub. American Midland Naturalist 137:39-47.
3. Carrington, M.E. 1999. Post-fire seedling establishment in Florida sand pine scrub. Journal of Vegetation Science 10:403-412.
4. Deyrup, M. 1997. Learning the language of insects and flowers. Wings 20: 12-15.
5. McConnell, K. and E. S. Menges. 2002, Effects of fire and treatments that mimic fire on the Florida Endemic Scrub Buckwheat Nutt. Eroigonum longifolium var. gnaphalifolium Gandog.). Natural Areas Journal 22: 194-202.
6. Satterthwaite, W., E.S. Menges, and P.F. Quintana-Ascencio. In press. Assessing population viability of Eriogonum longifolium var. gnaphalifolium in relation to fire using multiple matrix modeling techniques. Ecological Applications
7. U.S. Fish and Wildlife Service. 1993. Endangered and threatened wildlife and plants; endangered or threatened status for seven central Florida plants. Federal Register 58(79):25746-25755.
8. Ward, D.B. 1979. Scrub Buckwheat. pp. 86,87 in Rare and endangered biota of Florida, Vol. 5, Plants. Univ. Presses of FL, Gainesville.
9. Wunderlin, R. 1982. Guide to the vascular plants of central Florida. Univ. Presses of FL, Gainesville. 472 pp.

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