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Distribution: All of Florida west to Mississippi, north to South Carolina. Not threatened.

Habitats: Florida rosemary grows on excessively to well-drained sandy soils in Florida scrub. Florida rosemary is a local structural dominant on mature coastal dunes, also can dominate white sand knolls in scrub on the Lake Wales Ridge and other ancient inland dunes of Florida. It can occur intermixed with scrub oaks on white sand and is occasional in dry scrub on yellow sand, especially in previously disturbed areas. Florida rosemary occurs on coastal dunes in Mississippi, and river dunes and sand ridges of Georgia and South Carolina.

Life History: This species is a much-branched perennial evergreen shrub, eventually growing as tall as 2 meters in height. Large plants are often growing in spherical mound that may be comprised of several indistinguishable individuals. Seedlings have distinctive, symmetrical patterns of leaf insertion in 4’s or 6’s. The leaves are strongly revolute (needle-like) leaves 8-12 mm, opposite to whorled. Florida rosemary has tiny flowers, bronze or yellowish in color, and clustered in leaf axils. The fruit is a two-seeded yellow drupe to 3 mm diameter. Only 20% of biomass is held belowground, and the plants are shallowly rooted. Rosemary-dominated areas inland have variable fire return intervals of 15-100 years. Plants are killed by fire. Postfire recovery occurs with germination of seeds from the soil seedbank. Seedlings appear aboveground during the second year after burning. Individual Florida rosemary plants may be aged by counting nodes on unsuppressed branches.

Phenology: Seedlings may be found throughout the year. Florida rosemary flowers in spring, summer and fall, with fruits most typical late in the year.

Breeding System and Pollination: Florida rosemary is dioecious (separate male and female plants, usually in approximately equal numbers). The flowers are pollinated by wind.

Genetics: Ceratiola is a monotypic genus. Limited genetic research has been conducted using isozymes (64.7% of 17 loci polymorphic, with 2.55 alleles per polymorphic locus with mean gene diversity of 0.141).

Population Dynamics: All plants that are burned will die, but patchy fires that are typical in many habitats may leave patches of surviving plants. Salt-spray and storms can induce mortality in coastal habitats. Seedlings recruit from a persistent seedbank 2 years after fire or other disturbance and then for several years. Longevity in the seed bank appears to be on the order of 2 to 8 years and seeds require scarification (by sand movement, animals or disturbance) to germinate. Populations show slow recovery after fire with slightly increasing local abundance for first 10 years, thereafter relatively stable. Thinning due to resource competition occurs between 10 to 20 years. Plants are sexually mature at 10-15 years, with peak seed production between 20 and 30 years. Stands usually approximate 1:1 sex ratio with a slight bias towards females. Plants may lose productivity and begin partial dieback after 20 years, but some plants can survive in excess of 50 years. Although 50 year old individuals have been found, after age 35 large branches may rest on the ground and successfully root as the rest of the plant dies back, making ageing of older individuals difficult). Uneven-aged inland stands are typically dominated by a single cohort or a few cohorts, whereas coastal populations are all-aged.

Interesting Facts: Florida rosemary is allelopathic, particularly to herbaceous plants endemic to inland ridge systems. The chemical responsible for inhibiting germination, ceratiolin, has been isolated. The slow recovery after fire provides microsites for colonization of these herbs, including many that are endemic and/or endangered. Herb populations continue to find refuge in the persistent gaps between rosemary shrubs until these sandy microsites are altered by colonizing lichen and litter accumulation. Drupes are consumed by birds, which can disperse the viable seeds. Black bear and lesser scaup also may feed on the fruits. Harvester ants and mice eat seeds. Florida rosemary provides nesting sites for northern cardinal, grey catbird, yellow-rumped warbler, Florida scrub-jay (endangered), common yellowthroat, and mourning dove. In hotter parts of the year, dense stands exude a distinctive honey-like odor.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: We collect long term demographic data on postfire cohorts: annual recruitment, growth, mortality, density and age structure postfire. We are currently studying three populations: burned in 1993, monitored since 1996; burned in 1994, monitored since 1997; burned in 1995, monitored since 1999. We have been studying rosemary spatial distribution and its effects on the demography of other species. We also have collected data on size, gender, and spatial distribution of rosemary shrubs at two sites (Gibson and Menges 1994).

Data Availability: No data are available at the present time.

Contact Person: Eric S. Menges.

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