Rosemary scrub is an open sand habitat dominated by Florida Rosemary (Ceratiola ericoides), an aromatic shrub common in Highlands County, Florida. Areas of rosemary scrub are informally referred to as “Rosemary balds” for the patches of exposed white sand between shrubs. These patches of sand are kept open naturally due to a phenomenon known as allelopathy in which Florida Rosemary exudes a chemical through its roots and leaves that prevents certain plants from growing next to it.

Many rare herbaceous plant species found only on the Lake Wales Ridge are adapted to rosemary scrub habitat despite, or perhaps because of, this allelopathy. “These species are able to germinate near Florida Rosemary in open white sand patches in places that other, more common species, cannot” explained Hannah Bowen, a research assistant in the Archbold Plant Ecology Program. Providing habitat for endemic herbaceous species is one of the reasons that rosemary scrub is so special. Yet, rosemary scrub with a history of disturbance from heavy machinery, sometimes lacks important habitat characteristics.

Photo by Dr. Aaron David

“Disturbed rosemary scrub looks all wrong,” says Dr. Aaron David, Director of the Archbold Plant Ecology Program. “The shrubs are spaced too far apart to carry a fire, the open sand is filled with lichens and spike moss, and there isn’t enough Florida Rosemary.” Ultimately, these conditions are not suitable for many of the rare herbaceous species.

The Archbold Plant Ecology Program is working with the United States Fish and Wildlife Service to restore a historically disturbed rosemary scrub patch using mowing and controlled burns to promote the germination of federally endangered plants. Mowing will chop up the shrubs and trees into smaller pieces of debris hopefully ensuring that controlled burning will be more successful, which will hopefully lead to higher establishment of rare herbaceous species.

To test if mowing with a tractor before a controlled burn is worth the trouble, Archbold Land Manager Kevin Main mowed some areas of a disturbed Rosemary bald and left some areas un-mowed. Scientists in the Archbold Plant Ecology Program then seeded several study plots in both the un-mowed and mowed areas with 3 endemic and federally endangered plant species: Wedgeleaf Button Snakeroot (Eryngium cuneifolium), Highlands Scrub Hypericum (Hypericum cumulicola), and Scrub Blazing Star (Liatris ohlingerae). Then, the team burned the experimental unit and has been monitoring the seeded plots. “It can take years to see the long-term effects of land management activities like mowing and burning,” says Bowen.

Photo by H

Archbold scientists also monitor the spread of the invasive Natal Grass, and, so far, have found no increase in invasive species with mowing. “Mowing can sometimes promote the spread of invasive species, but these results suggest that this treatment is not spreading Natal Grass” says David.

This work is particularly important given recent declines in citrus production and increases in housing development. Because rosemary scrub occurs in high elevation areas, the land is desirable for both citrus and housing developments. An understanding of how to restore rosemary scrub for at least a portion of old groves will help protect this rare habitat. “It’s great that we can conduct experiments to understand and promote the most effective restoration practices,” says Bowen. “Through this work, we’ve added thousands of endemic seeds to the seedbank of this rosemary bald, which may germinate in years to come."