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#20 - White Sweetclover

White Sweetclover (Melilotus albus) blooms in the spring on the dike at the South end of the ELC campus and truly lives up to its name. The compound, trifoliate leaves emit a strong sweet scent in the spring that increases when dried, hence the name (the author can recommend it dried in a book). This showy but weedy and invasive European wildflower can most commonly be found on roadsides, ruderal sites and generally in the proximity to humans. The latter has to do with the plant’s history in North America as an agent to mitigate the effects of human disturbance of the environment.

This fast growing, biannual plant can grow to be 3 feet tall and tolerates a wide range of moisture and light conditions, and readily colonizes bare patches of sandy soil. Like other plants in the Fabaceae, or pea family, it has a symbiotic relationship with an actinorhizal bacteria in the group Frankia that fixes for the plant unusable atmospheric nitrogen (N2) in the soil and converts it into ammonia (NH3), which helps it to outcompete low growing native vegetation. Thus, it can often be found in large colonies that stabilize and improve soil with its extensive root system.

These traits gave Sweetclover a reputation as a useful agent for soil reclamation on old fields and cattle ranches, as well as for river bank stabilization. It was first reported in North America in 1664 and has since been used and cultivated by farmers for soil enrichment, by ranchers for cattle fodder, and by bee keepers as a honey plant for their, also introduced, honey bees (Apis mellifera, see photo), hence its other common name Honey Clover.

Today it can be found in all 50 states, including Hawaii and Alaska. Even on land managed by the Fish and Wildlife Service it was sowed to substitute nesting habitat and shelter for birds in the 1970s; and yet, despite its wide use, farmers were often hesitant to plant it to improve and stabilize the soil because they feared, for good reason, it could interfere with their crops. In fact it can be quite a challenge to eradicate it once it is established. White Sweetclover produces numerous tiny 2mm long seeds that stay viable for a long time (studies show up to 81 years) and readily germinate with some disturbance (including fire) on nutrient poor soil. At the edge of pyrophil (fire adapted) ecosystems like pine flatwoods, scrub, or high pine plant communities, it is often one of the first plants to grow back after a burn due to its deep tap root that allows it to take advantage of the short time when little competition is present above ground.

White Sweetclover is only one in a long list of examples of plants used in an attempt to mitigate the often devastating effects of human disturbance of the natural world in North America by introducing (or intentionally spreading) exotic species into the environment. A lack of native vegetation as food or shelter for wildlife and livestock or as soil stabilizers cannot be sustainably substituted with the introduction of exotic species that in turn disrupt natural plant communities themselves. Instead a proper understanding and restoration of our natural world is required.

If you would like to learn more about Florida, visit the Environmental Learning Center in Vero Beach and join us on a guided kayak excursion through the hidden backwaters of the Indian River Lagoon. Call 772-589-5050.


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