Weeds of Wednesday: Smooth Rattlebox

Cypress Bend Community Preserve, Oslo Riverfront Conservation Area, Weed, Weeds of Wednesday

On our visit to Cypress Bend Community Preserve on 5-5-2018, we saw smooth rattlebox (Crotalaria pallida var. obovata), pictured above, growing in the ruderal area of the parking lot. Fifteen species of crotalaria are found in Florida, and this widely distributed species is non-native — likely from Africa. It is most often found growing in sandy soils in disturbed spots like old fields, vacant lots, and roadsides.

In 2008, this plant was growing on the northwestern edge of the parking lot at Oslo Riverfront Conservation Area along with the more stout and substantial showy crotalaria (Crotalaria spectabilis), the taller crotalaria to the right …

The flowers of the larger and showier species are bright and completely yellow. The flowers of smooth rattlebox are marked with reddish-brown striations, some plants more so than others. Streaked rattlepod is another common name for this plant. A beetle, the most primitive of pollinating insects, likely clumsily left a hole in the flower on the bottom left …

Its seed pods, shown below in an unripe state, sport a distinctive upward curve and contain three dozen or more tiny hard seeds …

Its compound leaves are obovate in shape (egg-shaped with narrow end at the leaf base), hence the variety name obovata …

Non-native crotalaria are far more common than the low-growing native species. Smooth crotalaria can grow to be up to 6′ tall.

This herbaceous annual can be identified from its dense, terminal inflorescence of yellow flowers marked with reddish-brown markings, compound trifoliate obovate leaves, and its upwardly curved turgid pods.

Jonathan Dickinson State Park has produced a guide to the 7 native and non-native species found in the Park. Click here to visit this well-done publication that includes an easy-to-use key.