Have you been out and about in the past couple of weeks and had a beautiful white fluffy shrub catch your eye? If so, you were very likely looking at a fringe tree (Chionanthus sp.) (Oleaceae) in flower.
In Florida, we have two native species of fringe trees. If seen around your neighborhood or perhaps in the main gardens at Bok Tower Gardens you were looking at the more common species, white fringe tree (C. virginicus) which occurs in wooded hammock habitat. However, if you were driving by some xeric natural area in central Florida, you may have been looking at the federally endangered and Florida endemic pygmy fringe tree (C. pygmaeus). Other than the habitat type, the two are difficult to differentiate even to seasoned botanists.
The pygmy fringe tree occurs in scrub habitat in deep sandy soil, with very little shade from the sun and even less access to moisture. The habitat is extremely xeric, and after hot and dry days like those this month, it’s impressive that this species can muster together the resources needed to flower. Scrub species have different adaptations to deal with the low availability of water. Some sow deep tap roots to extract moisture from the water table, and other species have very shallow roots to capture moisture at the soil surface before it quickly percolates through the sand. The pygmy fringe tree has the latter.
The shallow roots can act opportunistically at the soil surface to capture rainfall at soil surface. However, more interestingly, in the evening as the humid air cools and the ambient moisture condenses, water collects on leaf surfaces and drips onto the soil becoming available for uptake by the surrounding vegetation.
You surely have witnessed this phenomenon if you live in Florida and park your car outside overnight during the summer and find your car covered in moisture in the morning. Same thing. It does cause one to admire the ability of our natural world to adapt, survive and thrive in more adverse conditions.
Blog was written by Whitney Costner, Conservation Biologist with the Rare Plant Conservation Program at Bok Tower Gardens.