Whisk fern, Psilotum nudum, doesn't have true leaves, nor does it have true roots. But it is a true plant, not quite a fern, not quite a vascular plant, more fern in appearance, more vascular in function.
It is native to Florida, found in almost every county from the central part of the state to the Keys. It's also found throughout the Southeast as far north as North Carolina and west to Texas and Arizona. Reports of its presence in New Mexico are unconfirmed. Whisk fern is also found in most tropical and subtropical places around the globe, including Asia, Africa, the Caribbean, Mexico, Central America and South America.
Wisk fern grows in swamps and moist forests. We've seen it growing in wet places such as Green Cay in Boynton Beach, Fern Forest in Broward County and Loxahatchee National Wildlife Refuge, but it also occurs in scrubs. We've seen it growing wild in pots — in our own yard. In fact, it can be a minor pest in greenhouses. It grows on the ground, but mainly as an epiphyte, an air plant that uses a tree or rock or something else as structure.
Whisk fern is a small plant, growing six to 12 inches tall, and with many branches. The stems have green and yellow nodes that are actually the reproductive structures. Green are immature, yellow mature. It does not produce flowers or go to seed. Instead, it spreads via spores, as ferns do. Vascular plants typically have leaves and roots, and tissue that conducts water and nutrients to their various parts just as animals have arteries and veins throughout their bodies that do the same. Most plants we see, trees, grasses, ferns, are vascular.
Non-vascular plants, algae and true moss, lack these tissues and lack true leaves and roots. From the standpoint of evolution, they are seen as primitive, the oldest plant forms. Whisk fern also lacks true leaves and roots, but has vascular tissue that moves water and nutrients throughout the plant. It's similar to the earliest forms of vascular plants but some believe that they represent a separate evolutionary line.
In some places where it's found, whisk fern is used medicinally. Extracts are used to treat infections and diarrhea. It's also used as a laxative. And like many traditional remedies, there is some scientific evidence that supports its use. Researchers have found that whisk fern indeed has some antibacterial and antifungal properties.
Whisk fern is a member of Psilotaceae, a family of plants without true roots and leaves. Whisk fern is probably the most notable member. Other names for whisk fern include skeleton fork fern and moa.