Psilotum nudum is genuinely ancient. It lacks roots, lacks true leaves, and produces no flowers — the species name means naked in Latin, and the plant wears that description without apology. What it does produce are erect, bright green, triangular-branching stems that rise to about 20 inches, studded with small yellow sporangia. Found across the tropical and subtropical world, it grows either terrestrial in humusy soil or epiphytic on another plant, in which case it becomes pendulous and decorative without drawing a drop of nutrition from its host.

For the gardener with curiosity and the right climate (Zones 8-10), whisk fern is a conversation piece unlike almost any other plant. Grow it in full sun to partial shade in moist, humus-rich, well-drained soil. It spreads quietly by rhizome rather than true roots and has naturalized so readily in the nursery trade that it occasionally appears uninvited in greenhouse pots — a small testament to its ancient persistence.