Relatives of ferns and horsetails (all Polypodiophyta), and club mosses (Lycopodiophyta) to a lesser degree, Whisk Ferns are peculiar tropical plants that do not produce leaves, root, cones, or flowers. They are simply, Y-branching vascular seedless plants that can be terrestrial or epiphytic.
Psilotum nudum (Whisk Fern, Moa)
Subspecies: roughly 100 cultivars have been produced
Native: tropical regions (including Hawaii)
Hardiness Zones: 8-11
Height: to 50 centimeters
Diameter: aerial shoots to 4 mm in diameter, spreads 30 centimeters in diameter at maturity
Root System: rhizomatous, no roots
Growth Rate: fast (considered weedy)
Age: perennial (persist for longer than 5 years)
Monoecious/dioecious: bisexual, homosporous (monoecious)
Tolerates: most pests (rarely bothered by them), dry soil
Problems (major): none
Problems (minor): weedy in greenhouses, rather poor salt tolerance
Soil requirements: prefers moist conditions, survives in some dry regions, pH 5.6-7.5 (weakly acidic), requires good drainage
Air requirements: requires high humidity and warmth ( keep above 13 C or 60 F)
Watering requirement: moderate
Sun requirement: full sun to partial shades
Vascular tissue: present
Shoot: green stem with stomates (gas exchange), protostele (similar to pith) in cener of vascular tissue surrounded by endodermis
Roots: absent, rhizome present
Dominant generation: sporophyte
Gametophyte: saprophytic (absorbs nutrients from soil), heart or pill shaped, to 2 mm long
Sporophyte: medium green
Strobili: lateral, yellow clusters of synagria (three fused sporangia) interspersed on upper portion of foliage atop enations (leaf-like non-vascular structures supporting the synagria), produce spores
Thallus body: absent
Gemmae cups: absent
Epiphyte: yes (grows in soil, however)
These have vascular tissue but lack leaves, roots, and any seeds. Despite this, they are affected by few pests and do very well for themselves.
These are commonly grown at universities for their unique physiological structures and taxonomic placement.
Mature syrangia and Y-shape at the Plant Biology greenhouse at Southern Illinois University Carbondale
Foliage and enations holding up developing syrangia
All of the images provided were taken by me. They may be used for educational/informational purposes only, provided that this article/online journal is appropriately cited first.