Java fern (Microsorum pteropus): grower data and the name change

What the grower data says

Tropica rates Java fern easy, with low light and CO2 demand and slow growth, and calls it a hardy plant that grows in all conditions ^[1]. Its height rating, 15–30 cm or more after two months, makes it one of the taller undemanding plants; Tropica’s description gives 15–30 cm. Aquasabi profiles the narrow-leaved form rather than the type, with the same easy, slow, low-light ratings, no need for added CO2, a care height of 10–30 cm and water hardness up to “medium” ^[2].

Low light and CO2 ratings mean the fern fits tanks without CO2 injection; Tropica’s fertilizer guide says that plants it rates easy do not need added CO2 ^[3].

Placement and planting

Tropica’s planting advice is the same as for other rhizome plants: grow it on a root or stone, held with fishing line until it has gained a hold, and if it is planted in the substrate do not cover the rhizome, because it will rot ^[1]. Aquasabi lists the narrow form for the middle ground, background and nano tanks, and as an epiphyte ^[2]. Tropica’s fertilizer guide notes that plants grown on rocks and roots can only be fed through the water, because their roots are not in the substrate ^[3].

Growth and propagation

Two forms of propagation are visible in the aquarium.

• Rhizome division. Tropica describes Java fern as easy to propagate by splitting the horizontal rhizome ^[1].
• Spores. The black spots on the underside of the leaves are sporangia, the fern’s reproductive organs. Tropica points out that many people mistake them for disease ^[1]. Aquasabi also sells a form described as the fern’s prothallium, the small first stage that grows from a spore, for use as a low epiphyte of 1–3 cm ^[5].

Several cultivated forms exist; Tropica’s catalog lists ‘Narrow’, ‘Trident’ and ‘Windeløv’ alongside the species ^[4].

Names and taxonomy

The name on most labels, Microsorum pteropus (Blume) Copel., is a synonym in the World Checklist of Vascular Plants. WCVP accepts Leptochilus pteropus (Blume) Fraser-Jenk. in the fern family Polypodiaceae, and lists Microsorum pteropus, Colysis pteropus, Polypodium pteropus and three other combinations as synonyms ^[6]. Between them, the accepted name and its synonyms place the epithet pteropus in seven genera since Blume first described the plant as Polypodium pteropus.

WCVP’s native range for the species is wide: from India, the eastern Himalaya, Bangladesh and southern China through Indochina to Malaysia, Java, Borneo and the Lesser Sunda Islands, 24 regions in all ^{[6, 7]}. Tropica’s grower data simply gives “Asia” ^[1], which agrees.