The new donation of Lecanopteris ferns to Botanische tuin Zuidas

A few months ago I visited Botanische tuin Zuidas, a small botanical garden between the tall apartment buildings of south Amsterdam’s business centre. The Botanic tuin Zuidas houses a very rich plant collection with more than 6,000 species. Through the 40 years of its existence the Botanic garden has built up a large collection of plants, trees and shrubs with natural-historical value. It is open to the public throughout the year, without entrance fee. They maintain a small outdoor fern garden with some oddly

growing Dicksonia in containers. I discovered, not long ago , that they have acquired a collection of five Lecanopteris ferns. These ferns were grown and donated by Luuk Jaarsma.

Lecanopteris is a genus of ferns that symbioses with ants. Traditionally ferns of this genus were referred to as ‘Ant Ferns’—although more recent taxonomic discoveries have lumped other species such as Phymatosorus diversifolius into this genus which are not typically referred to as Ant Ferns. They are found from Southeast Asia to New Guinea. The genus was described by the Dutch scientist Elbert Hennipman (1937–2014) who had a large collection at the Utrecht Botanical Garden. Luuk Jaarsma made beautiful drawings for the Dutch Fern Society.

They are growing in a soil mix described for the Dutch Fern Society by Jaarsma (2015). This is a mixture of one part sphagnum, three parts Anthurium or Fern compost (open and low in nutrition) and two parts orchid compost (orchid bark plus added Osmocote fertiliser). Jaarsma also mentioned that they can tolerate a lot of light and don’t really need very tropical temperatures. They are elevated using upturned pots to avoid being eaten by mice, which is a problem in the greenhouse at Botanische tuin Zuidas. The mice are fond of the fresh, young green fronds.

In the Netherlands, there are three other gardens that have Lecanopteris in their collections: Hortus botanicus Leiden, Botanische Tuinen Utretcht and Hortus Botanicus Amsterdam. You can find the species in the ‘Garden Explorer’ of those gardens.

hortusleiden.gardenexplorer.org

dehortus.gardenexplorer.org

utrecht.gardenexplorer.org

The ‘Ant Fern’ genus originally contained around 13 species, but Perrie & Brownsey recently increased to around 25 taxa in 2021. Here’s a key based on Hovenkamp’s work from 1998—useful if you ever find yourself in Amsterdam!

1a. Rhizome covered with peltate scales

→ 2

1b. Rhizome not covered with peltate scales

→ 5

2a. Rhizome massive, strongly flattened, arched, scales sparse, not completely covering the surface L. mirabilis

2b. Rhizome hollow, thick, scales dense, covering the surface

→ 3

3a. Fronds simple, rhizome little-branched L. sinuosa

3b. Fronds pinnatifid, rhizome frequently branched

→ 4

4a. Rhizome a uniform structure, all branches hollow, scales mostly with a brown centre L. crustacea

4b. Rhizome consisting of solid, frond-bearing main branches and hollow, ovate or irregularly shaped, frondless lateral branches, the scales mostly with a blackish centre

L. lomarioides

5a. Rhizome and fronds glaucous, naked L. deparioides

5b. Rhizome green, with spines, coralloid outgrowths or dense glandular indumentum (lens!), or stipe and rachis with hairs below

→ 6

6a. Rhizome with spines or coralloid outgrowths in two rows, replacing fronds; a single internal gallery system; and hollow, protruding phyllopods

→ 7

6b. Rhizome with irregular, dense cover of spines or coralloid outgrowths

not re-placing fronds; two internal gallery systems; and solid phyllopods

→ 11

7a. Rhizome with hollow spines; fronds entire to pinnatifid L. balgooyi

7b. Rhizome with solid spines or coralloid outgrowths; fronds pinnatifid → 8

8a. Rhizome with coralloid outgrowths 1–3 cm long L. carnosa

b. Rhizome with spines → 9

9a. Large plants; rhizome 2.5–3.5 cm thick, with abundant spines; fronds up to 1 m long L. celebica

9b. Smaller plants; rhizome to 2.5 cm thick, with few spines; fronds up to 45 cm

→ 10

10a. Rhizome covered with shorthairs and scattered scales, stipe and rachis glabrous, sori round L. pumila

10b. Rhizome glabrous except near apex, stipe and rachis with persistent hairs below, sori laterally flattened L. luzonensis

11. Fronds simple, sori deeply immersed on lamina L. spinosa

Here are short descriptions of the Botanische tuin Zuidas Lecanopteris collection.

L. balgooyi

The rhizomes are covered with very few scales. They have spines over their rhizomes. The spores grow underneath the frond. The fronds are entire pinnatifid with a length between 25–45 cm.

L. carnosa

The rhizomes turn black/dark blue. The spores grow on the edges of the fronds. The leaves have deeply pinnatifid (pinnately divided but not all the way to the central axis) with a length between 25–90 cm.

L. deparioides (syn. L. curtisii)

The rhizomes covered in blue green waxy layer with no scales. The spores grow on the edges of the fronds. The fronds are monomorphic and deeply pinnatifid. Length between 30–70 cm.

L. celebica

The young rhizome is green and later more brownish. The spores grow on the edges of the frond. The fronds are monomorphic, deeply pinnatifid. The leaves get a length 30–85 cm.

L. pumila

The rhizome is covered with short hairs and scattered scales. The young rhizome is green and later more brownish. The spores grow on the edges of the frond. The fronds are monomorphic, deeply pinnatifid. The fronds get to a length 20–40 cm.

MIGUEL FERNANDEZ VOORTMAN

Miguel is a Dutch horticulture graduate based at the Hortus Botanicus in Leiden, where he has worked on a voluntary basis since his early teens before being appointed full time. He is particularly interested in ferns and has worked alongside Harry Roskam in maintaining and expanding their large hardy fern collection. Prior to his appointment at Leiden, he worked at Henk Braam, one of the biggest companies in the world specialising in the mass- production of fern sporelings for the horticulture trade. He is a regular attendee at IATFG meetings and has contributed to a previous BPS newsletter.