Rumohra adiantiformis
By Geoff Nichols | Sat, 01 July 2017


House and home improvement gardening

Rumohra adiantiformis; Seven-week Fern, Seven Weeks Fern, Leather Fern, Leather Leaf, Knysna Fern; Seweweeksvaring (Afrikaans)

This is another of our plants that has, over the last couple of decades, been exported and displayed as filler plant material for flower arrangements all over the world, although that is not to say that florists here do not use it. My late father began using this plant, at the request of one of the local Port Shepstone florists, from a clump of this fern that I had collected years before near Oribi Gorge. The plant had expanded into a section of fern “plantation” of about 50 square metres. One day when the florist came to collect orchid blooms to use in wedding corsages, she saw the patch and asked if Dad would supply the shop with fronds. This little operation is still functioning today and helps to pay the rates on the property each year.
This fern is most common in the temperate forests of the southern and eastern Cape province but extends all the way up the east coast into tropical Africa, and is found in many tropical islands off the coast of Africa and across into Australia, New Zealand, Polynesia and even in South and North America.
It wants dappled shade and will tolerate a bit of early morning sunlight. It likes to grow in leaf litter-rich soil, just as it would find itself in a forest. These ferns want plenty of water during the growing season and need to be kept humid in the winter. The ones in my garden expand to the shade line of the trees under which they grow, but they do not venture out beyond this line because the sun scorches the new fronds that develop on the creeping rhizome or stem.
I fertilise my plants with a general mixed fertiliser twice a year - in early spring and in mid-summer. Then in winter, when the plants are resting, they get a good layer of compost that is really leaf mould from the rotted leaves of our Avocado Pear trees. This helps to ensure the mat of fibrous fern roots are kept damp throughout the year. In the new season, if you dig carefully into this layer of mulch, you’ll find the fern roots, with the attendant fungal hyphae (fungal “roots” collectively known as mycelia), growing in this mulch. This fungal association with plants is a whole science in itself.
When propagating this plant, it is simplest to cut off a piece of the creeping rhizome with its roots and a length that has three fronds. Lay this on newly prepared humus-rich soil in a shady spot. Water well, and in about a month to six weeks, the rhizome will begin growing once more by sending out a new frond. The other method for specialist growers is by spore, when you’ll get thousands of plants in a fairly short space of time. From spore to a reasonable-sized plant takes about three growing seasons. 
For me this is a great, stable, long-lived groundcover for tropical and inland gardens that are sheltered from frost. This plant will take some cold, but remember it normally lives in forests where it would not get frost. It is a great garden plant for shady areas, as an under-storey planting along streams, and even next to ponds where there is plenty of moisture. It makes a good container plant.
I have a pair of Bleating Warblers that breed in the most sheltered of my patches - they hide their nest each breeding season by literally sewing the fronds tightly together.

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