WORDS & PHOTOS GILLIAN VINE
Despite having almost 200 native species from tiny tots to forest beauties, ferns are somewhat overlooked by gardeners, although they are easy-care plants for damp and shady areas.
LEARNING THE LINGO
The fronds of ferns and lycophytes (club mosses) unfold from a koru, one of our most familiar indigenous symbols. Green plants that have no flowers, ferns reproduce from tiny spores that reside in capsules on the underside of adult fronds. When the capsules (sporangia) break open, the spores germinate in damp places. Some need both a male and female to get going, while ferns of the ‘hen and chickens’ type – Asplenium bulbiferum, for example – produce babies (bulbils) on mature fronds, and these drop to the ground and take root.
There are more than 10,500 living species of fern, members of an ancient family dating back millions of years. In New Zealand, fern fossils from the Upper Jurassic age (145–163 million years ago) have been found, many in eastern Southland, and Cretaceous fossils (66–145 million years ago) have been identified in coalfields near Greymouth.
Tree ferns are often referred to as ponga but, strictly speaking, this name applies only to the silver fern (Alsophila tricolor syn. Cyathea dealbata).
They grow very slowly – for example, the rate for ponga and wheki-ponga (Dicksonia fibrosa) is about 5cm a year, says Darren McClenaghan, owner of Cambridge’s Fronds Nursery. That means that a tree fern with a 1m trunk is about 20 years old.
“The bigger they are, obviously the more expensive they are,” Darren explains.
Fronds’ approach to sourcing ferns is a sustainable one. By removing them from privately owned pine forests that are about to be cut over, plants that would otherwise be destroyed are saved.
RIGHT FOR THE SITE
We usually think of ferns as plants of damp, shady places, but some tolerate full sun. All need moisture to survive, though.
Darren points out that, despite needing dampness, ferns do not tolerate wet feet, which is why they will grow on the edges of swamps but not in the actual bogs.
Asked to recommend ferns for the gardener, he says the first step is to determine what your garden environment is like.
“It’s the dry that tends to kill ferns. You can just about grow ferns anywhere as long as they’re kept moist.”
Easy to grow is piupiu or crown fern (Lomaria discolor syn. Blechnum discolor), which is found throughout New Zealand, typically in drier forests. It likes a light, damp but well-drained soil.
Kiokio (Parablechnum novae-zelandiae syn. Blechnum novae-zelandiae) is a hardy fern for almost all environments, as long as it gets adequate moisture.
“You can grow it anywhere in New Zealand,” Darren says.
New growth is a warm coppery colour, especially when it gets more light. The related swamp kiokio, as its name suggests, needs a wetter site, however, and prefers the shade.
For a ground cover, Blechnum penna-marina grows “almost anywhere” in full sun or semi-shaded sites, its creeping rhizomes quickly making a weed-suppressing mat. New fronds have a pinkish touch.
The rasp fern (Blechnum parrisiae syn. Doodia australis, D. media) likes a sunny spot, which intensifies the red of its young growth. Low-growing (60cm), it can be used as a ground cover.
And, if you want a couple of native houseplants, the button fern (Pellaea rotundifolia) and the maidenhair (Adiantum aethiopicum) are hard to beat. Just don’t forget to water them regularly.
Hen and chickens (Asplenium bulbiferum) is an easy fern to propagate – just collect the babies and pot them up.
Growing from spores is much trickier because they are microscopic and it’s easy to overcrowd the babies. Be ruthless with thinning when they germinate to give them space.
First, choose a suitable potting mix. Peat is good, coir is not, and some growers like to include vermiculite to improve moisture retention and aeration.
Next, sterilise the potting mix to avoid harmful bacteria. This can be done by pouring boiling water on the mix or zapping it in a microwave for two minutes. Cover and leave to cool before sowing.
Sow the dust-fine spores thinly, and as evenly as possible, then cover the container with a plastic bag or wrap and place it in a shady place. Spray with sterilised water if the mix looks too dry.
The first signs of life can take weeks or months and are not baby ferns but things called prothalli that – without boring you with too much botany – grow into ferns.
When they crowd their container, carefully take out little clumps and pot on. Separate them when they fill the second container and then plant out individually.
For tree ferns, growing from a spore to a 2.5m adult can take 50–60 years, Darren McClenaghan says. Therefore, it makes more sense for the gardener to buy mature plants. Never take them from the bush.
Various ferns were used medicinally by Māori. Two Asplenium species were used for skin rashes, as was ponga; Blechnum fluviatile was chewed for ‘sore mouths’ (possibly ulcers); the inner tissue of young mamaku (black tree fern) fronds made a wound dressing, as did the scraped roots of piupiu (crown fern).
Roots of bracken (Pteridium esculentum) were roasted and eaten. Consumed before a sea voyage, this was said to prevent seasickness. It is now known that bracken contains cancer-causing substances and should not be eaten. Cattle and horses can be poisoned by eating young fronds.