Tree ferns

Prehistoric tree ferns have it made in the shade, adding mega drama and a ‘lost world’ feel to the garden, writes

Tree ferns are among the world’s most ancient plants, having survived Queensland’s own Jurassic dinosaur, Rhoetosaurus brownei, nibbling their fronds about

165 million years ago. Awe-inspiring in the wild, they add drama and rainforest appeal when planted in the garden. Used strategically, tree ferns can become the stars of the show in the largest garden or the tiniest courtyard. Their spectacular sculptural habit is set off by low-growing plants that have similar care requirements.

Getting started

Tree ferns grow mostly in the Southern Hemisphere and are often associated with the tropics. In Australia, they also grow naturally in subtropical and temperate rainforests, as well as moist, open bushland and fern gullies. They do well in light to heavy shade, although most will cope with early-morning sun. Many of us have shady, underused spots in the garden, often on the south side of the property, and these areas are perfect for letting your inner pteridomaniac go wild!

The best time to plant tree ferns is autumn, late winter and spring. Choose a position out of strong wind. They’re adaptable to different soil types, as long as it holds moisture and has a neutral to slightly acidic pH. Add organic matter to the planting hole to help retain moisture. Plant potted specimens to the same depth as they are in the pot. If growing them from a trunk (see Dicksonia species, below), plant them deep enough so they are stable.

Water the plant in well, and ensure it never dries out for the first 12 months. After that, water once a week, as needed, during dry times from spring to autumn, applying water to the trunk, too, but not the crown. Maintain a good cover of organic mulch to keep the soil moist. Feed with well-rotted animal manures or commercial organic fertilisers in autumn and spring.

Dicksonia species

Although it’s one of the slowest-growing species (2.5cm per year), the soft tree fern (Dicksonia antarctica) is arguably the most commonly grown because of its resilience once established. It can be purchased in a pot or as a sawn trunk (with or without fronds). It’s one of the few tree ferns worldwide that grows new roots from the base of a cut-off trunk, but the part left in the ground will not reshoot.

Planting a semi-mature trunk creates instant visual impact in the garden. With a 50cm diameter, it’s one of the widest

trunks among tree ferns. Found naturally in forests from south-east Queensland to Tasmania, this species can grow 12–15m tall, but is more likely to mature at 4–5m. The graceful arching fronds produced in spring and autumn can extend 3–4m long. The stalks are smooth and covered in fine, reddish-brown hairs, while the leaves are dark green above and lighter underneath.

A shorter version is the golden tree fern (D. fibrosa), which is similar but reaches a height of only 4–6m at most. Its fronds are shorter, too, and golden in appearance. Dead fronds are held on the plant, creating an unusual ‘skirted’ trunk. Indigenous to extremely cold areas of New Zealand, it also tolerates sun in cool climates.

Another New Zealand native is wheki

(D. squarrosa), also known as the rough tree fern or harsh tree fern. It is much faster-growing than its Australian relative, potentially putting on 10–80cm of trunk a year, albeit with fewer and shorter fronds,

and can reach up to 6m tall. It spreads via rhizomes and can form colonies of trunks. It is somewhat wind tolerant and will grow in full sun if the roots are kept moist.

Cyathea species

Growing to 20m in the wild, another rough tree fern (Cyathea australis) is one of the tallest tree ferns. Occurring in forests from south-east Queensland to Tasmania, it is named for the knobbly bits on its trunk and the short, coarse, densely packed spines at the base of the stems (stipes). It’s a fast-growing species with fronds that grow 2–5m, creating lovely filtered shade below. Rough tree fern is a popular choice for gardens because it can withstand the sun if its roots remain moist, and it will tolerate salty winds in coastal gardens.

Lacy tree fern (C. cooperi) is so-named for its largely divided ‘lacy’ fronds. These reach up to 5m long on a 15cm-diameter trunk that grows up to 12m tall, giving the

CLOCKWISE FROM LEFT

Soft tree fern (Dicksonia antarctica) has one of the widest trunks among tree ferns; harsh tree fern (D. squarrosa) spreads by rhizomes, with multiple plants forming a lovely shady arbor; a golden tree fern (D. brosa) with a new ush of distinctive ‘gold’ fronds.

plant an elegant, palm-like appearance. It also has distinctive coin-like spots left where old fronds have broken away from the trunk. Found in forests from Far North Queensland to south-east coastal New South Wales and south-west Western Australia, it prefers warmer, frost-free areas, where it grows quickly.

With its characteristic slim black trunk reaching 20m tall, and 5m-long arching fronds with black stipes, the black tree fern (C. medullaris) is much sought after. Hailing from New Zealand, Fiji, Tahiti and other Pacific islands, it may take a bit of hunting down. It is fast-growing and cold-hardy and copes with wind and sun exposure if the roots are kept moist.