Terrific tree ferns

Having been on the planet for 450 million years, moss holds the record as the world’s most ancient living plant. At 200 million years old, tree ferns are relative babies but they are still considered prehistoric. They’re awe-inspiring in their natural habitat and can bring a similar shady rainforest vibe to a garden. While their canopies can reach 6m across, the taller they grow, the less space they take up at ground level, and tree ferns can work in a range of spots, from the smallest courtyard to the largest garden.

How to grow tree ferns

There are thought to be 600-700 tree fern species, most of them from the Southern Hemisphere. Many are from tropical areas, but in Australia they also grow naturally in subtropical and temperate rainforests, as well as moist open bushland and gullies. This gives us useful information about their requirements. Like most other ferns, they grow best in light to heavy shade, but early morning sun won’t hurt them. Shady spots in the garden, usually along the south side of the home, are often underused. These shady areas are a perfect place to let your inner pteridomaniac go wild!

The best time to plant is in autumn, late winter or early spring. Choose a space that is protected from strong wind. Tree ferns grow best in loamy soil, which will hold moisture, and require a neutral to slightly acidic pH. If you’re growing them in sandy soil, add coir peat and compost. Plant potted specimens at the same depth as they are in the pot. If growing from a trunk, plant them deep enough to be stable.

Water in well, and ensure your tree fern never dries out in the first year. After that, water once a week, as needed, during dry times from spring to autumn, watering the trunk, too, but not the crown. The trunk is actually a specialised rhizome (think ginger or asparagus). Maintain a good cover of organic mulch to keep soil moist. Feed with a well-rotted animal manure or commercial organic fertiliser in autumn and spring.

Types of tree ferns

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

Planting a semi-mature trunk creates instant visual impact in the garden. With a 50cm diameter, it is one of the widest trunks among tree ferns. This species is found in forests from south-east Queensland to Tasmania and can grow 12–15m tall, but is likely to mature at 4–5m.

The graceful arching fronds, produced in spring and autumn, can reach 3–4m long. The stalks are smooth and covered in fine, reddish-brown hairs, while the leaves are dark green above and a lighter shade underneath.

ROUGH OR HARSH TREE FERN/ WHEKI (Dicksonia squarrosa) A New Zealand native, this plant is much faster-growing than its Aussie relative – with the trunk potentially growing 10–80cm a year – although its fronds are fewer and shorter than those of D. antarctica. Reaching up to 6m tall, it is reasonably wind-tolerant and will grow in full sun if the roots are kept moist. The rough tree fern spreads via rhizomes and can form colonies of trunks.

ROUGH TREE FERN (Alsophila australis syn. Cyathea australis)
Growing up to 20m tall in the wild, the rough tree fern (below, left) is one of the tallest tree ferns. It is found in forests from south-east Queensland to Tasmania and South Australia, and is named for the knobbly bits on its trunk and the short, coarse, densely packed spines at the base of the stipes (stems). The fronds reach 2–5m, creating lovely filtered shade below. A popular choice for gardens, it can withstand sun if the roots are kept moist, and will tolerate salty winds in coastal gardens.

GOLDEN TREE FERN (Dicksonia fibrosa)
Similar to but shorter than the soft tree fern, the golden tree fern (above, right) reaches 4–6m at most. Its fronds are shorter too, and golden. The dead fronds are held on the plant, creating an unusual ‘skirted’ trunk. Indigenous to extremely cold areas of New Zealand, this tree fern also tolerates sun in cool climates.

BLACK TREE FERN (Sphaeropteris medullaris)
This attractive tree fern (below, left) has a characteristic slim, black trunk reaching 20m tall, and arching 5m-long fronds with black stipes. It’s much sought-after but, hailing from New Zealand, Fiji, Tahiti and other islands, might take some hunting down. Fast-growing and cold-hardy, the plant copes with wind and sun exposure if the roots are kept moist.

LACY TREE FERN (Sphaeropteris cooperi syn. Cyathea cooperi)
This tree fern (above, right) is named for its highly divided ‘lacy’ fronds. These reach up to 5m long on a 15cm-diameter trunk that grows to 12m, giving the plant a palm-like appearance. As the fronds age and fall off, they leave distinctive, coin-like spots on the trunk. Native to forest areas from Far North Queensland to south-east coastal New South Wales, the lacy tree fern prefers warmer, frost-free areas. One of the faster-growing and hardier tree ferns.

Header image by Shutterstock