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Growing Tree Ferns

25/06/21 Tates Plant Guides

In old, well-grown specimens, the wide-spreading crown of fronds may be seen to rise at a distance, above the ground from a thick stem. Dryopteris filix-mas (Common Male Fern) is the most common example. Higher and thicker trunks are occasionally presented by Osmunda regalis (Royal Fern), growing up to 75cm height. Some tropical members and allies of these genera are more tree-like, e.g. Todea. Pteris also has some sub-arboreal forms. Oleandra is branched and shrub-like, while Angiopteris and Marattia may also rise to 75cm or more. But the tree ferns proper are included in the family Cyatheaceae.

This includes 7 genera: Cyathea, Alsophila, Hemitelia, Dicksonia, Tizyrsopteris, Cibotium and Balantium. A few are herbaceous, but the majority arboreal and palmlike, frequently reaching a height of 15m+. Alsophila excelsa can grow to 25m. Its fronds may reach 7m in length. The stem may branch into many crowns.

DICKSONIA VARIETIES

Dicksonia antarctica: can grow to 15m in height, but usually 4.5-5m. The large, dark green, rough fronds spread in a canopy of 2-6m in diameter. One of the hardiest tree ferns. Will tolerate a fair degree of sun exposure but dislikes strong winds. A sheltered spot in semi-shade is optimal, for maximum growth the trunk should be watered daily in dry weather. Hardy to -10°C but winter protection of trunk is recommended.
Dicksonia fibrosa: an attractive tree fern with a large, spreading crown of dark green fronds and a soft, fibrous trunk. 3m height with fronds up to 2.5m. Easily grown and adaptable, likes cool, moist conditions out of strong winds, and a moisture-retentive soil. Tolerates temperatures below -6°C. Protect trunk in winter.
Dicksonia squarrosa: a slender black trunk covered in yellowish-brown hairs, grows up to 3m. The rough fronds are dark green on top and paler underneath, forming a graceful spreading crown. When mature it can regrow from lower down the trunk if the crown is killed. May be damaged at temperatures below -5°C. Ideal for the shady greenhouse or conservatory, or in tubs in a rich, moist compost.

PLANT CARE

Older ‘recycled’ tree ferns have proved hardier than young plants. Nevertheless, protect young fronds from frost with a handful of straw or bracken placed in the top of the stem. Avoid alkaline conditions, strong sunlight, windy exposed positions or draughty corners.

The delicate fronds are designed to flourish in humid conditions, so special attention must be paid to moisture levels all year round. In hot, dry periods, soak the root ball and spray the foliage and fibrous trunk regularly. Throughout the rest of the year, ensure the fern is watered thoroughly through the centre of the stem, as they absorb moisture through the stem more readily this way. Small-leaved deciduous trees provide the perfect protection and setting: the lightly dappled shade they offer is ideal for tree ferns. Shade cast by buildings often causes draughts.

WINTER PROTECTION

The hardiest of tree ferns just need some straw in the crown of the trunk: this will keep heavy frosts off the fronds that will emerge the following spring. The trunks of half-hardy species should be wrapped in the winter, as should smaller specimens planted in colder regions.

POSITION

Tree ferns like shade or semi-shade, and shelter from the wind, as they grow as understory plants in temperate forests in their native habitats.

SOIL MIX

Plant in a slightly acid soil – ericaceous compost is highly recommended. For tree ferns the trunk must be planted deep enough for the fern to stand upright under its own weight. The taller the trunk, the deeper it should be planted.

WATERING

Tree ferns like their trunks to be completely soaked at least twice a week in warmer months. If left outside no supplementary watering is needed during late autumn/winter.

FEEDING

Liquid feed in the spring as the fronds begin to emerge, and feed throughout the warmer months. Tree ferns are greedy feeders. However, they dislike high levels of nitrogen. Use an organic mulch of leaf mould, chopped bracken or garden compost, spread thickly on the ground surrounding the stems.

PLANTING FERNS

Most species of fern need friable, well-drained soil. Mulching will improve the drainage and condition of the soil over time. If there is a clay pan, condition the soil to break up the clay and prevent waterlogging. If the soil is light and friable, make a hole slightly larger than the fern container and add a little compost to the bottom of the hole. If the soil is heavy or clay, the hole will need to be twice as big as the fern container. Line the hole with compost and small stones to improve the drainage and condition of the soil around the plant. Once the fern has been placed, mix the soil with compost and fill the hole. If the soil is particularly heavy, it is advisable to dig small channels radiating out from the hole to drain the soil. Once planted, sprinkle a small top dressing of fish, blood & bone to help establish the fern. Do not plant too deeply – make sure the crown is not covered or the fern could develop crown rot.

Growing Tree Ferns

DICKSONIA VARIETIES

PLANT CARE

WINTER PROTECTION

POSITION

SOIL MIX

WATERING

FEEDING

PLANTING FERNS

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