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Tree ferns

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last updated Feb 26, 2014
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Dicksonia antarctica

Tree ferns are slow growing architectural plants with spreading fronds above a thick trunk. They make striking plants for a sheltered, shady garden.

Cultivation notes Back to top

Tree ferns thrive in a sheltered, humid and shaded position, with plenty of room so that the top of the plant can spread without crowding. Fronds on mature specimens may reach 2m (6ft) or more in length. They should be planted in humus-rich, neutral to slightly acid soil.

Extremely slow growing, these desirable plants only increase by about 2.5cm (1in) a year. Therefore, if you want a plant for immediate effect, you should choose a fern with a length of trunk that suits your planting scheme.

If you buy containerised ferns in leaf, plant at the same level as they were in the container.

Frondless lengths of trunk are also available. Soak the base and plant just enough of the trunk to ensure the plant remains stable. After planting frondless tree ferns water every day until the foliage starts to emerge.

To encourage rooting, don’t feed the plant during its first year.

Watering and feeding

The trunk and crown of tree ferns will not tolerate drying out, so water regularly to ensure the trunk remains damp and spray the trunk with water during hot weather (and during dry conditions in winter).

After the first year of planting, apply a liquid feed (diluted as directed by the manufacturer) to the fronds and trunk once a month, from mid-spring to mid-summer, when the plant is in growth. Alternatively, spread controlled-release fertiliser around the base of the plant in spring at the rate recommended by the manufacturer.

Winter protection

Over the past few severe winters, gardens have suffered losses of trees ferns, which are not fully hardy. To protect plants growing outdoors to avoid damage to fronds, put a handful of straw in the crown and fold the fronds in on themselves. Follow the link to our video on overwintering tree ferns.

Container-grown plants in milder areas should be placed in a sheltered position and the container bubble-wrapped. Protect from late October but remove in spring, before new fronds come into growth. More substantial wrapping is needed if you have a more exposed garden. In cold gardens tree ferns are best lifted and brought into a conservatory or greenhouse.

Container Cultivation Back to top

Tree ferns may be grown in containers, outdoors or in a large greenhouse or conservatory in bright, filtered light and moderate humidity, using loam-based ericaceous compost, adding about 20 percent peat-free potting media for additional humus.

Apply a half strength liquid fertiliser (diluted as directed by the manufacturer) once a week during the growing season, or add a controlled-release granular fertiliser at the base of the plant in spring at the rate recommended by the manufacturer.

Propagation Back to top

If they produce them, tree ferns can be propagated from spores found on the underside of their leaves. However, cold temperatures or difficult growing conditions may inhibit spore production.

The easiest way to propagate tree ferns is from offsets. These are young plants that develop from the roots or trunk. Offsets develop slowly, so are best left to mature until they can be easily handled. Then do the following:

  1. Sever the offsets cleanly from the parent trunk or roots
  2. Pot them up in loam-based ericaceous compost , just deep enough so that they sit upright
  3. Water them in and place the pot in a propagator at 15-20°C (59-68°F) in bright but filtered light
  4. Once new growth shows, start to harden them off to outdoor conditions

Cultivar Selection Back to top

There are a number of tree ferns to choose from;

  • Dicksonia antartica AGM (soft tree fern) – frost hardy
  • D. fibrosa AGM (golden tree fern) – frost hardy
  • D. squarrosa AGM (New Zealand tree fern) – frost hardy
  • Cyathea dealbata – half hardy, bluish tinge to fronds
Dicksonia antarctica

Dicksonia antarctica

Problems Back to top

Tree ferns are usually trouble-free, but may be affected by cold weather, woodlice living off decaying organic matter in the stems, and red spider mite, which can be a particular problem for plants kept under cover in glasshouses and conservatories.

Quick facts

Common name Tree fern
Botanical name Various, commonest being Dicksonia and Cyathea
Group Perennial with fibrous, woody trunk
Planting time Spring
Height & spread Up to 6m (20ft) height (but usually much less); 5m (15ft) spread
Aspect North or east, sheltered
Hardiness Half hardy to frost hardy
Difficulty Moderate