Tree fern: everything you need to know to grow a tree fern

By Daisy Bowie-Sell

Published: Wednesday, 18 January 2023 at 12:00 am

Our favourite tree fern, Dicksonia antarctica comes from south-east Australia. They’re evergreen and raise themselves up on thick, fluffy, textual trunks, sometimes to 15ft or more after many years. Their canopy of delicately feathered symmetrical fronds can grow to 12ft across. No wonder then, that they’re called tree ferns. The view from above is unsurpassable. The face that plants show to the sun is often their finest face. In the case of tree ferns, this is undoubtedly true. This is why they are perfect for planting in areas where you can look down on them. For the adventurous, why not build a raised walkway to view them from above? In addition to this, planting them in a grove as part of a woodland walk way can create an enclosed area of dappled shade, ideal for a vast array of underplanting.

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Spectacular tree fern from the forests of eastern Australia with impressively large fronds. Thrives in a moist, semi-shade environment. Looks best planted with complementary woodland plants. 4m. AGM*. RHS H3, USDA 9a-10b.
© Jason Ingram

Interestingly, the shorter, younger Dicksonia antarctica tend to come from areas where trees such as Eucalyptus are grown for commercial benefit. Once an area is cleared of both tree fern and Eucalyptus the ground is burnt and the pioneer species are the first to grow through. The taller specimens are harvested from areas of hardwood production.

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Everything you need to know about tree ferns

A tree fern trunk

The trunk of a tree fern is all root, so it’s possible to cut one down with a chainsaw, remove all the fronds, put it in a refrigerated and decontaminated container, send it halfway around the world, bung it in a pot and let it start a new life. The idea that this can be done with utter impunity is untrue, though. It will certainly notice but, given time and the right spot, it will regain its former majesty. Once planted and the base of the trunk comes into contact with moist compost, it is stimulated to produce new roots. It’ll often take 12 months to fill a standard pot with roots.

How long do tree fern fronds take to unfurl?

The taller the tree fern, the longer it takes for the fronds to unfurl following their journey. At first, the new fronds emerge looking a bit like the knuckle of a clenched index finger of an orangutan. Within six weeks they can be fully unfurled with an arching span of 6 to 8ft – very dramatic.

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A tree fern in a small urban garden

How fast does a tree fern grow?

The rate of growth varies enormously, according to microclimate and soil conditions. An okay Dicksonia will produce a new rosette of fronds in the spring and then stop growing until the following spring. A happy Dicksonia will do the same, but then just carry on chucking out new fronds at an extraordinary rate. They grow in profusion in well protected coastal gardens from west Dorset, around the Cornish peninsula and all the way to north west Scotland. Also, in central London they’ve become common place, with the South East of England following close behind.

How to plant a tree fern

Given the cost of tree ferns, the challenge is to have as much of the plant out of the ground as possible. So, when it comes to planting, it’s a question of stability. For the large ones, you can drill a hole into the centre of the trunk (yes, literally drill a hole) and insert a metal rebar to act as an anchor in the ground. You can also wire to guy them to the ground. For smaller trunks, digging a small hole to bury them in works well and the depth of that is dependent on how densely you compact the soil around them. If you have a new house and a new garden (especially in an area where clay predominates) grow them either in a pot or wait for a few years. Ferns are fuss pots and will only grow in good friable, well-drained soil with lots of organic content.

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© Jason Ingram

How to grow and care for a tree fern

How to wrap a tree fern in winter

Much is spoken on the hardiness of these plants since their importation from Australia in the mid-1990s. This is a plant whose geographical distribution reaches from central Tasmania to southern Queensland. After a very cold winter, it would appear that this hardiness varies from plant to plant, but there’s absolutely no way of anticipating which ones are hardy and which ones are not until it’s too late. So, if your garden gets cold, wrap your tree fern up in the winter. The most important thing is to protect the crown. Wrap the crown in fleece (you can add straw as well) to protect the future development of emerging new spring fronds. We never think there’s much point tying up and fleecing the fronds as they always look so tatty when you unwrap them. We prefer to leave the unfurled fronds for additional winter theatre (you never know – it might snow). Frost damaged fronds can be snipped off in early March to make way for lovely new emerging knuckles and unfurling fronds. Short of a catastrophic winter you will be delighted to see hints of a new crown of fronds emerging when you remove the winter protection. If you have the means to build a stack of straw bales around each plant this also works well.

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A tree fern in a small urban garden
© Jason Ingram

How often to water tree ferns

We would suggest you use an irrigation system and make sure the dripper stake is stuck securely into the crown. If using the garden hose also water directly into the crown, dampening the trunk as well, remember this is part of the root system. When it’s hot, daily watering is required whether through an automatic system or manually with a hose. The key is to regularly look at your tree fern and assess their condition, gently rock the trunk slightly, it should feel sturdy but not too heavy. A dry, flaky and hollow sounding trunk or wilting and drying fronds can indicate stress from too little water. Too much water leads to rotting crowns. Feel the soil and trunk – the ground should not feel dry and pale or too dark and sodden. As you approach the winter you should turn off your irrigation system. As with all plants, the trick is to remain balanced and avoid any sudden dramatic changes to plant care – often human intervention is the biggest killer of plants.

Where to plant tree ferns

Ideally, any tree fern with a trunk over 2 foot should be planted in the ground but they can grow in a pot as long as they are well stabilised. They like a bit of shade (but not too much; they get thin and drawn), nice organic soil (which all ferns like) and humidity. People are often surprised that tree ferns grow happily in Los Angeles where it hardly ever rains. The answer is the Pacific Ocean. It might not rain much, but the ocean makes coastal areas humid enough to keep tree ferns happy. They also like space to show off their symmetrical loveliness.

When new fronds are emerging (this goes for Cycads and one or two other plants) and they’re in a pot, don’t move the pot. The plant’s internal command centre is organising its fronds in a way to gain the maximum light. To us, the result is beautiful symmetry. Move the plants while the fronds are unfurling and as far as it’s concerned, the sun’s changed position and the fronds will twist – resulting in a hopeless mess. Once all of the fronds are out and settled down, then you can move the plant if you need to.

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Tree ferns in dappled sunlight, Cornwall
© Getty

How to feed tree ferns

During the spring growing season, feed weekly into the crown of the tree fern as the knuckles start to move and the fronds begin to unfurl. Use a specialist feed – HSK Tree Fern Feed – it is by far the best. If they have suffered a particularly rough winter they will really benefit from this boost.

What to plant with tree ferns

Topiarised evergreen balls and pillows are a good architectural contrast to accompany tree ferns when underplanted. Taxus baccata, Ilex crenata ‘dark green’, Hebe paviflora ‘angustifolia’ and Hebe sutherlandii work well. Fatsia japonica and other big tropical shade loving plants balance the surrounding space and add additional textures along with, Pittosporum tobira with its lovely rich green glossy leaves. Phormium tenax ‘Variegatum’ provides an excellent colour contrast to the trunk of a tree fern as well as accentuating the vertical drama. We also love using the defined and structural, Mahonia ‘Soft Caress’. You might want to consider developing a bigger fernery, underplanting with other smaller evergreen ferns such as, Pellaea rotundifolia, Asplenium scolopendrium, Blechnum chilense and Polystichum munitum or other ground cover plants such as Luzula nivea or Pachysandra terminalis.

 

When to cut back tree ferns

One of the many wonderful things about a tree fern is that there is very little creative maintenance required, short of cutting off old or damaged fronds after the last frost.

When do tree fern fronds appear?

New fronds develop in the spring. The rate of growth varies enormously, according to microclimate and soil conditions. An okay Dicksonia antarctica will produce a new rosette of fronds in the spring and then stop growing until the following spring. A happy Dicksonia antarctica will do the same, but then just carry on chucking out new fronds at an extraordinary rate. The idea that these grow very slowly – especially when young – is untrue. Give them the right conditions and they let rip. Back in 1990, we sent some tiny homegrown plants in a box to Philip Brown at Portmeirion, to a spot very protected by trees, but right on the Atlantic coast in North Wales. We visited two years later and couldn’t believe our eyes. They were all 12ft across with 1ft trunks. Quite a revelation.

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