What you need to know about tree ferns for a cool climate

March 1st, 2020
Posted In: Gardening know how

Tree ferns look exotic but they can withstand some frost and snow.

They grow well in small urban gardens, where they can be sheltered by house walls.  They are one of the key plants in today’s fashionable layered jungle garden planting.

Tree ferns growing wild

See plants growing in the wild teaches you so much about how they like to grow in your own garden. This is original rainforest with wild tree ferns. It’s cool and shady.

So if you want an exotic garden in a cool climate, what do you need to know about tree ferns? I asked Stephen Ryan, broadcaster and rare plant specialist, whose nursery is called Dicksonia Rare Plants near Melbourne.

Stephen also has a YouTube channel, called The Horti-culturalists, with Mathew Lucas.

How to choose a tree fern for a cool climate

Stephen says that the most important thing is to buy from a reliable and experienced stockist of tree ferns. In a cool climate, you should buy Dicksonia tree ferns, which are frost hardy down to around minus 5 Celsius.

There are many types of tree ferns, but only Dicksonias (Dicksonia Antarctica) and Cyatheas will survive in a temperate climate. And Cyatheas are not reliably frost hardy so you would need to keep them in a greenhouse or conservatory in the winter.

Tree Fern planted in the 1880s

This beautiful tree fern was planted when this house was built in the 1880s. It has survived some harsh winters, hot summers and even a bush fire that came very close.

Dicksonia Antarctica are often sold as a log, with the ferns and roots cut off. This is because the whole trunk is a root system and it can be simply planted in the ground. But, of course, you can’t tell how healthy the plant is until the fronds emerge. That’s why you need to buy from a reputable dealer.

How to plant tree ferns

Stephen says that you plant a tree fern just as you would any other plant. Give the soil a good mulch, dig a hole and put the tree fern in. Backfill with soil and compost and water well.

‘But if you have just bought a trunk,’ he says, ‘you’ll need to plant it deeply enough into the ground so that it won’t topple over. This means losing about 12″ of height. So remember that when you are ordering. If it comes with a rootball base, that’s less important.

You also need to support it until it establishes. Unusually, however, you can place rocks or stones in the planting holes to help hold it up. Because the whole trunk is a root system you won’t cause problems with the roots the way you would if you did this with an ordinary tree.

Where to plant them?

Tree ferns like light, but they can burn in direct sunlight. They are happiest under a light canopy of other trees.

If you have a sheltered spot in a courtyard that gets some filtered light, that’s perfect. They’ll also handle shade well.

Keep away from harsh winds or anywhere exposed.

How to water a tree fern

These plants like a fairly damp climate. So you should water them in a drought. Stephen runs a hose over the whole trunk (because it’s a root system). He then returns a few minutes later and repeats it, because if a tree fern trunk has got very dry it may not absorb much water. He sometimes repeats that three or four times.

Stephen says there is some debate about whether you can water tree ferns from the top. Some people believe it will cause the crown to rot. ‘However, I’ve watered my tree ferns from the top and have never lost any that way,’ he says.

He often perches the hose on the top, wedged between the stems, and lets it drip down for a few hours. ‘Although be careful not to damage the young croziers by poking too hard down into the crown,’ he adds.

‘And don’t water them from the top in winter because if water freezes in the crown, that will damage them.’

Do they need fertilising?

In the wild, tree ferns benefit from falling leaves on the forest floor. These rot down into mulch, and Stephen says that a once a year mulch with garden compost or rotted animal manure is all a tree fern needs in a garden. ‘I’ve never given my tree ferns any extra fertiliser,’ he says.

It’s different if it’s in a pot because it can’t take nourishment up from the soil through its roots. You will need to fertilise it.

How to protect tree ferns in winter?

Stephen lives in a mountain area near Melbourne, so the winters do get cold. But they don’t have sustained frost and snow for weeks on end.

The wild tree ferns in the gully near where he lives have been covered in snow several times. But not for long.

Tree ferns grow wild

So tree ferns can cope with a bit of frost and snow. ‘But if you get sustained sub-zero temperatures so that the trunks freeze, then you’re in an area where tree ferns probably won’t survive,’ he says.

Stephen stuffs some straw gently into the crown to protect the young croziers (fern leaves) from frost. Other people wrap their tree ferns in horticultural fleece or bubble wrap if sustained cold weather is forecast.

Dicksonia tree fern crown

The crown of a tree fern. Stuff it gently with straw to protect from frosts. If your frost is going to be very hard or likely to last some time, you may need to wrap the whole plant in horticultural fleece, but Dicksonias can take a few degrees below freezing, provided it doesn’t last too long.

If your tree fern is in a pot, you may be able to move it closer to the house. The best protection is to plant tree ferns in a sheltered spot, away from frost pockets or nasty winds. Generally a house wall will be a warmer place for a plant in winter.

Pruning tips

Tree ferns don’t actually need pruning, says Stephen. When the unfurled croziers go old and brown, you can cut them away.

However he warns against over-zealous trimming. ‘If you take away all the old growth, you expose the new growth to wind and weather,’ he says. ‘And you also get a shuttlecock effect. I think they look better with some natural curve to the leaves.’

Can you move a tree fern?

Stephen says that you can move a Dicksonia tree fern in two ways. Firstly, you can simply cut the trunk off wherever you like and plant it in the ground. ‘But don’t forget that you’ll lose the height and tree ferns are very slow growing.’ The rootball you leave in the ground won’t grow into a tree fern again. However the trunk is a root system and can be planted straight into the ground.

Or you can dig up a tree fern with its root ball and re-plant it. This is hard work but will maintain the height. And you don’t need to dig up the entire root ball – you can cut around the roots in the ground, although you will need to support it.

There is a video here showing how to move a tree fern:

Why isn’t my tree fern growing?

If the fronds are going brown, Stephen says it is nearly always a water issue or it’s being burned by being in too bright a spot.

‘Either you’ve placed your tree where there’s too much direct sun or you haven’t been watering the trunk enough,’ he says.

If you’ve bought your plant recently, it may not have been looked after properly. The fronds may be damaged or they may be small. It could take several years for them to grow well.

If you want to check whether the tree fern is dead, Stephen says put your fingers down into the crown very gently. If you can feel the croziers and they are soft and supple, they’re alive.

‘But if they feel dry and crispy, you’ve lost your tree fern,’ he says.

But don’t throw away a dead trunk. It’s a wonderful habitat for other plants and for insects. It rots down very slowly so it can sit in your garden covered in moss, alpines or ferns for years.

See more in this video:

More about Stephen Ryan

You can find Stephen Ryan’s Dicksonia Rare Plants in Mount Macedon, Victoria. Or book him for talks, discover his garden tours or visit his garden by visiting StephenRyan.com.

There are some of his garden improvement tips here in 13 clever ways to improve your garden.

Stephen Ryan

Stephen Ryan in his own exotic themed garden.

Or read Stephen’s advice on choosing and growing rare plants and creating an exotic garden for a cool climate.

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Tree ferns for a cool climate


20 comments on "What you need to know about tree ferns for a cool climate"

  1. Debby says:

    Our temperature erasures here is going down to 3c should I wrap the top part of the tree in fleece? My only concern is watering when it is wrapped in a fleece. It’s in a pot outside. Where do I water the fern when I have put straw in the centre and it’s wrapped in fleece?

    I loved this article and you tube videos. It would be lovely to see how it be is properly wrapped up in my detail. There’s not much out there which is really helpful when you have a potted plant.

    1. I think the tree fern is probably fine at 3C, it’s when goes down to minus that it may struggle. I haven’t grown a tree fern in a pot myself, and I think it might be best to ask a company that supplies tree ferns, such as Paramount Plants or Architectural Plants. I hope that helps.

  2. Jez Davies says:

    I have kept a reasonably large (6ft) Dicksonia in a big pot for about 6 years now, outdoors in the south of the UK. It seems pretty happy. My question relates to watering over winter. Common advice is to avoid due to potential damage to the crown if it freezes, but how about if freezing is unlikely? Do tree ferns go to sleep over winter and not require manual watering, able to get by with whatever rain occurs?
    Due to being in a pot, this one will not benefit from general ground water, and the soil can dry out quite quickly. I have never watered over winter before, waiting for spring and the removal of fleece and straw before starting a regular watering regime, but is that right? Would my fern prefer to get the odd winter water so long as it isn’t too cold?

    1. It seems to be doing well on the way you are treating it now, so I wouldn’t see an advantage in changing what you’re doing. Most plants go dormant or semi-dormant in the winter, so drying out is less of an issue.

      1. Keith Allam says:

        I have been growing tree ferns for years in south of England. I would strongly refrain from top watering in winter. The UK climate is generally wet enough. If your T.fern is in a sheltered dry position I would water the bottom 1/3 of the trunk and pot only. When the season moves on and temperatures improve then revert back to top watering, but only if there is no immediate chance of frost.

        1. Thank you for sharing your experience with us.

  3. Jill says:

    Hi, I’ve had a tree fern in my garden (just north of London) for a few years now. The crown seems to be getting narrow, and the fronds have not been as huge as when I first got it. Does this mean that it will never have big fronds or does the size of the crown not matter? Thanks.

    1. I understand that this can be because it’s not getting enough water. Try watering more and see if that helps.

  4. Ben says:

    Hey I’ve got a 3ft tree fern, it’s my favourite plant and it makes me think about living in a Jurassic time period – living in the uk when (month) will the fronds start coming out?
    Thank you.

    1. Probably spring, so it should be round about now, although we are having a very cool spring.

  5. Dave Richards says:

    I recently bought a 5ft tree fern , as the croziers emerge they split and ooze a brown substance, any ides what it might be

    1. I’m sorry, I’m not sure – can you contact the seller? I did a quick look online, as you probably did, and it didn’t come up anywhere except for one conversation from someone who thought it was the normal sap. It might be worth seeing if it settles down when the tree fern gets established, and that will be at least a season. Hope that helps, sorry it’s a bit vague.

    2. Patrick Hendrick says:

      I had a red brown ooze last year when i removed the straw from the crown after the winter. The tree was ok, produced a really good show of fronds. I feed it once a week. Ill know later this week whether its done the same this year



    MONTY DON SAID ON GARDENERS WORLD THAT TREE FERNS ARE ENDANGERED AND WHEN YOU BUY A TREE FERN TO MAKE SURE THAT IT HAS COMEE TO THE MARKET LEGALY – The tree fern came with an official licenced tag saying it had been harvested from an official tree fern forest.



    1. Yes, you’re right, that’s a very good point, thank you. Another reason to buy from a reputable grower.

  7. Cynthia Walker says:

    I had never heard of a fern tree until I came across your blog here. I would love to have one in my yard, but I don’t think it could handle the possible -20 we get here in Anchorage during the winters along with 80+- inches of snow! But I did love reading and learning about them. Thank you for sharing!

    1. Yes, that does sound very cold. I think tree ferns might demand a heated conservatory…thank you.

  8. Maggie says:

    This was very helpful information.
    I was given a Dicksonia tree fern as a Christmas present. I unwrapped a brown hairy log, which I planted in a large, holey bucket; soused it with water and put it in our very light and airy shed. The plan was to keep it in a pot – I was scared to plant it outside in case we had snow and ice like last year. And I’m in Scotland. Within a fortnight it started putting out fronds. There are three now and the first is nearly a metre long. Your article has emboldened me to plant my tree fern into the garden and just be ready with the fleece if needed. Thank you.

    1. That sounds fabulous. It’s obviously a very happy tree fern. I hope it goes well.

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