Dicksonia antarctica and winter protection

[Weekend Gardener]

How much winter protection does Dicksonia antarcticarequire in the Lower Mainland in BC? I am on the Northeast facing slope of a hill and the average lowest temperature has been around 10 Celcius in the last 9 years. Or should I keep it in the pot, since it's still somewhat small. I have only just got it and it hardly has any trunk at this point.

[Alex Downie]

Dicksonia is only half-hardy in the Vancouver area. This depends a lot on where you are. The nicest ones are planted in a building entry atrium open to the street next door to the Liquor Store at Alberni St near Thurlow St. Most of us don't have such protected situations, though!

The other factor is that it has been quite a few years since we've had a real hard winter. Dicksonia can easily tolerate -7 C for a few days, but prolonged freezing, or temperatures below this can definitely spell trouble.

VanDusen Botanical Garden has a group of these tree ferns in their Sino-Himalayan Garden in Shaughnessy, at about 350 ft above sea level. They are planted under a grove of Douglas Firs, in a woodland garden situation. an ideal habitat. They protect their ferns using a chicken wire enclosure stuffed with dry oak leaves. The top portion of the enclosure is then covered with plastic to keep moisture out. The leaves are cut off entirely before the stems are wrapped up in late November. The covering is removed in mid-March and the ferns grow a new crown of leaves shortly thereafter.

It is very important to ensure the covering is watertight at the top to prevent moisture from freezing in the crown of at the top of the stem. I lost a 3 foot stemmed Dicksonia in my North Vancouver garden after a -9 C freeze because the covering wasn't watertight.

I would keep your fern in its pot this winter so you can bring it indoors when freezing temperatures threaten. Plant it in the ground in early April. It will then have a whole growing season to become established. Then protect it through the winter. Note that young trunkless Dicksonias are more tender than older trunked ones.

A north facing aspect is good. Tree ferns are not drought tolerant! A shady location will experience less dramatic thaw/freeze cycles during cold spells which occur when the early morning sun strikes the frozen plant.

Good luck!

[Ron B]

In other words, they're not really hardy at all.

[Weekend Gardener]

Thanks, Alex! That's really useful advice.

I will keep it in the container. I have a cold greenhouse, capable of being keep at zero degrees celcius when the ambient temperature is -10 outside. (Can you believe it, with Christmas decoration lights to provide heat during those brief periodes! And it's quite a sight too!). I plan to keep it containerised for at least 3-5 years because I want it on a first floor deck.

Can it tolerate minor freezes, at say, down to -3 to -5 celcius?

[mar]

can the tree ferns be pruned....I have an area about 10 ft high, protected, north facing,,,,it would be ideal for a tree fern....my question is how high do they grow and how fast.....the area is warm and protected...even the bulbs I just planted in that spot are starting to sprout....

[mar]

I have just purchased a dicksonia antartica and want to find the best spot for it...I have a covered area , really protected that is about 10 ft high....north facing.....the bulbs that I just put in a month ago are starting to sprout because the area is warm and covered , close to our house and has a window which I suppose gives extra warmth , like an atrium....Is it enough space 10ft high 10 ft. wide....How fast do these plants grow and can they be pruned back if it outgrows the space.....we live out by the UBC botanical gardens.....I think the space would be perfect.....but maybe not if it grows 50 ft . high ?

[Eric La Fountaine]

Hey Mar, I merged both of your posts into this thread on D. antarctica to keep the conversation in one place.

I don't know about pruning, but the fern is going to be somewhat tender in this climate, so protection will be needed to get it established. In rare situations D. anarctica have grown to 50 feet, but 20' would be closer to the average mature height. They are very slow growing, depending on climate, they grow around 1 to 3 inches per year. Here in a cool climate it is likely to be closer to the 1 inch per year rate. Mature specimens will be more cold hardy and then the "tree" may survive outdoors without winter protection.

[Ron B]

Sunset Western Garden Book says "Hardiest of tree ferns; well-established plants tolerate 20F/-7C."

In addition to those at the VanDusen garden, you can see some at Hatley Castle, near the lagoon.

http://www.hatleycastle.com/index.html