HOW TO OVERWINTER TREE FERNS

How to overwinter tree ferns

Tree ferns are among some of the world's great architectural garden plants, and while they are native across the tropical and subtropical areas regions of South Africa, Australia, Tasmania, New Guinea and New Zealand there are a number of the thousand or so species which are hardy enough to survive planted outside in northern European countries. In fact in the milder regions of southwest England there are areas where species such as Dicksonia antarctica have been left to their to their own devices quite successfully for almost a century.

Of course, shipping tree fern trunks halfway across the world can make them an expensive purchase so to ensure that your prized specimen survives year after year it is prudent to put in place suitable cold protection so that they can survive our freezing winters relatively unscathed.

How to overwinter tree ferns

The new growth of tree ferns is produced at its crown, although side crowns can occur on mature specimens. While thick taproots run from the crown down through the trunk and into the soil the thick fibrous qualities of the trunk is usually enough to provide adequate cold protection for this specialist above-ground root system.

The crown of the tree fern is another matter and will require cold protection, especially the further north they are planted. The old brown, dried fronds can be packed into the crown, alternatively use bracken or straw. Do not push your protective material to hard into the crown as this can cause damage to the tightly wound 'embryonic' fronds known as crosiers. This level of protection will be perfectly adequate for the south of England and should be put in place before the first hard frosts - usually october to November.

Further north and the longer freezing temperatures will require an upgrade in cold protection. Gather the fronds around the crown and tie them up. Wrap the entire plant in layers of frost protection fleece. The colder the temperature the more layers will be required.

For less hardy specimens such as Dicksonia squarrosa, Dicksonia fibrosa and Cyathea dealbata pack the fleece with a thick layer of straw or bracken.

Take off the protective fleece in the spring, and remove the crown protection before the new fronds come into growth. Container grown plants in milder areas should be placed under protection in a sheltered frost-free position with the container bubble-wrapped to prevent the roots from becoming cold damaged. Countries with a more arctic winter such as Canada, or Scotland tree ferns are best lifted and brought into a frost-free conservatory or greenhouse.

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