How do I wrap a tree fern or banana for winter?

Most winter losses in these plants are rot rather than cold — water sitting in the crown, freezing, and killing the growing point. A wrap that keeps the plant wet is worse than no wrap at all.

What you'll need

• Horticultural fleece or hessian
• Dry straw or dry leaves
• Chicken wire
• String
• Waterproof cap or upturned pot (optional)

Step by step

1. Wait for the first frosts.Wrapping too early keeps the plant soft and encourages growth into November. Wait until growth has stopped and the first frosts have hardened it, usually late November.
2. Protect the crown first.On a tree fern, the growing point sits in the centre of the crown at the top of the trunk. Pack it loosely with dry straw or dry oak leaves — this is the part that must survive.
3. Keep rain out of the crown.A waterproof cap, an upturned pot, or fleece topped with a plastic sheet that sheds water. Straw that gets soaked and freezes is worse than nothing.
4. Fold the fronds up and over, or remove them.On a tree fern in a mild area, tie the fronds up over the crown as extra insulation. In a colder area cut them off and rely on the packing.
5. Wrap the trunk in a breathable material.Hessian or horticultural fleece, several layers, tied with string. The trunk of a tree fern is a mass of roots and must not dry out completely, so breathable is important.
6. Use a chicken wire cage for bananas.Cut the leaves off, wrap the stem in fleece, then build a chicken wire cylinder around it and pack it with dry straw or leaves, with a lid to shed rain.
7. Do not use plastic against the plant.Plastic in direct contact traps condensation and rots the tissue. If you use a plastic outer layer, keep it clear of the plant with wire or straw beneath.
8. Mulch the root area.A thick mulch over the roots protects them and matters more than people expect for bananas and gingers, which regrow from the base.
9. Ventilate on mild spells.A long mild wet December is more dangerous than a hard frost. Open the top on mild days to let the packing dry.
10. Unwrap in April, in stages.Remove the outer layers first on a mild day, then the packing a week later. Leaving it on into May cooks the crown and encourages rot.

Tips

• It is rot, not cold, that kills most of these plants. Keep the crown dry above all.
• Never put plastic straight against the plant.
• Take the wrapping off in April. Leaving it on too long causes as many losses as not wrapping at all.

Common mistakes

• Wrapping the whole plant in plastic sheet — Condensation forms inside, cannot escape, and the crown rots. Use breathable fleece or hessian against the plant, with any waterproof layer held off it.
• Packing the crown with damp material — Wet straw freezes into a block of ice around the growing point. Only dry straw or dry leaves, and only under a cover that sheds rain.

If it doesn't work

Questions people ask