If the weather suddenly turns cold, early-flowering and tender plants may need special protection to avoid damage caused by freezing temperatures.

There are several ways you can provide winter protection, including mulching, covering the plants, moving them, or by taking advantage of a light snow covering.

Mulching is one of the best ways to protect plant roots. Bark, straw, sawdust, peat, coir moss, leaves and even grass clippings are the most common mulching materials.

Remove the weeds (if possible) before applying the mulch. As a rule, the mulch should be about 5cm deep. Keep the mulch 2-3cm away from the trunk or main stem of the trees and shrubs to avoid scorch.

Again, there are exceptions, such as roses and cane berries, where the mulch is actually mounded over the canes. Then, when spring arrives and after all danger of frost has passed, these mulch materials are pulled away.

It is important to note that the combination of dry soil and cold temperatures can cause serious freeze damage to garden trees and shrubs. In fact, you may need to water in mid-December or mid-January if you find the soil dry.

Covers are the most effective way of protecting the foliage of broadleaf evergreen shrubs. Rhododendrons, camellias, azaleas and early-flowering plants will often benefit from being covered during extremely cold weather.

Start by placing three or four stakes around the plant being protected. Next, drape a cloth over the stakes, being careful that it does not come into contact and freeze on the leaves.

Do not use clear polyethylene for this job, as it not only cuts off air to the plant, it also acts much like a greenhouse, taking plants from nightly lows to high daily temperatures in a short period of time. This rapid temperature change can cause serious freeze damage or may be fatal to plants.

Any type of covering should only be left in place during the cold spell. As soon as the weather moderates, or it begins to rain, remove the covering completely. However, leave the stakes in case it gets cold again.

Hessian, old blankets, sheets, porous spun fibres or similar cloth or fabric materials are the best types to use as a cover over plants.

Mother Nature actually provides the best blanket of protection in the form of a light snow. Up to 5-7.5cm of snow not only insulates the ground around your plants, it also provides a blanket of protection over the leaves.

On the other hand, heavy, wet snow can cause considerable damage as it tends to place too much weight on the leaves and branches, often causing them to break. So, if the snowfall is wet and heavy, you should shake off the excess snow before any damage occurs. Try to do this carefully so some snow remains as a winter protection.

One of the easiest ways to give plants winter protection is to simply take them into a garage during a cold spell. Once the weather improves, put them back outside. Do not leave the planted containers inside all winter, unless you have a greenhouse or sun-porch.

The key thing here is to enable good drainage. Slightly raise the container off the ground on bricks or feet'.

Tender perennials like chrysanthemums and hardy fuchsias can be covered with only about 2-3cm of straw during a cold winter or move them to a frost free glasshouse. (In a mild winter, this is usually not necessary.) Half-hardy summer annuals like stock and snapdragons are only two prime examples of annuals that will sometime become perennials and winter-over if given a little mulching attention. Straw, bark or sawdust are the best materials to use for mulching over these plants. Use only about 2-3cm of mulch.

Half-hardy shrubs and vines like bougainvillea, hibiscus, gardenias, mandevilla, citrus, should be treated as indoor houseplants over-winter.

Happy gardening.
Send your questions and SAE to
Tom Cole
Head of the London School of Horticulture and Landscaping
Capel Manor College
Bullsmoor Lane
Enfield
Middlesex
EN1 4RQ
or email him at Thomas.cole@capel.ac.uk