Why Small Spaces Feel the Frost More

If you garden on a balcony, a courtyard or a narrow strip of paving, you will already know that frost bites harder in a confined space than it does in a big open garden. There is simply less air to buffer the cold, less soil to hold warmth, and far more hard surfaces in the form of walls, fences and paving that radiate the day's heat away with alarming speed once the sun goes down. Pots are the biggest risk of all, because a plant's roots sit above ground in a small volume of compost that freezes from the outside in.

The good news is that small spaces are also easy to protect. You can reach every plant, move every container and cover a whole growing area with a single sheet of fleece. A little planning on a mild afternoon saves a great deal of heartbreak when the first proper cold snap arrives.

Move Tender Pots Under Cover

The single most effective thing you can do is also the simplest: move pots. Anything tender that lives in a container can be lifted, and a few feet of shelter makes a real difference. Aim to get plants against a house wall, under an overhang, or inside a porch, greenhouse or cold frame before dusk rather than in the morning, when the damage is already done.

• Group pots together in a tight cluster against a south- or west-facing wall. Massed containers trap warmth between them and shield one another from wind.
• Raise pots onto feet or bricks so they are not sitting directly on freezing paving. Cold travels up through the base of a pot faster than most people realise.
• Prioritise the vulnerable — citrus, fuchsias, pelargoniums, bay, olives, young cuttings and anything newly planted. Hardy shrubs can usually stay put.
• Check drainage before you move anything. A pot that sits in a saucer of water is far more likely to lose its roots than one that drains freely.

If you have no indoor space at all, a cardboard box lined with newspaper and tucked behind a sheltered wall will carry most small pots through a couple of sharp nights.

Wrap Containers in Bubble Wrap

Insulating the pot itself is the trick many small-space gardeners miss. It is not the leaves that suffer first — it is the rootball. Terracotta and thin plastic both conduct cold straight through, so a layer of bubble wrap around the outside acts as a duvet for the roots.

• Wrap the sides and base, securing the bubble wrap with string or tape. Leave the top of the compost open to the air so the plant can still breathe.
• Double up on small pots, or stand a smaller pot inside a larger one with scrunched-up newspaper in the gap.
• Push a layer of mulch — bark chippings, compost or even loose leaves — over the surface of the compost to insulate the crown of the plant.
• Remember raised beds and troughs. They freeze from the sides just like pots, so a wrap of bubble wrap or old fleece around the outer face is worth the effort.

Get the Watering Right

Watering late in the day is one of the most common causes of unnecessary frost damage. Wet compost freezes far more readily than dry compost, and a plant sitting in damp soil overnight has much less natural protection. When a cold snap is forecast, water in the morning instead, and only if the plants genuinely need it.

It also pays to cut back on watering altogether during a cold spell. Growth slows, so plants use far less water, and soggy roots in freezing conditions rot quickly. If you must water, use water that has been standing in a can indoors rather than straight from a cold outdoor tap, and aim it at the compost rather than the leaves. Avoid feeding too — a flush of soft new growth in midwinter is exactly what frost loves to attack.

Fleece, Cloches and Other Quick Covers

For plants that cannot be moved, a physical cover is the next best thing. Horticultural fleece is inexpensive, lightweight and can be draped directly over plants, held down with a few stones or pegs so the wind does not whip it away. Cloches, bell jars, upturned clear plastic bottles and even old windows propped on bricks all work well for small plants.

• Take covers off during the day if the weather is bright, so plants get light and air and do not stew.
• Do not let covers touch the foliage where you can avoid it. Where plastic meets leaf, moisture condenses and freezes.
• Water the soil, not the cover, and avoid trapping pools of water under the material.

A Simple Frost-Ready Routine

Keep an eye on the forecast and, on the day a cold night is predicted, run through the same short list: move what you can, wrap what you cannot, mulch the surface of the compost, and stop watering after midday. It takes perhaps twenty minutes and will save you a season's worth of plants. Small-space gardening is all about making the most of limited room, and a little shelter is the cheapest protection you will ever buy.