Why British winters are tough on houseplants

Most of the plants we grow indoors come from tropical or subtropical corners of the world, where the light is strong, the air is humid and the nights are warm. A British home in January is none of those things. Daylight hours shrink to around eight, and even a bright south-facing windowsill may only get a fraction of the light it received in June. Add central heating, which dries the air to desert levels, and single-glazed sash windows that drop close to freezing on frosty nights, and it is no wonder plants sulk.

The good news is that most houseplants do not die in winter — they simply slow down. Your job is to work with that slowdown rather than against it. Think of it as a resting period, not a growing one, and almost every decision you make between November and March becomes easier.

Ease off the watering can

Overwatering is the single biggest killer of indoor plants in winter, and it is almost always done with good intentions. Cool compost, weak light and lower temperatures mean roots take up water far more slowly. A plant that drank its pot dry in four days in July might take three weeks to do the same in December.

Before you water anything, push a finger two to three centimetres into the compost. If it feels even slightly damp, walk away and check again in a few days. For larger pots, a bamboo cane or wooden skewer pushed down to the base works well — if it comes out clean and dry, it is time to water.

• Water less often, but thoroughly. A proper soak every two to three weeks suits most plants better than a daily splash.
• Always use tepid water. Cold tap water straight from an outdoor tap can shock tropical roots.
• Empty saucers after ten minutes. Standing water in a cold room is a fast route to root rot.
• Leave cacti and succulents almost dry. Many can go from October to March with barely a drop.
• Never let plants sit in a cold puddle on a windowsill overnight — that is how crowns and stems rot.

Find the right spot — and dodge the draughts

Light is scarce, so moving plants closer to a window genuinely helps. But a windowsill is not automatically the best place. On a clear frosty night, the air immediately behind the glass can be several degrees colder than the rest of the room, and a plant pressed against it may suffer chilled, blackened leaves by morning.

The practical compromise is to bring plants closer to the glass by day and pull them back at night, or to slide a piece of card or a thin sheet of bubble wrap between the pot and the pane. If you have blinds or curtains, closing them between the plant and the window traps a layer of insulating air — just make sure the leaves are not crushed against the fabric.

Draughts matter just as much as cold. A plant sitting in the path of a door draught, an extractor fan or a badly sealed letterbox will drop leaves and refuse to recover until spring. Grouping plants together helps: they shelter one another and create a slightly more humid pocket of air around their leaves. Just leave a little space between pots so air can still move and mould does not take hold.

Clean leaves, discourage pests

Dust settles on leaves over winter because windows stay shut and rooms are heated. A layer of grime blocks the light that plants are already short of, so a monthly wipe is one of the most useful jobs you can do. Support each leaf with one hand and wipe gently with a soft damp cloth or a piece of kitchen paper, working from the stem outwards.

Fuzzy-leaved plants such as African violets dislike wet foliage — use a soft dry brush instead. For ferns and small bushy plants, a lukewarm shower in the bathroom works beautifully, provided you let the pot drain properly afterwards.

While you are cleaning, look closely at the undersides of leaves and where they join the stem. Winter is peak season for pests indoors, and warm, dry, still air suits them perfectly.

• Mealybugs look like small balls of white cotton in leaf joints. Remove them with a cotton bud dipped in diluted washing-up liquid.
• Spider mites leave fine webbing and a speckled, faded look on leaves. Raise humidity and wipe leaves regularly.
• Fungus gnats hover above wet compost. Let the top layer dry out and water from below for a few weeks.
• Scale insects appear as small brown bumps along stems. Gently scrape or wipe them away.
• Quarantine any new plant for a fortnight before introducing it to your collection.

Hold back on feeding, repotting and pruning

With light levels low, most houseplants cannot use extra nutrients, and feeding them now encourages weak, pale growth that pests love. Pause liquid feed from late autumn until you see fresh signs of growth in early spring, usually around March. The exception is any plant flowering happily under a grow light.

Repotting is best left until spring too. Disturbing roots when a plant is resting does far more harm than good, though you can top-dress a pot with a centimetre of fresh compost if the surface has sunk. Tidy off dead or yellowing leaves with clean, sharp scissors, but avoid hard pruning — those leafless stems are stored energy the plant will draw on in spring.

Finally, keep plants away from radiators and hot air vents, and accept that a little leaf drop is normal. Water sparingly, keep the leaves clean, shield them from cold draughts, and by the time the days lengthen your plants will be ready to grow away strongly.