House plants under light in winter

How not to kill your house plants this winter

The world went house plant crazy over lockdown, but what do you do with your house plants now winter is coming? Here are a few dos and don'ts for your indoor plants this winter

As the days shorten and temperatures drop outside, tending our indoor jungles becomes ever more important for our winter wellbeing, but there’s a snag: this time of year can be tough on house plants.

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The causes are multiple: central heating dries the air, wood burning stoves and open fires can make rooms too hot, nighttime temperatures may drop too low for some house plants, especially if they are tucked behind closed curtains, and lower light levels can cause succulents to stretch and flop.

Prayer plants illustration
© Patrick Morgan

If you’re anything like me, your collection will have ballooned over summer, with new plants being added to the ranks almost weekly. Now it’s time to move specimens that have spent the summer on the patio or balcony inside, things may be getting crowded indoors. How do you keep all those house plants happy? Here’s what to do.

Rearranging house plants in winter
Rearranging house plants in winter
© Jane Perrone

House plants in winter: how to care for your indoor plants

Boost air humidity

One of the best ways you can combat the dry air that comes with central heating is by grouping house plants together to create their own more humid microclimate. Pop pots onto a tray full of wet pebbles, grit or leca (expanded clay pebbles) and the water will add moisture to the air as it evaporates. Kitchens and bathrooms can also be great locations for plants that need a humidity boost. It’s tempting to think that misting is the solution to dry aid, but this is such a temporary fix that it doesn’t really help plants, plus wetting leaves can encourage fungal conditions.

Window ledges that trap plants in a cold patch behind curtains are bad news for many tropical and subtropical species

Also take a look at potential troublespots: shelves above radiators or heating vents will mean certain death to most house plants, and window ledges that trap plants in a cold patch behind curtains are bad news for many tropical and subtropical species. If you have succulents and cacti, the regime they need over winter is rather different: these will benefit from a cool room with bright light, so if you have an unheated spare room or south-facing porch, move them there.

Let in the light

Moving house plants closer to windows in winter will help to maximise their available light, as will removing net curtains and making sure curtains and blinds are fully open as soon as the sun comes up. LED growlights are now widely available and offer a way of boosting light levels over winter: set them up on a timer to come on for around 12 hours a day to save yourself the hassle of switching them on and off. (Opt for bulbs marked ‘full spectrum’ if you want to avoid that pinky-purple glow which neighbours may confuse for a cannabis-growing side hustle.) Most house plants will need to be positioned around 30cm away from the light source: seedlings and succulents can be placed a little closer.

House plants under light in winter
House plants under light in winter
© Jane Perrone

Ration the water

Most house plants will slow growth a little over winter: some will go completely dormant. As a result, they’ll need less in terms of water and nutrients. Waterlogged roots are a major cause of plant death, especially for cacti and succulents. If your cacti and succulents are at regular room temperature, they will need watering during the colder months, but only when the potting mix is almost completely dry: in unheated rooms, they may not need any water at all. Tropical foliage plants, ferns and the like can be watered only once the soil feels almost dry at the root level (use a moisture meter, or just stick your finger into the rootball and see how much compost clings to it). Make sure you drain away any excess water that gathers in saucers and cachepots, and allow water to reach room temperature before applying to the soil, so that house plants don’t get an icy drenching.

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Succulents and house plants under growlights for winter
Succulents and house plants under growlights for winter
© Jane Perrone

Pest patrol

Winter can cause house plants stress, and stressed plants are much more prone to attacks from pests. Plus, if your leafy charges have enjoyed a summer holiday outside, they may have come back inside with some hitchhikers on board. Examine the bottom of pots for lurking slugs, and check leaves carefully for aphids and spider mites, concentrating on the undersides of leaves and any new growth. A hand lens is a great investment too; highly useful for spotting spider mites which are too small to be seen with the naked eye. The sooner you spot infestations before they take hold, the easier they are to deal with. Invest in a bottle of SB Plant Invigorator as a pesticide: it’s safe for use around children and pets and can be sprayed regularly to deal with spider mites, aphids, thrips and so on. Wiping leaves regularly with a damp cloth is good house plant practice whether you have a pest issue or not, as it helps keep stomata (the leaves’ breathing holes) clear of dust and other debris. This may feel like a chore, but treat it as a mindfulness exercise and it may even help you pass the winter in a house plant-induced state of bliss.

Jane Perrone is crowdfunding Legends of the Leaf, a book about houseplants, at legends-of-the-leaf