How to tend indoor plants in winter | James Wong

Bringing plants inside isn’t always an act of kindness if you overwater or overheat. Here are the rules for keeping them happy and healthy through the cold season

I am more than happy to admit that I am a fair-weather gardener. With the past week of relentless rain, mist and mud, thank goodness for indoor plants. They offer me the chance to be surrounded by growth and life, even in the darkest depths of winter.

However, just as with exterior plants, seasonal changes will affect how you garden in the great indoors. In fact, for many houseplant species, understanding this shift can mean the difference between being an easy-care option and one that will really struggle for you. So here are the three things to remember as you tend to your indoor Eden over winter.

Most modern homes don’t suffer a significant drop in temperature in winter, but they will have far lower light levels as the nights draw in. As plants are essentially living solar panels, this slowing of their energy supply means some struggle. Light-lovers, such as cacti and succulents, often become long and leggy as they attempt to stretch toward a light source to eke out the winter rays. Others, such as citrus and pileas, will start to abort their leaves, exhausted by the lack of light energy to match their fast metabolism in a warm room.

There are two simple tricks to overcome this. First, simply move your plant closer to a window. Ledges that can scorch plants with searing UV in summer often become the perfect “bright but indirect” houseplant habitat in the winter. The one caveat is to avoid placing them near radiators, whose high localised heat levels can literally cook plants.

Alternatively, move your plant to a cooler room – counterintuitive, I know. You see, many plants won’t mind lower light levels as long as they are paired with cooler conditions. This dip in temperature slows their metabolism, so they won’t require as much solar energy. Most houseplants will fare better with temperatures of 15C or so in winter if you can’t boost light levels. An unheated porch or conservatory is a great spot.

As plant growth rate slows in winter so does their requirement for water and fertiliser. As the number-one killer of houseplants is usually overwatering, you might need to cut back your use of the watering can by half (or even more) in winter, so your plant’s roots don’t sit in damp sogginess and become prone to rot. With my 500 houseplants, for example, I am watering once every two to three days in summer to beat the heat, but in winter I have left them for as long as a fortnight at a time with no visible signs of stress. Some commercial growers of drought-tolerant species will almost stop watering altogether for months on end, with this winter rest period being a key biological trigger for larger flowers and more vivid colour.

Finally, winter is often a time when pest populations can explode – particularly as many hitch a lift indoors from patio plants that are brought in. I am a big fan of “plant invigorator” sprays that combine minerals with dilute surfactants. These not only help boost plant immunity, but can act as physical deterrents to pests, without the need to deploy conventional pesticides.

Email James at james.wong@observer.co.uk or follow him on Twitter@Botanygeek

Contributor

James Wong

The GuardianTramp

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