Do my houseplants need more light in winter?

Aug 25, 2023

Many of the plants kept indoors here in New Zealand grow wild in their native homes. The many varieties of philodendrons, for example, are native to the tropical Americas, a region that includes the Amazon rainforest in Brazil, where the average temperature remains around 25C all year round, with about 12 hours of canopy-filtered sunshine every day, and humidity at more than 70%.

This is why most indoor plants don't go dormant over winter, and why light and temperature are the biggest challenges for them during a typical New Zealand winter.

With so many different types of grow lights available now, it's much easier to artificially boost light levels over winter.

Grow lights mean there's no "bad place" for plants anymore. Linh Tong's main plant shelf in her Wellington home gets late afternoon sun in summer. Come winter, she supplements what little natural light they get by adding LED grow lights for the plants she can't move.

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"I keep an eye on changes in the direction and intensity of the sun in winter and shuffle some of my plants based on that," she says. I find some, like my ficus, philodendron and monstera, can tolerate direct sun in winter because it's less intense, and they keep growing right through the season."

A low-tech or no-tech approach is simply choosing plants tolerant of lower light levels. Leaf colour can be a good clue with darker green-leafed varieties coping better with lower light levels temporarily.

Keep in mind low light doesn't mean no light: If you can't read easily with the lights off, it's too dark for your plants.

It's tempting to shift plants closer to windows for more light over winter, but beware of cold windowsills at night.

Clean, clear windows make the most of the light you do get. A plant's leaves are like solar panels so give their leaves a good clean too. The layer of dust they accumulate over spring and summer can get in the way of photosynthesis in the lower light of winter.

As impressive as a glossy leaf looks, I stay away from most commercial leaf shine products. Many are comedogenic, leaving a waxy layer behind that can block stomata. There are some commercial brands such as Plant Runner that make organic, neem oil-based leaf shines that are non-comedogenic.

Plain water can do the job too. I often use makeup wipes for my little-leafed houseplants. Bigger-leafed ficus and peace lilies get washed down with warm water in the shower. African violets, and other furry and spiky leafed plants get "dry cleaned" with a small, soft brush.

Some plants like orchids and begonias are more prone to leaf and stem rot if water is left sitting on leaves or in crevices, especially in winter when leaves take longer to dry. Rather than spray them directly, I apply leaf cleaner to a microfibre cloth or cotton pad and gently wipe them down.

For water spotting that won't budge, my home remedy is a lemon: Lemon juice helps dissolve water spots. I use one tablespoon of lemon juice mixed with two cups of water.

Aucklander Anna Gervai runs an online one-stop-shop for houseplant hobbyists (lovethatleaf.co.nz). She juggles running her business with caring for her plants.