With gardens gradually going to sleep, I was thinking of ending my gardening columns for the season until I had a request from a reader who asked me to write about the care of house plants during the winter.

As with so many things, it is difficult to generalize about “house plants”. Obviously, there is neither an average plant nor an average house, but while there are some things that need to be considered under any circumstances anything I write here will have to be adjusted to your own conditions. But one word of advice: don’t change anything because I said so, just because I am considered the expert. If your plants are doing well, continue doing what you are doing. And don’t kill your plants with kindness. If they are being watered as needed and kept free of bugs, they can take care of themselves quite nicely.

All plants need light even though most plants we grow in our homes have been selected because they grow well in low or medium light conditions. Many of our house plants are “tropicals”, which means they come from a latitude where day length varies little from summer to winter. In summer, we may have to protect them from too much light while in the wintertime, we need to provide as much light as possible. That starts with cleaning windows and, if it is possible, removing mosquito screens once the summer bug season is over. Flowering plants and cacti should be moved as close to the windows as possible but avoid having the foliage touching cold windows.

If it is possible, supplemental light can be provided very successfully with grow light bulbs. Because there is a direct relation between temperature and light requirement, this is particularly important in rooms with higher temperatures, which means temperatures that are comfortable for us to live in.

 To give you an example: Every fall, I make cuttings from our geraniums and impatiens, root them and grow them on several windowsills in our house. We keep the downstairs rooms quite cool, around 15 C (59 F). The plants are quite happy without supplemental light, as long as I keep them on the dry side. But I have two shelves full of plants in my office, which is kept at 20 C to 21C (68F to 71F). Without supplemental light, the plants will grow lanky and useless for planting outdoors, so I have grow light bulbs on a timer above the plants that add 10 hours of extra light.

No matter where you grow your plants, it helps to turn them around occasionally to keep them from getting too lopsided because they are stretching towards the light. As for the ideal temperature, because most of our plants originate in tropical climates, they like an even temperature with the ideal range being 18C (65F) to 24C (25F) during the day and 15C (60F) to 18C (65F) during the night. What is more important than temperature is keeping plants out of drafts, either hot or cold. Don’t place them where they get hot drafts from hot air registers or cold drafts when an outside door opens. More on the subject of house plants next week.