If you live north of the Tropic of Cancer, by the end of January, your houseplants will likely have started to emerge from their winter lethargy. If you look closely, you’ll probably see the buds starting to swell and some may have begun producing new leaves. This is due to the increase in day length, which has picked up from its low in late December (December 21 is the shortest day of the year in the Northern Hemisphere). In many areas, days are now a full hour longer than at Christmas.
These early signs of growth can push you to want to start fertilizing your houseplants. You probably stopped fertilizing in October or November, not wanting to encourage them to grow under the short days of winter and thus etiolate (produce weak, pale, stretchy growth), but now you’re brimming with enthusiasm and want to start “feeding” them. Is it time to start?
Close But No Cigar
Not quite! If you can curb your enthusiasm for just a few more weeks more, your plants will appreciate it. They’re still not getting top quality light and the days are still quite short. Fertilizing them now may cause exactly the kind of etiolated growth you want to prevent. It’s better not to encourage them quite yet.
By late February or early March, though, days in the North of the United States and the South of Canada will be about 90 minutes longer than today. That’s quite a jump! And full day length, that is, 12 hour days, begins on March 21 and that’s only 3 more weeks away. But already, when the day length increases to about 11 hours, the risk of etiolated growth is essentially gone and you can safely start fertilizing your plants. So, in most localities, the end of February or early March is a good time to start fertilizing again. That’s just a month away!
Of course, if you live between the Tropic of Cancer and the Tropic of Capricorn, the days never really get short enough to affect the growth of your plants and you can fertilize them all year long… but you already knew that, right?
How Long are Your Days?
If you want to know the day length in your town (remember it varies with latitude), the site Timeanddate.com can help you.