Food and drink list
Age-old advice says never fertilize plants in fall or winter, but that was before artificial light. Don't feed plants that aren't getting enough light: this will encourage weak, straggly growth. Do feed those that are actively growing, following the schedule on the product's label. Many indoor gardeners apply one-quarter of the usual recommended dose of soluble, all-purpose fertilizer to all their plants at each watering throughout the winter. This provides enough fertilizer for plants growing under lights without harming those that are growing under weaker natural light.
How much water plants require during winter depends on their growing conditions. Many people assume they grow more slowly in winter and therefore need less water. But if the air is really dry, plants will transpire so heavily that they may require more water than they would in summer, whether they're noticeably growing or not. The usual watering strategy still works: wait until plants dry out slightly before watering thoroughly. Check them every three or four days; sink your finger into the soil to the second knuckle to see if it feels dry. If so, water until the excess runs into the saucer.
Some houseplants go completely dormant in winter. The most extreme cases are bulbs such as Jacobean lily (Sprekelia formosissima) and blood lily (Scadoxus multiflorus syn. Haemanthus multiflorus), which lose their leaves and may look dead. Just pull off any yellowed leaves and place plants in an out-of-the-way spot like a closet or basement until they show signs of life again, usually by mid- February. Amaryllis (Hippeastrum spp.) prefers a short dormant period; it usually awakens by late January.
Other plants don't visibly change but are still semi-dormant—Clivia, for example, prefers to be ignored until February or March. Stop watering in late November until you see flower buds, then start a regular watering schedule again.
Desert cacti (both the stubby, short ones, such as Mammillaria, Lobivia and Rebutia and the tall, candelabra ones, such as Cereus and Cleistocactus) are a special group: they like their winters cold and dry, with temperatures between 4 and 7°C. If you can maintain this temperature in a room with no light, don't water the cacti until late March. They'll shrink considerably but will plump right back up when you start watering them again. If ambient temperatures are warmer, such as 9 to 15°C, continue watering but only very lightly—perhaps once a month—since the plants are partially dormant. Cool, dry winter conditions mean heavy flowering come summer, so if your cacti have never bloomed for you, now you know why.
Photo: A bright pink cyclamen specimen. Photography by Aleksandra Szywala.