Gardening

Should houseplants be fertilized over winter? The conventional advice is wrong.

Potted green plants on window sill indoors

Right on schedule after the frosts hit, the outdoor gardening questions stop and indoor plant concerns take center stage. It is officially winter in Alaska.

I have to tell you that I take these questions most seriously. Alaska is the only place in the nation I know of where residents travel a long way from former abodes and bring “memory plants” with them: A Christmas from a cutting of grandma’s old plant or one of dad’s favorite orchids or an amaryllis that has been in the family for generations. These become representatives of “the Old Country,” keeping some memories and connections to the Outside, alive.

Right at the top of the list of questions is whether to fertilize houseplants during the winter. Conventional advice has always been not to and comes with warnings that fertilizing in the winter can cause all manner of harm to plants. This advice is, for the most part, decidedly B.S.

First of all, let me make it clear that I understand a plant that is dormant doesn’t usually need fertilizer. The theory behind the no fertilizer in the winter rule is that all houseplants go dormant once we pass September. This, of course, is silly. First, in Alaska, good stewards of houseplants give their plants supplemental light — Right? Right! This means they do not go dormant and should be fed.

Second, there are lots of plants that are active even when their owners deprive them of light during the winter months. Take the so-called holiday cacti that produce their recognizable lovely flowers at Thanksgiving, Christmas or Easter. They actually shouldn’t be put under lights, as the natural changes in day length is what triggers them to blossom. And they occasionally need a bit of food as they are distinctly active. It takes nutrients to make those flowers.

Third, I think those who say not to fertilize in the winter are just repeating what their grandmothers told them. Where is the science? In my book — actually books; I have authored four best sellers so I am not making this up — plants are in control. They take up nutrients when they need them, not when you feed them. If they don’t need a particular nutrient, they don’t take it in.

Of course, my readers use organics and not chemicals and any advice to fertilize during the winter months is predicated on this use rather than chemical formulations. The fear of fertilizing in the winter is that you will “burn the roots” and strong chemical fertilizers are surely capable of damaging roots. Organic formulas are not chemically harsh and are designed to feed microbes which will then feed the plants if the plants need nutrients.

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The companion question is always and which fertilizer is best? There are lots and lots of brands of organic houseplant fertilizers that contain all manner of goodies for your plants ranging from kelp to soybean, compost to ground-up fish. Which to use? They all will work to some degree. Just make sure to read the labels. Do not buy anything that is not clearly organic. Kelp products contain necessary micronutrients. Compost products will add microbes as well as organics to your plants’ soils. Soybean and molasses based products are what many now use outdoors during the summer.

And, finally, big questions: When should you fertilize and how often? Once again, I point you to the label. Generally, if you follow the instructions listed, you can’t go wrong. Most important, your plants will let you know when they need feeding. Keep an eye on them and respond with a bit of food if leaves start to turn pale or yellow.

Jeff’s Alaska Garden Calendar:

Alaska Botanical Garden: Fall centerpiece workshop, in-service day camp and holiday wreath workshop are some of the wonderful activities lined up for you. Go to www.alaskabg.org

Holiday cacti: Do not put these under artificial light; natural light only.

Tree and shrubs: Do you have a long pole to knock heavy, wet snow off bending limbs to prevent them from snapping?

Jeff Lowenfels | Alaska gardening and growing

Jeff Lowenfels has written a weekly gardening column for the ADN for more than 45 years. His columns won the 2022 gold medal at the Garden Communicators International conference. He’s authored several books on organic gardening, and his latest book, "Teaming With Bacteria," is available on Amazon. Reach him at jefflowenfels@gmail.com.

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