Indoor gardening primer

TORONTO, ON - SEPTEMBER, 20 Mark and Ben (his son) Cullen are seen in the Star studio for logo photos. The two will be co-writing the weekly Urban Growth column in Homes & Condos. September, 20 2017

by Mark and Ben Cullen

Dirty knees and gardening go together, just not at this time of year. Fact is, many of us ‘garden’ indoors in the Canadian winter.

We grow tropical plants, amaryllis, windowsill herbs, bean sprouts and more.

The need to nurture plants through the winter months is a good thing. There is nothing like getting some real dirt under your finger nails.

Here is our primer for mid-winter gardening success:

  1. Low light = poor performance. Most tropical plants need sunlight to perform and grow well. The hibiscus that you brought indoors from the patio this fall is looking tired and unhappy about now. Hibiscus, like many flowering tropical plants prefer high light. This is true for oleander, mandevilla vine, fig trees and citrus trees.

    The answer is to give your tropical sun-lover as much light as possible by placing it in a south or west facing window. However, that window receives about 500 foot candles of light on a sunny day this time of year, while in June the same window receives about 2,500 foot candles.
    Before you consider moving closer to the equator, cut the plant back. Mid-winter is the perfect time of year to prune large tropical plants. Pruning thickens and enhances the appearance of the plant. By early May, your tropical plant will be pushing new growth that will explode in the warm early summer temperatures and sunshine.
  2. Less water. As your indoor plants slow down their need for water is reduced. A bit like us, when we are most active, we need to hydrate more often. As a rule of thumb, water indoor plants thoroughly only when the soil is dry about 2 to 3 centimeters below the surface.
  3. Tepid water. Plants are like people and they don’t like cold water. Ever take a cold shower? Didn’t think so. Pour water into a large container before you go to bed and use that the next day to hydrate your thirsty plants. Gardeners using municipal water need to do this to let the fluoride and chlorine dissipate in the form of gas over night. If you use water right from the tap chances are good that a calcium deposit will build up around the root zone of your plants. You see evidence of this on clay pots when a white, powdery substance appears on the outside of the pot.
  4. Air dry? = white fly. One of the most frequent questions we get this time of year on our website is, “How do I get rid of white fly on my indoor plants?” and the answer is … well there is no easy answer. White flies are stubborn and once they find their way into your home there is no easy way to get rid of them. Yellow, sticky traps are quite effective at bringing them under control, but seldom eliminate the problem. Daily misting with a spray atomiser also helps to minimize the problem, as white flies hate water and love the dry atmosphere of a Canadian home mid-winter.
  5. Re-pot. If you have an indoor plant that is languishing, now is an appropriate time to pot it up into a larger sized container. First, pull the plant out of its existing pot and examine the roots. If they are ‘hitting the wall’ of the pot and twirling round in circles that is a sign that the plant is under stress.

    After you have removed the root mass from the existing pot, pull the roots apart. Get violent, pulling and tearing up to 30% of existing roots to break the root mass free. When it discovers new soil in a clean pot it will begin putting down new roots.

    Pot up one size when re-potting (from an eight inch to a 10 inch pot) and use quality, new plant soil like Pro Mix.

    After the plant is in its new home, compact the soil around the roots with a wooden ruler or similar piece of wood. Push air pockets out, which can trap water and cause root rot.

    Water thoroughly and don’t begin to fertilize until new growth appears on the top portion of the plant.

    Finally, keep the foliage of your tropical plants dust free. Use insecticidal soap on a dampened, clean cloth to wipe down dracaena, yucca, scheflerra and virtually all leafy plants.

    Happy plants, happy home.

    And you thought you had the winter off.

    Mark Cullen is an expert gardener, author, broadcaster, tree advocate and holds the Order of Canada. His son Ben is a fourth-generation urban gardener and graduate of University of Guelph and Dalhousie University in Halifax. Follow them at, @markcullengardening, on Facebook and bi-weekly on Global TV’s National Morning Show.