COLUMN: Examining indoor tropics

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You have battened down the hatches in your garden and waved goodbye to the season.  Time to sit down and read a good book. Not so fast. Remember the tropical plants that you brought indoors in the fall? The hibiscus, oleander, mandevilla vine, and the herbs that are now dropping leaves on your living room floor? They could use some TLC right about now. Here is why.

You'll notice that as the temperatures out of doors fall so does the humidity in your home, condo, or apartment. Seeing as we share the same indoor air as our tropical plants, it is important to remember that most of them come from a warm, southern place. In other words, their native habitat is quite the opposite of your current home environment. Your aspidistra is wheezing and inhaling hard, you just can’t hear it.

The first thing that you should do is wipe down the leaves of your broad-leafed plants using insecticidal soap, which is more soap than insecticide. In other words don’t worry that you are exposing your hands to some toxic substance. Spray some on a clean cloth and wipe down the leaves of your plants while watching a TV show that does not demand your full attention. In my experience this would include all of them, except maybe Jeopardy. You really have to concentrate to get the full benefit of Jeopardy. Wipe both sides of the leaves thoroughly to remove dust and grime.

Small-leafed plants, like the famous ficus benjamina or ‘Weeping Fig’ [so named as it really is not very happy in Canadian homes during our winter months], can be cleaned by simply spraying the leaves with the insecticidal soap solution, top and bottom.


Indoor plants are losing their leaves

Think, once again, about the natural habitat of your Dumb Cane [dieffenbachia]. Warm. Humid. Near the equator where there is lots of light.

It is natural for most indoor tropical plants to lose some leaves this time of year, especially if you had them outside for the summer. The intensity of natural light in our homes right now is very low. A south-facing window in the summer may be exposed to up to 2,500 foot candles of light on an average summer day. The same window this time of year meets about 500 foot candles. Is it any wonder that we sleep longer in winter than summer? And it is not just the day length that causes the sun to lose power in winter, it is the low angle at which the sun sits when it does shine. The shortest day of the year, Dec. 21, is less than two weeks away. Shortly after this day is when ancient Druid priests, using a golden sickle, would cut mistletoe from a holy oak tree. Delivering it to the people, the mistletoe was hung in the house to ensure fertility, bring about love, and ward off witchcraft.

While Druids cut mistletoe, your hibiscus is losing its leaves. Don’t be alarmed by this as the tree/shrub needs to lose leaves in order to rejuvenate itself. I cut my leafy tropicals back this time of year by at least a third. Don’t give them a bowl cut: reach into the body of the plant and remove some of the woody, less leafy growth with a sharp pair of hand pruners. This will encourage more growth from the middle portion of the plant, producing a thick, healthy appearance and more even flowering, in the case of the hibiscus. 



Generally I don’t fertilize my tropical plants this time of year. They are not growing as they did in the summer, so they have no need for the ‘nutrients’ or fertilizer. An exception is the African violet, which grows more or less year round. I fertilize them with half strength 20-20-20 water soluble fertilizer every two to three weeks all year round. 



A tropical plant has its own way of telling you whether or not you need to re-pot it. Look for roots that are growing through the surface of the soil.  If they are not obvious to the naked eye then scratch the soil with your fingers to see if they lurk just beneath the soil's surface. Ah ha! There they are. Now tip your plant on its side and look for roots growing out of the drainage holes in the bottom of the pot.  If you don’t see them making an escape, feel through the drainage hole. If you find roots, your plant is telling you that it is time for either a bigger home or that it needs its roots pruned. 

If you choose to re-pot your indoor plant, be prepared to make a mess — a drop sheet is called for if you are going to do this indoors. Pull the plant out of the pot, roots and all. It is silly to think that you have to be gentle while doing this as, chances are, it is stuck in there, the roots making pressure against the inside wall of the pot in their effort to get out.  For a large tropical plant this could be a two-person job. No worries, you can’t hurt the plant.

Once released from its undersized pot, pull the roots of the plant apart and be ruthless in doing so. A pair of scissors may be called for, or, a small, sharp kitchen knife. The idea is to give the roots freedom and convince them that it is indeed time to create new ones: to put roots down into a new home. You are pruning the roots as you would prune the top portion of the plant and for similar reasons: to thicken them and encourage new growth.

When choosing a new pot, only go up one size. A 10-inch pot calls for a clean 12-inch.  An 18-inch pot calls for a 20-inch or so.

I favour clay pots over plastic as I swear that plants perform better in them overall. But then, that could be in my head. I do, however, know that clay breathes through every pore, while plastic does not breathe.   

Be sure not to buy cheap, poor quality potting soil. Look for a quality mix that is weedless, light, open and one that does not contain nutrients. Many of the potting mixes created for summer containers contain a slow release fertilizer, which is well and good, but not for your valuable indoor tropicals that need a rest after the trauma of re-potting.  A good, gentle watering after the re-potting exercise is over is all that is needed.  


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Mark Cullen is Canada’s best-known gardening broadcaster and writer. He is the spokesperson for Home Hardware Lawn and Garden. Sign up for his free monthly newsletter at and watch him Wednesday mornings on Canada AM. His column, which focuses on our growing zone, appears in the Hants Journal every two weeks.






Organizations: Canada AM, Hants Journal

Geographic location: Canada, Hants County

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