Water — too much or too little — is what kills most houseplants.
I recently visited my friend Alicia Jenks of Green Dragon Farm in Weathersfield, Vermont, to take a look at her houseplants — some 50 or more of them. Alicia considers them her “indoor garden," her plant friends that keep her gardening all winter. She doesn’t think houseplants are hard to maintain, but asserts, “You have to pay attention to them. They can’t take care of themselves.” Good point.
Alicia does not put her houseplants outside in the summer. Instead she keeps them on a covered screen porch. This allows her to regulate how much water they get, keeps them away from pests like earwigs, and keeps them from getting sun scald.
Before she brings them into the house in September, Alicia gives her houseplants a good gentle shower — outdoors, with a hose. Aphids and other pests can often be knocked off with a stream of water, avoiding the need to use a soap solution to kill them later. Of course, you must get the underside of leaves, too, and rinse the surface of the potting soil as well.
Alicia keeps her best, most luscious houseplants in the living-dining area. Her junior varsity team she keeps upstairs in a spare room. The rest, the club squad, stay in the basement under lights. She gives each the same care and any plant can get upgraded to the living room. All it needs to do is bloom.
Water — too much or too little — is what kills most houseplants. Alicia does not follow a set schedule such as watering every Sunday, though that works for many people. Instead, she regularly checks her plants by placing a finger on the soil surface. If it is lightly moist, she does not water. If it is dry, or if the leaves are losing some of their turgidity and wilting, she waters.
Alicia gives a deep watering each time she waters, enough so that a little water will seep through the pot’s holes in the bottom and into the saucer it sits on. In the summer — when it is hot — she might have to water some plants every two to three days. In winter, once a week may be enough.
What about fertilizer? Alicia gives some liquid fish emulsion fertilizer once a month from April to September. Fish or seaweed fertilizers are good for houseplants because they have a wide variety of nutrients, including many micro-nutrients that are not found in chemical fertilizers. During the winter, most plants are not growing much and should not be fertilized, she told me.
Most houseplants do not need much direct sun. Before you buy a houseplant, read the tag to see what it needs. Bright indoor sunlight is fine for most plants. Cyclamen, begonias, Christmas cactus, poinsettias, oxalis and many others will do well in a brightly lit room, without direct sunshine.
I have read that the direct sunshine diminishes exponentially with the distance from the glass. That means that sunshine two feet from the glass is four times weaker than sunshine a foot from the window, and at three feet away, it is nine times weaker. Keep that in mind when you place a plant. Rosemary — which appreciates strong sun — should be as near the window as possible without touching it. No plant leaves should touch the glass in winter.
Books and websites are full of advice. Still, I find the very best information about houseplants is found in my 1969 edition of Thalassa Cruso’s book, "Making Things Grow: A Practical Guide for the Indoor Gardener." Although this book was written nearly 50 years ago and is long out of print, I have never visited a used bookstore that didn’t have it. And it is available online.
What I like about Cruso’s book is the practical nature of it. It covers pretty much any houseplant you can buy. She has grown it, figured out what makes it happy, and will save you the trouble of experimenting — and killing — houseplants yourself. Plus, her writing is easy to follow — and sweet.
Success is often in the details. Take those bright red zonal geraniums we often grow in pots in summer to adorn a sunny location. Did you know that they do best when their potting mixture is well patted down in the pot, compressing it? I didn’t. Or that geraniums can be made to flower beautifully indoors in winter by pinching them back regularly in summer, frustrating their attempts to blossom until winter? Cruso taught me that.
Alicia does not re-pot her plants very often. She believes that many bloom better if the roots are a little crowded, but if the roots are pushing out the top or through the drainage hole, it might be necessary.
Cruso warns against “potting on" a root-bound plant into a much larger pot. She explains that using a pot more than an inch in diameter larger than the pot a plant is growing in can cause root rot. Why? The excess soil material will not easily dry out — because the roots will not reach it.
I never think of myself as a houseplant kind of guy, though when I counted up my houseplants for this article I saw I had 43 plants, including a Crown of Thorns that is more than 100 years old, a banana tree, a fig, an eight-foot hibiscus and an even bigger frangipane tree that bloomed all last winter!
— Henry Homeyer's blog appears twice a week at dailyuv.com/gardeningguy. Write to him at P.O. Box 364, Cornish Flat, NH 03746. Please include a self-addressed stamped envelope if you wish a mailed response. Or email email@example.com.