- by Roberta Brignell and Jackie Campbell

Another gardening season is over, but we can rely on a wide variety of beautiful houseplants to keep us going over the long winter. Here are a few tips on selecting houseplants and typical problems and treatments.

“How do I choose the right plants? “ There are many nurseries and stores that have indoor houseplants for you to explore for different foliage, color and size. Your local library is an excellent source for researching the different plants for your home.

Ask a Master Gardener for assistance! In Grey & Bruce counties email [email protected]. For other communities in Ontario, click on this link to find a Master Gardener www.mgoi.ca/groups.html.

When purchasing a new houseplant, remember that your first task is to select plants that can best withstand the particular conditions inside your home. It's easier to purchase a plant requiring the same environmental conditions your residence has to offer than to alter the environment of your home or office to suit the plants. Pay particular attention to the plant’s light requirement. To be assured that the plant you buy is healthy, check the undersides of the foliage and the axils of leaves for signs of insects or disease. Select plants which appear to be free of insects and diseases, show healthy foliage. Avoid those having yellow leaves, brown leaf margins, wilted foliage, spots or blotches or spindly growth.

Light, water, temperature, humidity, ventilation, fertilization, and soil are the chief factors affecting plant growth. Too much or too little of any one of these factors will prevent a plant from growing properly indoors. Light is probably the most critical factor for house plant growth. Houseplants can be classified according to their light intensity requirements. For example –high (meaning direct light), medium (Indirect light) or low (a few feet back from the light).

"How often should I water my plants?" The plant itself will tell you. When it's too dry, a plant wilts and turns gray-green; when too wet, it drops leaves or turns yellow. Avoid both of these extremes. Plants should not be watered on a schedule, but watered when they need it. Factors influencing plant watering include differences in potting media, humidity, temperature, and pot type. To test a plant for watering, you must feel the soil at the root zone. Because a plant's roots are usually in the bottom two-thirds of the pot, it doesn't need water until the bottom two-thirds dries out slightly. (If your finger can't penetrate 5 cm deep, you may need a more porous soil mix or the plant may have become root bound) Another quick test is to lift the plant to check its weight change, caused by changes in soil moisture. Water should be at room temperature. Rainwater, distilled water and most tap water is suitable for plants. Avoid water that is either very hard or very soft and never use chlorinated or chemically softened water. Some plants require different water practices to assure good health.

“ How often should I fertilize my plants?” The goal in growing indoor plants is maintenance. Large amounts of fertilizer are therefore unnecessary for most indoor plants. Commercial fertilizers used for indoor plants are sold in granular, crystalline, liquid, stick and tablet forms. Most common fertilizers are water-soluble. During the winter months, houseplants don't need fertilizer because reduced light and temperature result in reduced growth. Fertilizing at this time could harm some plants. Monthly applications of a dilute liquid fertilizer in the summer months will keep most plants healthy. Excessive fertilizer results in the buildup of salts and excessive, leggy growth.

“Can plants adapt to indoor temperature changes?” Excessively low or high temperatures may stop growth, cause a spindly appearance, foliage damage, leaf drop or plant failure. However, most houseplants tolerate normal temperature fluctuations. In general, foliage houseplants grow best between 20°C and 27°C during the day and from 15° to 20°C at night. Most flowering houseplants prefer the same daytime range but grow best at nighttime temperatures of 13° to 16°C. A good rule of thumb is to keep the night temperature 5 to 10°C lower than the day temperature. Indoor plants, especially flowering varieties, are sensitive to drafts or heat from registers. Protect them from sudden, brief changes in temperature. Do not locate your houseplants near heat sources. Temperatures on windowsills in the winter can drop to dangerously cold levels. Curtains or blinds can cut off the heat from the room and plants on the sill could freeze.

So give a houseplant a try over the winter. You may really enjoy the experience!

Controlling Common Houseplant Pests
Non chemical controls are often adequate to deal with moderate infestations of insects. While houseplants are not included in the Ontario pesticide ban, we have opted to show only organic control methods. Should you choose to use chemical pesticides we suggest that they be limited to highly valued specimens; also, read the labels carefully to ensure the product applies specifically to the pest and follow the directions provided.

Washing and/or pruning can be effective methods of dealing with all the pests noted below.
Washing: Using a soft cloth dipped in a mild detergent solution (1/2 tsp per litre of lukewarm water), wipe insects off plants with smooth leaves. You can also dislodge pests with a forceful spray of lukewarm water.
Pruning: Cut off the branches where the infestation is worst. This will make it easier to control pests on the rest of the plant and, if the infestation is isolated, pruning may be all that is required. ¹

“Do I ever just give up?” When a houseplant is heavily infested and badly damaged, the best course of action is to throw the plant away. Minimize your losses and avoid exposing other plants to the same pest problem. If you are reluctant to discard the plant, prune it practically to the soil. If it resprouts, watch new growth carefully for signs of infestation.

References:
¹http://www.extension.umn.edu/garden/insects/find/houseplant-insect-control/
²https://plantsstories.wordpress.com/2009/04/19/updates-pest-control-vitex-trifolia-mulberry-cuttings-red-spider-mites/
³https://extension.umd.edu/hgic/mealybugs-houseplants
⁴https://extension.umd.edu/hgic/scale-insects-houseplants
⁵https://www.planetnatural.com/pest-problem-solver/houseplant-pests/whitefly-control/