Grow It In Maine

White fly

Thu, 02/11/2016 - 9:30am

My house plants are okay,” Carol said. “But my hibiscus isn’t doing so well. I’ve kept it away from the others. It has lots of tiny insects with white wings on the leaves or flying around it. What are they?”

They’re white flies. They are likely to appear in January and February. They can’t hurt you but you don’t need them. Here’s the story:

To sprout and grow in soil, most plants use the chemical elements nitrogen (N), phosphorus (P) and potassium. A fourth soil element is magnesium (Mg), used or needed in a smaller quantity. From now on, plants should have begun to rise from dormancy and grow again in the increased sunlight.

Magnesium is in the soil used to pot up indoor plants. It’s soluble in water and after a while, it begins to leach out with repeated watering. A few white flies emerge – as mysteriously as people pick up the germs of the common cold. Certain potted plants attract them, such as hibiscus. Those white flies hatch, go through five forms as they grow, and within weeks, reach adult-hood, ready to mate and begin the next generation.

To reduce that population and help fertilize the plant (or plants), begin watering your house plants with a solution of Epsom salts – maybe a teaspoonful to a half gallon of water, every two weeks. (If one uses fertilizer, add it.) The white flies could dwindle. The magnesium in the Epsom salts acts as a systemic insecticide. Those five forms of growth (known as instars) are not all affected by single treatments, but the magnesium seems to work. One could tweak this formula if needed.

Most house plants are waking up now. I like to stand some of these in the shower so that we bathe together – but not in very hot water. Furry-leaved plants like African violets or streptocarpus (aka Cape Primrose) don’t need this treatment. The plants drain in the shower while I dress.

If any need shaping, begin pruning next week.