, Salem, MA

November 22, 2013

Column: When unwanted pests come in with your plants

North Shore Gardener
Barbara Barger

---- — Q: All of a sudden there are little white things flying around my plants. I never had them before, but I think maybe they came in with the plants I had outside all summer — or maybe a new plant I bought in December that was very wet when it came. What could they be — maybe white flies? But they seem to be staying closer to the dirt.

A: Could be either! Use a soap spray to get rid of them. The real trick to getting rid of white flies is to be persistent with the spraying. Repeat every week to 10 days, and there will be a better chance of killing each generation as it hatches. If you don’t get rid of them, you’ll see leaves begin to yellow and drop — and the plant will die. You will see them fly any time you disturb the plant — shake gently or brush by and you’ll set off a cloud of the tiny pests.

Fungus gnats are common in plants that were outside — they thrive in rich, moist soil. The gnats live by eating the plant roots, so you do need to get rid of them for that reason — and for esthetic reasons!

The same soap spray that you use for white flies will help. Use it as a ground soak. But easier still is to place a half-inch layer of dry sand over the top of soil in the pot. Sand will keep the soil surface drier, and the tiny bugs won’t be able to reproduce as rapidly, as you’ve changed their ideal living conditions.

Q: I have a basil plant (started from seed last spring, of course!) that has grown into a small bush. It’s still outside (in a pot, not the garden) and I’m wondering, can I bring it in and winter it over? I did that with a pepper plant one year and was eating peppers earlier than ever the next year!

A: Hope you’ve rescued the basil — it’s at the end of this year’s growing season, and unless you have a place for it on a very sunny window, it may be lost. But since you were able to keep a pepper plant last year — and even produce pepper — I’m pretty sure that the big basil will make it!

Grow it with all the needs of the pepper: lots of sun, decent humidity. Fertilize and watch for small bugs. The bugs can be removed by blasts of cold water in the sink or a soap spray that is safe for use on eatables.

Prune basil as you use it, or snip it and freeze it in ice cube trays so you can use small portions in soups and salad dressing and pesto — that’s all there is to it. Some species, even in our cold climate, will appear to come back in the spring. These are not perennial but rather self-seeding in a well-mulched, well-protected spot in your spring garden — a nice spring surprise.

Q: I do read your column, not religiously, but often. (Lack of time, not interest!) I read the recent one on keeping fig trees alive. In my experience, derived from my father, Louis Rossi, and his brother, my uncle, Giovanni Rossi, I have found that you can keep a fig tree alive outdoors by doing some of the things you mentioned, but if you want fruit, you have to do much more!

A: My barber, who lives in Gloucester, mentioned that he has a fig tree and he tried everything — covering it with leaves, wrapping it, etc. — but he never got figs! I told him to wait until the leaves fall but before heavy frost. Then, tie the branches together as tightly as possible with rope, as if he were to dig it up and move it. Fig branches are fairly supple. Then, dig on the front side and back side cutting all the roots, but do not disturb the roots on the sides. Next, dig a hole on the front side large enough to tip the tree into the hole so that the entire top of the tree is down to about ground level. When the tree is now nestled in the hole that you have dug, cover it with plywood and place the excavated soil over the plywood to prevent the frost from penetrating downward. The earth temp keeps the tree from freezing.

In the spring, after danger of frost, dig the tree up and stand it up as if it were in its normal position.

My barber did this, and now he gets lots of figs! Just my thoughts on that issue ...

Q: I have two geranium plants that have been outside all summer. One is a deep red that I love. I have never been successful in bringing geraniums in to winter over. They always turn brown and die no matter how carefully I try to acclimate them to the house. How easy is it to start a new plant from the main plant? Is it better to put the cutting in water or to dip it in rooting powder? I really hate the thought of losing the deep red one.

A: Move the colors you want to keep indoors on the sunniest window possible before a hard freeze and grow them as any houseplant. Water as needed, and the new growth will be visible almost immediately.

About the end of December, it will be time to take cuttings of the healthiest of this growth from the old plant. Cut pieces about 6 inches long. Prepare pots of potting soil. If you have sand or perlite available, mix in a few spoonfuls per pot. This lighter soil will make it easier for new roots to form.

Q: I have a small azalea that has white on all of its leaves ... I had transplanted the bush last year — never had it before ... it almost looks like a coating, but is easily “wiped off” with a finger. Would you know what this is and should I be concerned, or do/buy anything to treat it?

A: Your azalea bush has powdery mildew which probably won’t hurt the plant. Mildew does hurt the plant if it blocks sunlight from reaching the leaves and prevents photosynthesis, which is food for the plant to grow — the black sooty mildew is far more serious than the gray/white mildew for that reason!

As to why you never had it before, it could have been caused by several things. You transplanted the azalea this year, and you may have changed the air circulation around the plant. Also, mold spores might have been living in the new planting area, just waiting for a new host plant.

If the appearance bothers you, you can probably wash it off with a hard stream of water or there are plenty of fungicides at the garden supply stores. Some gardeners swear by just baking soda and water as a foliar spray for mildew.

This late in the season, I wouldn’t bother with it. You might want to keep these suggestions for next year, though.

This week’s dirt: Look under the leaves for some free plants.

As you’re raking the last leaves, take a minute — stop to dig that last flowering annual from the garden and put it in a pot and bring it indoors to a bright windowsill — but do it today.

It could be a dwarf marigold, an impatiens, a coleus, even some pretty weed — it doesn’t have to be a flower, it can be a veggie — a small cabbage, or an herb would welcome a warm windowsill for a few months.

By now, the plants may have had some cold damage — and won’t live forever — but it’s a free houseplant for you and the kids and will supply some color in the late fall.