Ask a Master Gardener: How do I get rid of wasps, yellow jackets?


Question: They're back, those pesky wasps and yellow jackets. What can I do?

Answer: First, make sure those are wasps and yellow jackets you're seeing, and not bees. Just as bees give us honey and pollination, those wasps and yellow jackets also do us good: they prey on garden pests. So unless they are a serious nuisance or danger, try to leave them alone.

There are a few things you can do. Leave no food for them to eat. Cover trash cans tightly. Clean up ripe fruit around the yard. Red or yellow clothing, and some perfumes, attract wasps and yellow jackets.

Destroying nests can be dangerous, as these insects have barbless stingers, and can sting repeatedly, unlike bees. Begin watching for nests early in the spring, as smaller nests are easier and safer to deal with.

Wait until after dark and wear protective clothing. Spray aerial nests with a formulation of pyrethrum. If this all seems a bit too much, you can buy commercial wasp traps.

Wasps and yellow jackets die in winter, except for the fertilized queens, which overwinter in bark and leaf litter. Each one you can locate and kill eliminates a potential nest. You can lure the queens to a simple trap made from a mixture of sugar and soapy water in a pan.

Q: Someone told me that some of my plants are bolting. What does that mean, and why does it happen?

A: Bolting is a word used by gardeners to describe the flowering of a plant. It most often happens with plants grown for their foliage, like lettuce, spinach and Chinese cabbage. However, it also can happen to basil, parsley, celery, onions or broccoli.

Bolting is a normal part of a plant's life. It's how it sets seeds and perpetuates the species. However, it is quite undesirable from a gardener's point of view, as it turns the edible part of the plants bitter, as well as produces flowers, which though pretty aren't what the gardener had in mind. With onions, it keeps the bulb from developing.

Environmental factors cause bolting. Hot weather causes lettuce and spinach to bolt, but cold spring weather makes celery flower. Alternating hot and cold weather promotes bolting in onions and Chinese cabbage. Drought or insect problems also can cause bolting.

Cool weather plants do best in spring. Don't try to grow lettuce or spinach in the hot summer months. If timed right (and seed packets can help you there) you can minimize your bolting problems. And if some plant does bolt and you have chickens, be sure to feed it to them. They love those little flowers!

Q: I start plants from seed in my greenhouse, and although I sterilize garden soil in my oven for use as potting soil, I still have a problem with fungus gnats. What can I do?

A: Fungus gnat adults are a type of fly, and though annoying, don't do your plants any harm. However, their maggots can damage the roots of plants. Fungus gnats live in manure and decaying vegetable matter, so potting soil rich in humus can harbor them. If you pasteurize your soil between 140 and 180 degrees for 30 minutes, that should take care of them. Still, you might have a problem in the summer, as the flies are only 1/10 of an inch long, and can slip through almost any screen. If you see fungus gnats on your plants, kill the maggots by letting the soil dry out as much as possible without harming the plants.

Q: I've often seen the word "cultivar" used when identifying plants. What does it mean?

A: Quite simply, the word cultivar means a plant that's been cultivated, as opposed to grown from natural or original plants that originated in the wild. Cultivars can be the result of selection or hybridization; they rarely survive more than two generations outside the garden. They also are almost impossible for a gardener to reproduce, as they revert to the more original form when planted from any seed they produce.


Master Gardener Kathleen Bander is a resident of Bellingham and life-long gardener. For more information on Whatcom County Master Gardeners, go to

Ask a Master Gardener will appear in The Bellingham Herald weekly through July. If you have a gardening question you'd like answered in the column, please email it to

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