Dear Helen: Please explain what 鈥渢rap鈥� crops are and what role they have in the garden.
C.L.
Trap crops are grown as decoys, or sacrificial plants, to draw pests away from plantings you wish to protect.
Plant pests will tend to go first for the most desirable, succulent food source they can find, as they operate under that universal principle: Life is short, and uncertain: Eat dessert first.
Nasturtiums are particularly appealing to aphids and also to the white cabbage butterflies that produce green worms on cabbage family vegetables. Planted with beans, especially broad beans, they will help to reduce aphid population in the beans. Some say that nasturtiums with yellow flowers are especially useful at attracting black aphids from broad beans.
Nasturtiums are similarly useful for planting among cabbage, broccoli, cauliflower, Brussels sprouts and kale plants for diverting aphids and cabbage butterflies away from these food crops.
Cabbage family plants are also targets of flea beetles and root flies (their larvae eat into the plant roots). Both pests can be diverted by clumps or rows of radishes, another attractive target of both pests.
When trap plants become heavily infested with pests, they can be pulled up and disposed of.
An issue that arises with trap plants is that they will become breeding grounds for pests; however, with dense pest populations come hungry pest predators 鈥� the beneficial insects that help to keep pest numbers down.
That is why plantings of flowers rich in pollen and nectar to feed beneficials are important adjuncts to trap crops. Sweet alyssum, cilantro, calendula, daisies and thymes are some of the best food sources for beneficial insects such as lady beetles, hover flies and parasitic wasps.
Dear Helen: How can I eliminate sowbugs from my greenhouse? They are under all the pots I use for tomatoes and in the boxes for growing vegetables.
N.C.
Sowbugs thrive and multiply most prolifically in the spring, in dark, moist conditions. Most of our spring, until recently, was dark, rainy and perfectly ideal for the creatures, though in our climate, you are bound to find them wherever wood meets damp soil.
Sowbug numbers will naturally decrease as temperatures warm and sunny weather becomes the norm. Do what you can to eliminate excess moisture in greenhouse soil. Consider raising the tomato pots up on cutwork bricks or openwork plant dollies.
Though its use outdoors should be very limited because it kills beneficial insects, diatomaceous earth could be used in the greenhouse to control sowbug numbers. The product, available under various brand names, acts on contact to dry up the insects.
GARDEN EVENTS
Dahlia meeting. The Victoria Dahlia Society will meet on Thursday at 7:30 p.m. in the main floor meeting room of The Victorian at McKenzie, 4000 Douglas St. The evening鈥檚 program will feature 鈥淭ips on Planting and Fertilizing your Dahlia Garden.鈥�
Plant sale. St. Michael and All Angels Church, 4733 West Saanich Rd. in Royal Oak, will hold a charity fundraiser plant sale on Saturday, from 10 a.m. to 1 p.m. The sale will offer flowering baskets and pots, tomatoes, dahlias, perennials, strawberry pots, and vegetable and annual transplants. Master gardeners will be on hand to help. There will be a food concession as well as a hall filled with garden items including tools, ceramic pots and more. Lots of gifts for Mom.
Plant sale. A Garden Babies for Birthright plant sale will be held on Saturday, from 9 a.m. to 1 p.m. at Our Lady of the Rosary Church, 798 Goldstream Ave. in Langford. This sale will feature flowers in cool shades of white, purple and blue as well as flowering shrubs, perennials, herbs and vegetable transplants. The sale is also known for its drought-tolerant and deer-resistant plants, all at irresistible prices.
Nature appreciation workshop. St. Michael and All Angels Church, 4733 West Saanich Rd., is hosting a 鈥淣ature Matters鈥� event on Thursday, May 10, 6 to 8:30 p.m., beginning with a half-hour social time with refreshments, followed by Scott Mair celebrating the sensory delights of nature walks and Pamela Greenthumbs helping everyone to plant an edible portable planter to take home. All supplies provided. Number of participants is limited. Reserve a place by calling 250-479-0540 or email [email protected]. Admission by donation.
