Margaret Lauterbach

Beware of mosquito refuges when gardening in containers and raised beds

Gardening in containers is close to gardening in raised beds; the major difference lies in the winter root temperature of plants. There’s less soil around plant roots in a container than in a raised bed, so any plant wintering over in a container will be subjected to lower soil temperatures than in a raised bed, and lower still than in the ground. In a container, figure on two zones colder than our usual.

There is one kind of container that I’ve begun to worry about for a different reason, that of Grow Boxes or Earth Boxes. They’re neat rectangular containers with a water reservoir from which plants are supposed to wick up moisture. These boxes are filled from a pipe at one end, but there is a gap opening about midbox that one can reach in to feel the water level. I understand a cover is available for that open gap, but it’s not well advertised.

The problem that I’m concerned about is that this water reservoir is a dandy nursery for mosquito larvae. Mosquitoes lay eggs in water, they hatch in one to three days, and then they live in that water from 7 to 13 days (depending on water temperature) before the mosquito emerges from that pupal stage. Mosquitoes are not only annoying, but they also can carry the West Nile virus (sometimes fatal in humans), and now another disease that has killed humans in the U.S., equine encephalitis.

We gardeners grow our own food to give ourselves and our families nutritious food free of unknown chemical contamination, so we should also be careful about other health threats we can control. Most gardeners I know are careful about eliminating standing water in their gardens and yards, such as disposing of old tires and other cupped objects that can hold water. If we’re to continue to use Grow or Earth boxes, we should at least invest in mosquito dunks that we can drop into the water to kill the larvae. When mosquitoes hatch in birdbaths, birds have a handy snack at hand, helping humans while they dine.

▪  I don’t keep a garden diary, but all gardeners should. My garden now is telling me that we had some very cool nights last spring or early summer. How is it telling me? Catfacing and interior bark-like columns in tomatoes, said to be caused by cool weather when pollinating, and by some biennial plants such as tronchuda, artichokes and cardoon going to blossom.

The Imperial Star artichoke was bred to yield artichokes their first year, so are usually grown as an annual. Other artichoke varieties grow and leaf out, but must wait for “vernalization” (cold weather) to stimulate them into budding and blossoming. Artichoke flower buds are the edible and choice part of the plant. If weather turns too cold, it kills these perennial plants, so vernalization and second year (and subsequent years) crops are only obtained in zone 7 climates.

Cardoons belong to the same species, Cynara cardunculus, but the plant looks quite different. Artichoke plants are upright, large thistle-like plants, while cardoons have large grandiose frond-like leaves. Cardoons are mainly grown as ornamentals, but they are edible. Custom today is that the leaf petioles of cardoon are blanched, sliced and steamed for table use, while artichokes are steamed or boiled for about 45 minutes, then the individual bud leaves are drawn through the teeth, and finally the “choke” (incipient flower) is removed, and its base (the heart) is eaten.

My first-year artichoke plants began yielding artichokes, telling me they had been cold enough to think they had gone through the required winter, but the artichokes were small and wimpy. But as I recently passed by a large cardoon, I noticed a very large “artichoke” on the top, nearly five inches in diameter. It was nearly time for lunch, so I harvested it and pressure cooked it. It tasted exactly like an artichoke to me. Now it’s producing others, so if it escapes frost damage, yum.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.