There's still time to plant zucchini

Q: Every year I plant zucchini, and every year I have the same problem arise with them. After a month or so of growing, I notice that the stems seem to start rotting right where they come out of the ground. After a few weeks of this, the plant dies. What could cause this, and how do I fix it?

A: What you call stem rot may be the work of squash vine borers. Squash borers pierce the stem and lay their eggs in it, causing the plant to wilt and later become mushy. This happens at ground level early in the season and can be discouraged by wrapping young stems in aluminum foil to protect them from adult borers. If you see wilting, slit open the stems and remove the larvae (white with black heads). Next, cover the damaged stem with good soil and keep it watered. New roots will develop from the buried stem.

During the spring, it helps to keep young plants covered with a floating row cover (available at nurseries and garden centers), pegged down at the edges so flying adults cannot enter. When the flowers start to open, you must remove the row cover to allow pollinators to enter. By that time, the stems are usually hard enough that the insects cannot penetrate them to lay their eggs.

You may also try staggering the planting. Plant a second crop of zucchini in early July, when the borers are less active.

Q: I have several tall sedum plants that have been established for about 10 years. They seem to grow healthy each year until late summer/early fall. When they begin to bloom, the center of the plant falls. It looks like something was nesting in the middle of the plant, but that is not the case.

A; After several years, the center of sedum plants will show signs of dying out. At this point, you must divide the plant in order to keep it vigorous. You can divide sedums in spring or after they have bloomed in fall. Sedums do not like wet feet. In fact, too much water, as well as fertilizer, can cause flopping.

If you are growing Autumn Joy sedum, note that it tends to get tall and floppy, even when new in the garden. To prevent this, try pinching or pruning the plant. When it gets to be about 8 inches tall, usually around June, cut it back about 4 inches. It will still bloom, but be less likely to split open in the fall.

Q: We have a red raspberry plant that is about 8 years old and is fairly small. It flowers but produces little to no fruit, and the fruit is very small. The flowering stops and starts throughout June, July, August and September.

It is not trellised and I'm not sure how to prune it due to not knowing if it is considered summer bearing or everbearing. How do I determine this? The canes reach about 30 inches, and they fall over. It comes back every year, but we would like it to produce more fruit.

A: The crowns and roots of raspberry plants are perennial, but the individual canes are biennial, that is, they are vegetative the first year, bear fruit the next, but then die at the end of that year. This may be one reason they don't produce fruit all the time; the raspberries could be producing their vegetative canes and will bear fruit next season. Each spring, the plants produce canes (suckers) from buds on the crown and on underground lateral stems. It's easy to tell first-year canes from second-year canes. First-year canes have green stems, while second-year canes have a thin, brown bark covering them.

There are two categories for raspberry plants:

• Summer bearing raspberries provide one large harvest, usually in late summer or early fall. Summer bearing raspberries bear fruit on two-year old canes, that is, the canes that sprouted last season.

• Everbearing raspberries generally have two harvests per season; one in mid-late summer and one in the fall. The fall crop is usually a bit lighter and is on one-year old canes of the current season.

Raspberries must be pruned every year in order to produce a good crop, increase air circulation within the bushes and reduce incidences of disease. Since raspberry roots and crowns are perennial, you must only prune the canes. Both types must be pruned when they are still dormant. The best time to prune raspberries is before the buds swell, usually between February 15 and April 1 in northern Illinois. For summer-bearing types, the two-year-old cane that bore fruit must be pruned immediately after harvest.

For more information on cultivating raspberries, read this article from the University of Illinois Extension: http://web.extension.uiuc.edu/macon/palette/080706.html

• Provided by Mary Boldan. Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, open 9 a.m. to noon on Monday, Wednesday, Friday and Saturday. Call (847) 298-3502 or email Cookcountymg.com@gmail.com.