Check your magnolia trees for signs of scales

This is the time of year to check closely for magnolia scale, which can stress a magnolia tree and cause an overall thin condition.

The scale insect is about the size of a pencil eraser and is typically found on the underside of magnolia tree branches. As an adult, it does not move. However, gardeners often notice a black sooty mold that is a consequence of the scale before they notice the actual insect.

The mold is a fungus that grows on the clear, sticky honeydew that the scale insect exudes after feeding. The mold itself is not the real problem, but can be an indication of a scale infestation.

Such sooty mold also can grow on other types of trees and indicate problems with other insects.

On small magnolia trees, simply pick off any scale insects you spot and squash them. Other control measures may include spraying with summer-weight oil or applying an insecticide when the insect is in the active crawler stage, generally in early September, when it is most vulnerable.

For trees with a history of magnolia scale, applying dormant oil in late winter to early spring will provide good control. If your tree is affected, provide extra water during summer to minimize stress.

Now that vegetables are ripening, keep the following general rules in mind when you harvest.

First, it is important to harvest vegetables when they are at the peak of their flavor. Younger fruits often are more tender than those left on the plant longer. High temperatures hasten maturity. The length of time vegetables remain edible depends on weather conditions.

Handle vegetables carefully during harvest time. Check the garden daily and remove any ripe, damaged or misshapen fruits.

For fruits that are not easily removed from the plant, such as eggplant, cut the stem with a sharp knife.

Harvest on a regular basis to encourage production. Many plants, such as cucumber, okra and zucchini, will cease production if mature fruits are not harvested.

If you want to maximize the size of your dahlia flowers, keep the main stems free of side shoots, allowing only the terminal bud to develop. This results in one large flower per stem. This will be most effective when growing the large dinner-plate sized cultivars. Since the single flower will be heavy, the plants likely will need some support to prevent stems breaking from wind damage.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.