Reduce pest problems by rotating vegetable crops

The easiest way to reduce pest problems and avoid using chemical controls in the vegetable garden is to rotate crops. Many insects and diseases attack a number of related vegetables within the same plant family. By planting vegetables from a different family in a problem area each year, you minimize the chances of a repeat infection.

The basic vegetable families are the cabbage family (broccoli, cabbage, cauliflower, brussels sprouts, radishes and turnips); the cucumber family (gourds, melons, squashes and cucumbers); the nightshade family (eggplant, potatoes, tomatoes and peppers); the goosefoot family (spinach, beets and chard); the onion family (leeks, garlic and onions); the legume family (all peas and beans); and a family that includes carrots, celery and parsnips.

Make sure there is at least one drainage hole in any container you use for seasonal plantings. It is not necessary to use a layer of gravel in the bottom of the container. Fill the container with a lightweight, fast-draining soilless potting mix. Avoid using heavy garden soil, even if you amend it with compost.

Leave at least 1 inch between the top of the growing medium and the lip of the pot to allow some water to accumulate and soak in. Allow 10 to 12 inches of potting mix depth for plants' roots. Very large containers can be partially filled with wood chips, plastic bags filled with packing peanuts or empty plastic pots turned upside down to conserve soilless mix. Separate the wood chips from the growing mix with landscape fabric.

Water potted plants before transplanting them into your garden. When you remove the plant and its root ball from the container, spread out or cut all the roots that have grown in a circle inside the pot. These roots could eventually girdle or choke the plant if they are not redirected to grow out and away from the plant. This will help the new plant get established in the garden soil more quickly.

Monitor the plants carefully after planting and check if they need to be watered. Because the lightweight container soil in which most transplants are grown can dry out more quickly than the surrounding soil, they may need watering more often than nearby plants. Generally, new plants need more frequent but lighter watering than established plants.

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