Is it okay to keep planting trees, shrubs and perennials in the summer as the weather gets hotter? — Gloria Jackson, Barrington
You should be just fine in continuing to install plants in your garden during the summer season as long as you are attentive to their care. The staff of the Chicago Botanic Garden in Glencoe installs new plants throughout the summer.
Any balled-and-burlapped trees and shrubs that you are purchasing now would likely have been dug early in spring and held since then. If they have been cared for properly in the sales yard, they will be in good condition to plant this summer. It is very important that the plant's roots have not been allowed to dry out before planting.
Try to choose plants that are fully leafed out with appropriate foliage color for the time of year. Leaves that are undersized and yellowing now usually are a sign of stress. Some types of plants, though, will have smaller leaves and be thinner than normal as a typical response to being transplanted. Ask your salesperson if the plant seems excessively thin or off color in its foliage.
There should have been some new growth on the tree or shrub while it has been held in the sales lot. But do not expect much, if any, new growth this year after planting, while the plant recovers and puts its energy into growing new roots.
Perennials and other plants that are grown in containers are also good to plant during summer. They should have healthy, full foliage with normal color for the season. When buying plants, look for healthy green buds; if they are present, your chances of a successful installation are improved.
Excessive browning on leaf edges and yellowing leaves are signs of stress; they may indicate that the plant dried out at some point. Some of the leaves will fall off of the plant if it was allowed to dry out repeatedly or for an extended period of time. It is not good when the plant's stems have died back in addition to dropping its leaves. You may see these stressed plants in the sale section at your garden center.
Plants that have been grown in containers for an extended period of time can become potbound, with densely matted roots, and will dry out very quickly in the heat of summer. Be sure to water them and break up the circling roots before planting them.
Pay close attention to watering after you plant in the heat of summer. In general, plants grown in containers will need more frequent light watering (two to three times a week, depending on the plant and weather) to get them established in the first few weeks after they go in the ground. The growing medium used in their nursery pots tends to dry out more quickly than the surrounding garden soil. As the plants root out into the garden soil, the watering can become less frequent and but deeper.
Plants that were balled and burlapped generally will need to be watered deeply once a week or so, depending on the weather and your garden's soil conditions. Be sure to water the roots at soil level, as evergreen foliage can shed water away from the root ball.
So go ahead and plant throughout the summer season. Just make sure you pay close attention to the care of the plants before and after installation.
Tim Johnson is director of horticulture for the Chicago Botanic Garden in Glencoe (chicagobotanic.org). Send questions to: Gardening Q&A, Sunday, Chicago Tribune, 435 N. Michigan Ave., Chicago, IL 60611-4041; e-mail to firstname.lastname@example.org.