Find the trunk flare when planting new trees

It’s that time of year when new trees and plants are finding their place in our gardens.

One of my pet peeves in gardening is seeing a tree that is planted too deep, and unfortunately, I see a lot of them. The top of the root ball isn’t an accurate guide for determining the planting depth for your new tree. Instead, locate the trunk flare — the place where the trunk widens at ground level. If the trunk flare is not showing, open the burlap to find the flare. You will need to plant the tree higher in the hole and very carefully remove the excess soil above the roots to expose the flare. Generally, planting 2 to 3 inches higher than ground level is a good idea in heavy clay soils. It’s best not to amend the backfill going back into the planting hole, but OK to amend the soil at the surface around the tree.

Plants that have been grown in containers should be moist when planted in your garden. When you remove the plant and its root ball from the container, spread out or cut all the roots that have encircled the root ball. These roots have grown in a circle inside the container and could eventually girdle or choke the plant if you don’t redirect them to grow out and away from the plant. This will help the new plant get established in the ground more quickly. Also, monitor these plants carefully for watering after planting; the lightweight container soil can dry out quickly and stress the plants. Generally, plants that you’ve transferred from containers need more frequent — but light — watering for the first few weeks to help them get roots established in the garden soil.

I like planting annuals in containers at home to add color and interest to my garden. The containers you’ll want to use for seasonal plantings should have at least one bottom hole for drainage. A layer of gravel at the bottom of the container isn’t necessary. Fill the container with a lightweight, fast-draining soilless mix — avoid heavy garden soil. Leave enough space between the top of the growing medium and the pot to make watering easy. You can partially fill very large containers with empty plastic pots to conserve your soilless mix.

Some good news: It is now OK to start planting your warm season vegetable plants, like tomatoes and peppers. Cold weather that is typical in early May can stunt the growth of these plants, but we’re past that by now.

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