New shade trees should be given the best start

Many trees are planted too deeply. To determine the proper planting depth for your new tree, 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 is best not to amend the backfill going back in the planting hole, but it is OK and can be beneficial 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 not redirected to grow out and away from the plant. This will help the new plant get established in the ground more quickly.

Monitor watering needs carefully after planting, as the lightweight container soil can dry out quickly and stress the plants. Generally, containerized plants need more frequent but light watering to get them established with roots out into the garden soil.

• My definition of a weed is a plant that is out of place. A good time to weed is when the soil is moist - the roots come out more easily. It's very important to get weeds out before they go to seed.

Watch for garlic mustard, which flowers (white) in its second year. If this weed is in full flower, then it is best to burn or put it into the trash to avoid spreading seeds in the garden. A small hand weeder or trowel is helpful.

Look for tree seedlings - such as buckthorn, mulberry and box elder - that tend to establish themselves in hedges and in the base of shrubs. Look closely and they are easy to spot. In areas where it is not practical to dig out the roots of these weed trees, then treat the stump with glyphosate promptly after cutting to kill the root system.

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