Containerized plants are popular and convenient ― and in fact, many kinds of shrubs and trees are sold only in containers. Such plants offer certain advantages. They are sold throughout the growing season; they are relatively easy to transport; and, unlike bare-root and balled-and-burlapped plants, they don't have to be planted immediately. Furthermore, these plants can be purchased with flowers, fruit, or autumn leaf color on display, letting you see exactly what you're getting.
When selecting container-grown plants, look for healthy foliage and strong shoots. Check the leaves and stems to be sure no insects are present.
Inspecting the root system is more difficult, but healthy roots are vital to successful establishment of container plants. A relatively small plant in a 5-gallon container may not be well rooted, usually because it has recently been moved to the larger container from a 1-gallon pot. (If you buy such a plant, it's wise to keep it growing in the container until it develops a good root system.)
On the other hand, if a containerized plant has been in its pot for too long, it may be rootbound, with tangled and matted roots that coil around the inside of the pot. If you see roots protruding above soil level or husky roots growing through the container's drainage holes, the plant is rootbound.
A plant that looks large for the size of its pot is often rootbound as well. It's best to avoid rootbound plants ― but if you do buy one, be sure to loosen the roots before planting.
Plants in containers are available in several sizes. One- and 5-gallon pots are the most common; which of these you buy will depend on how much immediate impact you want the plant to have and on how long you're willing to wait for it to grow. Keep in mind, though, that smaller plants grow quickly; within 3 years of planting, a 1-gallon plant will usually have reached the same size as a 5-gallon one set out at the same time.
Removing plants from containers
• Plastic containers and metal cans. Tap sharply on the bottom and sides to loosen the root ball. The plant should slide out easily. If it doesn't, cut plastic containers down both sides with bypass pruners. To cut metal cans, use tin snips (watch out for sharp edges).
• Pulp pots. Tear the pot away from the root ball, taking care not to damage the roots.
1. Dig a hole as shown in the article Planting bare-root shrubs and trees. Spread roots out over the central plateau of firm soil. The top of the root ball should be 1 to 2 inches above surrounding soil.
2. Backfill with the unamended soil you dug from the hole, adding the soil in stages and firming it around the roots with your hands as you work.
3. Make a berm of soil to form a watering basin. Irrigate gently, keeping the stem or trunk and crown of the plant dry to prevent fungal infections. Spread a layer of mulch around the plant, keeping it several inches away from the stem or trunk.