He who plants a tree, plants a hope, writes poet Lucy Larcom. If you are ready to plant a hopeful sapling but lack a big backyard to forest, remember that many tree species grow happily in pots. Potted trees turn a roof deck or small patio into a garden bower, or use container trees to line a backyard footpath or property line. Fruit trees, like dwarf citrus, do well in containers, but that's not all, folks. Your choices are vast as long as you take climate and tree characteristics into account.
Consult Mother Nature First
Ask your sister, your mother-in-law and your friend with a green thumb what trees do well in your area, but the voice of authority is that of Mother Nature. Some trees naturally do well in the climate in your region, while others end up wilting or worse. The measure to look at is plant hardiness, meaning the ability of a tree to survive in a particular geographic area. The U.S. Department of Agriculture ranks regions and plants by hardiness zones, so match a prospective tree's hardiness to your region. If your area's winters are cold, pick plants at the top, rather than the bottom of the hardiness range, since the roots won't have so much ground soil protection.
Match-make a Happy Tree/Pot Union
Not every pot works well for every tree, so take time to arrange for a compatible match. First determine the appropriate size of the container. Virginia State University experts suggest that a pot hold 2 cubic feet of soil for every square foot of mature tree canopy. Bigger is also better when it comes to protecting roots from cold or hot temperatures. You'll also want match your pot type to your landscape, but appearance is not the only criteria. For example, terra-cotta pots are attractive, but plastic pots hold in moisture better. And be sure your pot comes with efficient drainage holes.
Blend Up Better Soil
One reason for planting trees in pots is the chance to improve on your own backyard soil, so don't miss the opportunity. Mix up a soil for your potted tree that drains well but doesn't get too compact with irrigation. Taking your tree type into account, blend both organic and inorganic components to create appropriate soil, including organic compost, pine bark and sand. If you are growing fruit trees, a mixture of equal parts sand, peat and bark or perlite works well.
Ready, Set, Plant
Once you have selected a tree, a pot and mixed up potting soil, it's time to move your tree to its new home. Because you are essentially repotting the tree, it is possible to act at any point when the weather is neither very hot nor very cold. But you may cause the tree less stress if you repot it during dormancy. Fall is a good time for potting a deciduous tree, and fall or spring works well for evergreens. Pot your tree near the place you intend the pot to stand.
Cover the drainage holes in the bottom of the pot with screen mesh. Pour 2 inches of gravel on top of the mesh to facilitate drainage.
Put on gardening gloves. Use your hands or a small shovel to add potting soil to the container until it is half full. Do not add fertilizer to the soil at this point. The addition of compost provides sufficient nutrients for many trees, and according to experts at the California Rare Fruit Growers Association, you should never add fertilize to a potted tree at least until new growth begins.
Remove the tree from its container and examine the roots. If the tree is root-bound, loosen the roots and prune back some of the larger ones. Always sterilize your pruning tools to keep from spreading disease to a healthy plant. Wipe the blades off with alcohol and allow to dry before starting the pruning task.
Place the tree into the half-filled pot at its prior planting depth. Hold it in place with one hand while you fill the pot. Add soil up to 1 to 4 inches from the rim. Press the soil gently around the tree's roots. Add a 2-inch layer of organic mulch to the soil surface, keeping it well away from the tree trunk. Irrigate generously. This helps regulate soil temperature and holds in water.
Place your tree in a sunny location unless it is a species that grows best in shade. Fruit trees require sun to produce, and many other trees grow better in sun as well.