Oregon State University Extension Service 
SALEM, Ore. – You don’t need a backyard or other piece of property to grow a tree if you have a porch, patio or balcony – and a large gardening container.
You are likely, however, to need information on how to choose and grow your container tree, according to Neil Bell, Oregon State University Extension horticulturist in Marion County.
“Pay attention to the expected size of a mature tree,” Bell said. “For obvious reasons, a tree whose mature size is small will be most adaptable to container growing. The size of a tree is usually proportional to the size of its root system, and containers will restrict root growth.”
Pots should be about as wide as they are high for best insulation of the roots. Clay pots are heavier than plastic but are more stable in windy conditions, especially with larger trees.
Smaller species and dwarf varieties of standard species are good candidates for containers. Evergreens such as Mugo pine (Pinus mugo), Korean fir (Abies koreana), cryptomeria (Cryptomeria japonica), Skyrocket juniper (Juniperis scopulorum ‘Skyrocket’), boxwood (Buxus spp.), English yew (Taxus baccata), strawberry madrone (Arbutus unedo), dwarf camellias, and just about any dwarf conifer can grow in containers.
Deciduous trees that do well in containers are Japanese maple (Acer palmatum), star magnolia (Magnolia stellata), cutleaf vine maple (Acer circinatum ‘Monroe’), dwarf weeping birch (Betula pendula ‘Trost’s Dwarf’), lacebark elm (Ulmus parvifolia ‘Frosty’, ‘Seiju’ or ‘Yatsabusa’ and crepe myrtle (Lagerstroemia indica).
If you have sunny indoor space, citrus trees such as Meyer lemon, Baerr’s lime and mandarin orange, or other tender evergreens can be grown in containers outside in the summer and brought inside during the colder months.
Careful soil selection is critical to the health of the tree.
“Do not use soil directly from your garden,” Bell advised. “Instead, use a soil-based compost, with good organic matter content and preferably some perlite or pumice to make the mix porous, which keeps air in the soil.” Find these in bags at nurseries and in garden sections of other stores.
Caring for a containerized tree is more work than growing a tree in the ground. The roots can search for water and nutrients only within the confines of the pot, so you need to provide adequate amounts of both. Water regularly and fertilize with a balanced, slow-release fertilizer.
Protect the tree roots from winter cold by keeping the container in a protected spot or cool greenhouse or wrap the pot with insulating material during the coldest months.
“If a tree starts to outgrow its container, you have choices,” Bell said. “Plant it in the ground, plant it in a larger container, or prune the roots back by one-third and plant it back in its current container. Root pruning is a similar technique to bonsai and will help to keep the tree small.”
Trees in containers can be very pleasing on your patio or deck. With a little extra effort, you can enjoy your tree for many years.
By: Judy Scott
Source: Neil Bell