When you think “container garden,” it’s often flowerpots and window boxes that first come to mind. But potted trees like Japanese maples, junipers, locust and citrus can really pack a punch of beauty and anchor a container garden by providing maturity, scale and permanence.
A potted tree can anchor and focus your garden, providing the elegance and prominence of statuary to an open setting.
Photo Credit: ©2000 Dolezal Publishing/Reed Estabrook
The breadth and depth of a tree’s root ball will help you determine the correct container size. Place the container in its ultimate location before planting, unless you have the means to move it safely after planting.
Photo Credit: ©2000 Dolezal Publishing/Image Point
Evergreen topiaries result from careful pruning to direct growth in spring before new “candles” form on the branches.
Photo Credit: ©2002 Dolezal Publishing/Donna Krischan
Don’t let the idea of planting something as large as a tree intimidate you. Planting trees in containers is similar to planting anything else in a pot – though the pot is larger. And while you can plant trees any time of year, fall and spring are best because they give trees a better start to the growing season.
All kinds of trees work in planters, but the best candidates are dwarf and slow-growing varieties. Conifers – especially evergreens – require less food and nutrients than broad-leaved species, and they tolerate root restriction better than most tree species. Pines and junipers are naturally adapted to dry soil – a condition that’s common in many containers. If you’re not sure what kind of tree to add to you container garden, ask a knowledgeable staff member at your local garden center or contact your local Cooperative Extension Service for recommendations on what thrives in planters in your area.
Before you buy a tree, make sure that it isn’t root-bound. Most garden centers will assist you in partially removing a tree from its nursery pot. Avoid trees with circling roots. When you get the tree home, you can loosen the roots a bit more before planting by cutting 1-2 inches into the root ball vertically, using a sharp trowel. This will help the tree send fresh root growth into the surrounding soil rather than wind around itself.
Once you’ve got the tree, pick a pot that’s sized right for it. (Or if you’ve already picked a pot, select a tree that’s the right size for the container.) The planter should be twice the width and depth of the plant’s existing root system. Another rule of thumb is to allow a foot in container diameter for every 4 feet of tree height.
Generally speaking, trees in containers perform well in loose, well-drained native soil with a little added compost. Some species, such as Japanese maple, need a little acidic additive, and all trees benefit from adding a slow-release organic fertilizer to the planting soil to kick-start the transplant. When planting, add enough soil beneath the root ball to raise the tree’s height in the pot to the same level as it had been in its nursery pot. Keep the soil loose, tamping gently around the roots. Add a support stake or two, if necessary.
As with many potted plants, watering is the primary concern for trees in containers. When dry, a tree stops growing; the restrictions of even a large vessel, when combined with a lack of nutrients and restricted water, will dwarf or stunt any tree. When your tree begins to need daily watering, it’s a sign that it needs a larger pot – about an additional 4 inches in diameter.
Regular maintenance for containerized trees is fairly simple. Pruning amounts to snipping rogue stems, shearing suckers from below the graft on grafted trees and refining the tree’s shape. Prune after the tree is finished blooming or in fall in most climates. As far as fertilizer goes, it’s a good idea to remove the top 1-2 inches of soil and replace it with fresh mix each spring, as well as to add a dose of fertilizer at the same time.
While small container plants are popular candidates for dressing up a patio, deck or entryway, don’t overlook the beautiful impact larger plants can offer. With the right species and planter, your container garden can yield tree-mendous results!
