Tips for Growing Trees in Pots
A great option for smaller outdoor spaces or rental properties, container trees can actually expand the varieties you are able to grow. Here are some tips for which trees to choose and how to keep them healthy.
Why Container Trees?
Growing trees in containers is a good idea for a few reasons. To start, delicate varieties can easily be protected. For example, trees that normally wouldn’t survive in cold climates are able to be moved indoors during the winter months. Similarly, pots allow you to grow tree species that are not suited to your particular outdoor soil type.
In addition, containers enable people with small outdoor areas, like a patio or porch, to be able to incorporate a tree into their space. Potted trees are also great for renters, as they can take it with them when they decide to move.
Suitable Trees for a Container
For the most part, slow-growing trees are the best choice, in addition to dwarf varieties or trees purposely grafted to limit their full-grown size. For example, the dwarf Alberta spruce makes an ideal container tree. If watering plants is not your strong suit, consider finding a tree that has a high drought tolerance as well.
Popular Varieties for Potting
Due to its striking beauty, the Japanese maple tree makes a strong choice. It comes in a single-stemmed variety as well as multi-stemmed. They both make gorgeous focal points. The ‘Orange Dream’ Japanese maple variety is particularly exciting, as it provides constant color changes during the growing season.
Other favorites include the flowering cherry — a stunning, flowering tree that is small in stature and full of vivid color in the autumn — and serviceberry, which also features beautiful flowers in the spring and breathtaking color in the fall.
Olive trees and the Rocky Mountain juniper and also make great container garden additions. Star magnolias are appropriately named, as they do well as a feature plant. Topiary-friendly English holly, a gorgeous slow-growing tree, creates a welcoming entrance when flanked on either side of a doorway or staircase.
Potted Fruit Trees
Although soft fruit trees require protection in the winter, dwarf varieties of pear, apple, plum, apricot and peach all make good potted plants. Just keep in mind that they’ll need attention, including good-quality, free-draining compost; frequent watering during hot temperatures; a sheltered, full-sun location; and fertilizing. Simply fill your container with compost combined with one-third grit sand, then place the potted tree in a full-sun area, feeding it with a high-potassium feed bi-weekly during the growing season.
To help prevent any possible damage from overladen trees, consider removing some of the fruit-bearing shoots and positioning the container in a safe place — out of high winds or secured to a wall — so that the tree cannot blow over.
Pollination is another important factor to think about. Generally, in order to bear fruit, fruit trees require another tree of the same type flowering simultaneously with which to cross-pollinate. However, self-pollinating varieties do exist. For trees kept in a greenhouse, hand pollination may be necessary.
Best Soil Type
A loam-based compost is appropriate for most trees, although some (maples) prefer soils that are acidic.
Mix the compost with one-third grit sand before filling the container. Be sure to place gravel in the bottom of the pot first to enhance drainage and prevent the soil from running out of the pot’s holes. To water the trees, wait until the surface of the soil is completely dry and then drench it. Adding a layer of mulch on top of the soil helps retain the water. Also, footed pots work well on patios, allowing water to drain freely.
Feeding Container Trees
Potted trees are going to require more attention than those planted in the ground. For example, repotting every other spring is highly recommended, along with swapping out about one-third of the soil with new compost for a nutrient injection. Tip: Mix the new compost with a slow-release fertilizer for an additional boost.
To Prune or Not to Prune
Aside from topiary, slow-growing and dwarf tree varieties generally need very little pruning. Simply treat potted trees the same as you would their larger counterparts.
As for fruit trees, thinning out fruits during the growing season may be necessary so that branches aren’t damaged under the weight. Light trimming can also help keep disease at bay, including brown spot, canker and peach leaf curl.
Best Type of Container
Containers should be scaled to the size of the tree — in other words, avoid using a giant pot for a tiny tree. Instead, repot the tree into a slightly larger container as needed every few years.
Other things to think about when it comes to containers are durability, water retention and style. Materials like terra cotta and concrete are sturdy and heavy so that they won’t blow over. But frost-resistance is important as well or else your container will crack in cold weather. In addition, terra cotta has a tendency to dry out faster than other materials, so trees will need watering more frequently.
Wood planters do better in the cold and retain water well, but they have a tendency to rot if not lined. Metal containers are durable and stylish, but can rust through. Cor-Ten steel pots are a good option for metal planters, as the rust provides an aesthetically pleasing, self-protecting layer. Plastic containers are both durable and frost-resistant, in addition to being lightweight, versatile, and easy to manipulate. Also, many different colors and styles are available, including those made from recycled plastic.