Fruit Trees in Containers
For folks who want to grow their own fruit, but who don't have adequate space or a suitable climate, growing fruit in containers offers several opportunities. Cherries, peaches, figs, apples, tangerines, lemons, and limes are among the many types of fruit trees that thrive in containers. And, you can grow them in just about any region of the country. Of course, container-grown fruit trees produce fewer fruit than full-grown trees, but fresh limes and lemons on a cold winter day in Vermont, for example, are refreshing, not to mention soul-stirring.
Some container-grown apples and cherries (deciduous, or leaf-dropping, trees) will not fruit properly in some mild-winter areas because they require a long period of cold temperatures. Ask your nursery staff about varieties that require a shorter cold period (also called "low-chill" varieties) and that do well in mild-winter regions.
Where to Buy Container Fruit Trees
To get fruit through the winter, buy and plant fruit trees in the Spring. Most plant catalogs and nurseries contain a selection of fruit trees that can be grown in containers. Trees ordered from mail-order catalogs are shipped bare-root.You should plant your tree within a day or two of receiving it, but only after soaking the roots overnight in warm water.
Nursery-bought trees will be either in containers or balled and burlapped. Look for trees with branches arranged symmetrically around the trunk and without broken or diseased limbs. Avoid buying rootbound trees (roots circling the container), and prune any broken or damaged roots before planting.
Choosing a Container
Containers are available in almost every size, shape, and material. Containers made of untreated, rot-resistant wood are good options, but wood rots eventually. Clay pots dry out faster than wooden ones, and fungi and bacteria can grow in the porous surfaces. Also, old clay pots can build up enough fertilizer and salts to make them impermeable to air and water. Plastic pots, on the other hand, are light inweight, but they heat up in the sun. All containers must have adequate drainage holes.
A good fruit-tree container is a 15-gallon pot, which is large enough for a 5-foot tree. Such a container could weigh between about 70 and 125 pounds, depending on what the pot is made of, the size of the tree, and the type of soil. Weight is no small consideration if you have to move the container with the tree in it.
For a citrus tree, a conventional container, called a Versailles planter, is especially well suited because the sides can be removed to make it easy to add or remove soil without uprooting or having to lift the tree out of the pot. The tree it holds can be 10 feet tall, and the planter with tree can require four people or a forklift to move it. Citrus-tree soils are especially heavy because they require sand, which adds considerable weight. The wheeled platforms sometimes advertised for use in moving large plants usually list a rating of the ranges of planter weights between 150 and 400 pounds.
A good container mix ensures thorough soaking and good drainage to nourish and support the plant. When water runs right through or down the edges of the mix, leaving dry places, the plant should be repotted in the same-sized pot or in a larger one.
Here is a good container mix for growing fruit:
Purchased container mix is available in bags of 3 cubic feet ($15 wholesale, $30 retail). Read the ingredients, and add sand to make the mix heavier if necessary. Pro-Mix, Customblen, and Fafard brand mixes don't contain sand, but Metro-Mix 200 does.
Fertilizing and Watering
Fruit production requires regular fertilizing all year long. Monthly feeding is a good regim to maintain. Cut back the nitrogen in fall and winter to avoid encouraging new growth in those seasons. If your container mix includes a slow-release fertilizer such as Osmocote, it's good for several months. After that time, you have many choices, from the garden store's one-size-fits-all to the specific fertilizers suggested by the tree-supplier. Ask his or her advice, and follow the instructions that came with the fertilizer.
The most important part of watering is proper drainage. Between waterings, the soil should dry well, but it shouldn't dry out completely, because dryness can cause fruit to drop. An outdoor container-plant in the sun can dry out very quickly and needs more than one watering per day. Protection from the sun reduces soil temperature, and burying the container allows rooting into the ground through drainage holes for less dependence on daily waterings.
Excess wetness or poor drainage can lead to root-rot (Phytophthora) in susceptible plants. However, you should overwater moderately once a month to leach out fertilizer residues.
Hedge Clipping and Root Pruning
Pruning controls a tree's size and shape, maximizes fruit production, and maintains tree health. Hedge clipping and "cleaning out the inside" are the minimum treatments.
To prune, remove all foliage from the inside branches of the tree so that most of the foliage grows on the outside. Pay attention to the fruit location. On many citrus plants, the fruits are on the tips of small branches, and many of these fruits are always left, even after the most severe pruning.
During the first few years, you may prune a newly transplanted tree, but allow the tree to increase in size several inches a year. As it approaches mature size, prune to limit its increases to up to 1 inch per year. Most container plants eventually reach an optimum size for a specific container size. Fruit trees, especially citrus, can live more than 75 years, so annual repotting is the best way to maintain the health and vigor of both plant and soil.
In the spring, repot the plants before putting them outdoors for the summer. Remove about an inch of the rootball, and comb the root tangles. Prune a similar amount of foliage at the same time. Additional summer pruning is necessary to limit the tree's size.
The best pruning job I've ever seen was done by a herd of cows on a wild apple tree. Every spring, the cows grazed the tree down to a stub; they ate most of the new growth from summer until fall, when they would leave it alone. This tree was a perfect sphere of foliage about 5 feet tall and about 60 years old. The cows had created a perfect bonsai specimen.
As the art of bonsai demonstrates, you can limit almost any tree to any size by careful pruning. I have a 1-foot-tall 'Ponderosa' lemon in a 1-gallon pot that produces 3 pounds of fruit a year. Of course, the smaller the pot, the more attention you must pay to watering, fertilizing, root and foliage pruning, and repotting.
Deciduous trees, such as apples and cherries, require a period of temperatures between 32o to 40oF. in order to fruit properly the following year. Gardeners in mild-winter regions should look for fruit trees adapted to fewer chill hours.
If you're not in a mild-winter zone, move your fruit trees indoors in winter or protect them outdoors. After their leaves drop in the fall, deciduous trees should be kept moist and moved to an unheated garage. You can also keep them insulated outdoors to prevent freezing and thawing of the roots. To insulate your outdoor trees, tie up the branches, create a wire-mesh cylinder (around the tree and container) 1 foot wider than the tree canopy, fill the cylinder with leaves or straw, wrap the cylinder with burlap, and cover the top with plastic to shed water.
Citrus and tropical trees should be moved to a heated greenhouse or solarium before the first frost to overwinter indoors. Some citrus and tropicals m need supplemental light and heat in winter for best fruiting. However, excessively hot and dry conditions can cause citrus to drop fruit. In that case, you should mist the foliage with tepid water. Citrus will often have flowers and fruit at different stages on the same tree, and ripe fruit can be left on the tree for weeks.
Pests, Diseases, and Sanitation
Proper sanitation can prevent or control many problems; but the longer you put it off, the harder it gets. For your trees, a regular shower, a spray with an insecticidal soap such as Safer (an organic treatment), and a gentle scrub all over with a soft brush will control most pest outbreaks. For serious scale infestation, use a light horticultural oil spray once a year or get the appropriate beneficial insect predator, available for most insect pests.
Prevention is the best approach to diseases. Find varieties and rootstocks that are resistant to the microbial problems in your area. It deserves repeating: Sanitation is the most important aspect of container and greenhouse growing; as gardeners say, when in doubt, clean it up, and clean it out.
Growing trees in containers can produce an abundance of fruit (and satisfaction) for city-dwellers, people with limited space, or folks who live in unfavorable climates, so don't feel that your location limits your fruit-cultivation options.
William Ross grows many kinds of hardy and tender fruit trees in containers at his home in Danby, Vermont.
Photography by National Gardening Association