With their fragrant blossoms and sweet fruit, plum trees (Prunus domestica) are among gardeners' favorite trees to cultivate. Plum trees will grow and bear fruit in most of the country and do not require excessive care, but in order for them to bear fruit you must plant two or more different varieties that will cross-pollinate. It is best to space them 18 to 22 feet apart.
Sun and Temperature Needs
Plum trees need at least six to eight hours of direct sunlight per day to grow lush and bear fruit. Although they will grow in less sunlight, they will be leggy and produce little or no fruit without substantial sun. Plum trees can withstand cold temperatures, but the flowers and fruit of trees grown in cooler areas can be susceptible to frost. Protect plum trees from chilly wind and temperature fluctuations by planting them near any non-north-facing wall or on a slope that allows cold air to "drain" into lower areas. They will retain more heat this way.
Plum trees adapt to a variety of soil conditions, but they truly thrive in fertile, well-drained, sandy, loamy soils with a pH between 6 and 7. To determine the soil's pH, contact the county extension for a soil test kit, sample the soil as directed and follow any amendment recommendations provided with the results. If soil is especially poor, plum trees will benefit from working wet peat moss or compost into the planting hole. Use a ratio of one part peat moss to one part soil.
Adjust fertilizer rates based on the tree's yearly growth. Young stone fruit trees, including plum trees, typically have shoots that grow 15 to 20 inches per year. Once trees begin bearing fruit, shoots grow 8 to 12 inches per year. If the tree is growing less than this per year, apply 25 percent more fertilizer per application. If the tree is growing more than this do not apply nitrogen fertilizer as it is likely the tree does not need it.
New plum trees should not be immediately fertilized after planting. Instead, fertilize them before their leaves emerge in early spring, a minimum of six weeks after planting.
Things You'll Need
- 10-10-10 balanced dry, granular, slow-release fertilizer
- Calcium nitrate or ammonium nitrate
- Watering can or hose
Fertilizing in First Year
Spread one cup of 10-10-10 granular fertilizer evenly across an area 3 feet in diameter for newly planted trees.
Spread 1/2 cup of calcium nitrate or ammonium nitrate evenly over an area 2 feet in diameter in mid-May and again in mid-July.
Water the tree as usual after applying fertilizer to help nutrients reach the roots.
Fertilizing Beyond First Year
Fertilize plum trees two times per year, during the growing season, beginning in their second year.
Apply one cup of 10-10-10 fertilizer per year of tree age, up to 12 cups, around the tree. Spread the fertilizer evenly around the tree in an area equivalent to the diameter its limbs reach, known as the drip line.
Spread 1 cup of calcium nitrate or ammonium nitrate per year of tree age, up to 6 cups, on the ground around the tree. Apply the fertilizer evenly in an area equivalent to the diameter its limbs reach.
Water as usual to help the fertilizer seep into the roots.
Avoid overfertilizing as it can harm plum trees. Spread the fertilizer over a wide area and avoid applying fertilizer only near the trunk.
To keep a plum tree hydrated, water it at a rate of 3 to 5 gallons of water per week during the months it actively grows. If more than an inch of rainfall falls in a week, do not water it that week. Avoid overwatering plum trees as this can cause their roots to rot and fruit to split. Once a plum tree is established, water it two times per week until the water is absorbed into the soil but before runoff occurs. In very hot areas, plum trees can be watered up to three times per week.
To help the plum tree grow and produce fruit, pruning while it remains dormant in spring is necessary. At the beginning of each growing season, remove any dead, weak or broken branches as well as suckers (small branches growing from the base of the tree). Thin out the top of the plum tree to allow sunlight and air circulation by removing entire branches from the top of the tree. Avoid pruning after mid-August.
Disinfect hand shears or loppers by soaking them in 1 part bleach and 3 parts water for five minutes to help prevent the spread of disease.