Growing plums in your Louisiana landscape

Story and Photography by A.J. Heinsz-Bailey

In the early 19th century, “plum” meant any desirable treasure, a coveted prize, or the best of a group. Now the word is used as an adjective describing something covetable, like a “plum role” in a movie. Living up to this reputation is not difficult for this succulent summer fruit. These gems have red, yellow, green, purple, or black skins with red, yellow, or purple flesh. 

They are not difficult to grow, but they do require regular inspections for insects and diseases. Covered in spring with snow white blossoms, followed in summer with juicy orbs rich in vitamins and minerals, plum trees are great additions to home landscapes. 

There are a few important details to consider before buying a plum tree. Plum trees require chilling hours so get the right type and variety for your part of the state.) In general, coastal areas get 200-300 hours; South Louisiana gets around 400 hours; central parts of the state get around 500-600 hours, and North Louisiana gets 700-800 hours. 

There are three major types of plums for the home garden. The Japanese or Chinese plum (Prunus salicina) is grown in Louisiana. The trees are usually grafted onto peach rootstock in our area. The peach rootstock is used because it has more desirable traits such as increasing tree life expectancy. The European plum (P. domestica) prune plum likes cooler climates and is not grown in Louisiana. The indigenous American species in Louisiana are the Chickasaw plum (P. angustifolia) and American plum (P. americana). 

You will need to plant two or more trees for cross-pollination so have enough space. Trees should be planted 15-20 feet apart. Even the self-fertile varieties benefit and produce more fruit when they are cross pollinated. ‘Methley’ and ‘Santa Rosa’ are the most popular pollinators for other varieties in Louisiana. 

Prepare planting sites a couple of months before actual planting. The reason for this is so the soil can be tested and the pH adjusted to 6.0-6.5. Proper planting includes placing them in full sun – eight to 10 hours – in well-drained, fertile soil. The site can be built up if necessary to provide good drainage. Do not fertilize at the time of planting; wait at least six weeks. Mid-winter is the optimal time to plant bare-root dormant trees because it allows for root development before spring growth. Also planting in early spring gives the tree a chance to establish itself before stressful hot temperatures of summer. Container-grown trees can be planted later in the season after breaking dormancy but before the heat of summer.

Dig the planting hole a little wider than the root ball and at least 18 inches deep. Select smaller trees as they adapt better than larger ones. The trees should have healthy white roots with no brown streaks. Plant the tree about 1-1/2 inches above the soil line. It will settle to the soil line after watering a few times. Planting too deep will cause poor performance. After planting, cut the tree off about 24-30 inches above the ground, which forces new branches to grow into a modified open-centered tree. Keep the area around the newly planted tree free of weeds. 

Plums start bearing fruit when they are 4-5 years old. The life expectancy is 15-20 years. Plum varieties for the South have been developed by Auburn University in Alabama, Texas A&M, and the University of Florida. 

Water deeply at least once a week if there has been no rainfall. Enough water is critical when newly planted trees are trying to grow roots and branches. However, overwatering clay soils can lead to death from drowning. The roots die and rot if the soil is too wet. Water applied as the fruit ripens will help increase fruit size. Watering twice a week with 2 gallons of water is enough for a small tree in most cases. The larger the tree the more water it needs. Less water is needed in the dormant season. 

Weeding and mulching is easy. Weeds should be removed from around the base of your plum trees by hand. Apply pine straw or suitable mulch that does not mat around the base of the tree. Do not pile the mulch directly on the trunk of the tree. 

Start your fertilizing program in the beginning of the second year after planting. Chemical or organic fertilizers can be used. Trees need iron, zinc, manganese, copper, boron and magnesium. Application rates change with the age of the tree. The first application will be in March. Apply 1 cup of 13-13-13 for each year of tree age to a maximum of 12 cups for mature trees. In August, apply 1 cup of calcium nitrate per tree per year of tree age up to 6 cups for mature trees. Be sure to broadcast the fertilizer out to the drip line and don’t put the fertilizer near the trunk. Water or lightly rake the fertilizer when finished with the application.

After the first growing season while the tree is dormant you will begin pruning and training. This pruning will establish the framework of the trees. At planting time when you cutback the top of the tree it forced out strong vigorous shoots which are easy to train. You are trying to develop an open form that allows for air circulation and sunlight penetration. The modified open center system of pruning will increase fruit production and promote overall tree health. Check for borer presence or damage while you are working with your trees. Once mature only a little pruning is required to thin excessive and interfering branches. Your goal is to maintain the tree at an easy picking height. Thin the fruit four to six weeks after blooming. Fruit should be 3-6 inches apart. 

The three most common insect pests are plum curculios, stinkbugs, and peach tree borers. Timing is a key to controlling insects effectively. The female curculio is a weevil that deposits an egg on the immature plum. The developing worm destroys the fruit. Malathion is effective in the control of this pest. Be sure to read the label before applying. Peach tree borers attack the plum below the graft. Recognized by the fras and gumosis on the trunk the developing grub can be killed by hand. Remove the gumosis to reveal the grub.

Diseases of plums are similar to those of peaches. Fungicides labeled for peaches can be used on plums. Bacterial canker and black knot, a fungal disease, can reduce fruit production and tree longevity. Black knot is a lumpy shaped growth found on the limbs. Prune it off and get rid of all the infected branches. Brown rot is another fungal disease that attacks branches and fruit. It causes twig dieback and rotting of the fruit.

Cross-pollination is possible if the bloom times of different varieties overlap. Plant three trees if you have the room in case one doesn’t survive. Fruits will be produced on spurs and the previous season’s growth. Early flowering, which results in crop loss from unexpected freezes in late winter and/or early spring, is an avoidable hazard. Some years there will not be a crop. The taste of a fresh picked ripe plum is worth the risk. 

Summer is harvest time. Plant different varieties to extend your harvest .A mature plum tree will produce 30-50 pounds of fruit in a season. 

If you would like a small tree that explodes with white flowers in the spring, lush foliage and interesting bark, and finishes its season with succulent fruits consider a Japanese plum. You will not be disappointed. It is easy to become “plum” crazy for plums.

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