Pomegranate trees (Punica granatum) require little trimming when mature, but formative pruning is essential for young trees. The process starts at planting time and continues the first three years while trees become fully productive. Heavy pruning reduces pomegranate yields. So knowing your purpose and sticking to it is important. Prune the trees according to their age, time the task right and use proper tools so pomegranates grow healthy and productive.
Train First-Year Trees
Prune very young pomegranate trees to establish their ultimate form and structural strength. The trees can be trained to a single-stem form or allowed to grow multiple stems, as they do naturally.
At planting time, select a strong, single stem or five to six stems, depending on your preference for a pomegranate's form. Remove all other stems, and cut the tree back to 24 to 30 inches in height. This task stimulates branching and side shoots that ultimately benefit tree health, productivity and ease of harvest.
Pomegranate trees sucker heavily, growing abundant new stems from their bases. Remove all suckers as they rise from the ground throughout the growing season.
Establish Structure in Year Two
Second-year pruning starts the first winter after planting. Prune pomegranate trees while they're still dormant, before their spring growth begins. Remove dead, damaged and crossing branches. Then choose three to five strong, well-developed shoots on each main stem to become primary branches. Keep a vase-shaped structure in mind for each tree.
Remove all other shoots, and prune the primary branches back by one-third their length. This technique encourages the development of spurs -- short branchlike growths that bear future flowers and fruits. It also opens the trees so fruit-enhancing light reaches their interiors.
Remove all suckers and sprouts along trunks at this time. Remove all new suckers and sprouts as they appear through the growing season.
Trim Established Trees for Productivity
Formative pruning pays off by year three, when pomegranate trees usually bear their first full crop of fruits. With form and structure well-established, mature trees need little maintenance pruning from that point forward.
Pomegranates flower and bear fruits on new branch tips and spurs from 2- to 3-year-old wood. Pruning on a regular basis reduces fruits. Newly exposed branches are sun-sensitive, too. So keep pruning to a minimum. Remove all damaged and crossing branches in late winter, and remove suckers and sprouts throughout the year.
Pomegranates survive winter extremes in U.S. Department of Agriculture plant hardiness zones 8 through 10 and may survive but sometimes die to the ground in USDA zone 7b. In any of those locations, though, their hardiness requires full dormancy. Avoid all fall pruning; it stimulates new growth, inhibits dormancy and leaves trees susceptible to cold damage.
Choose the Right Tools
Clean, crisp cuts heal faster and make pruning wounds less vulnerable than ragged cuts to insects and diseases. Use sharp, bypass-type pruners, which slice stems cleanly with scissorlike action. Hand pruners give sufficient leverage for cutting suckers, sprouts and stems with diameters less than 1/2 inch. When pruning midsize stems, use long-handled bypass loppers. Tackle stems 1 inch in diameter and larger with a sharp pruning saw.
Always sterilize pruning implements with household disinfectant before and after you prune. If insects or diseases are suspected, then disinfect pruning blades before and after each cut. Disinfection helps prevent the spread of diseases and pests to other parts of a pomegranate and to other plants.