Damson plums (Prunus domestica) produce a small tart fruit suitable for cooking and preserving. Varieties of Damson plums comprise Shropshire, Merryweather, Blue Violet and French Damson. With good care, a mature tree yields between three and five bushels of plums per tree, according to the University of Rhode Island. Damson varieties vary in winter hardiness, based on the rootstock, but varieties are offered for U.S. Department of Agriculture plant hardiness zones 4 through 9.
Damson plums develop best when trained to a modified central leader system. This system includes a major trunk with various well-spaced lateral branches. Prune your Damson plum during the dormant phase in late winter or early spring. Shape the tree and remove dead and diseased branches. Also split off any suckers that develop from the roots or trunk of the tree. Once the tree reaches your desired height, then cut the back just over the upper division. Preserve this stature by fortifying the very best and tallest branches every year.
The newly planted tree requires one cup of 10-10-10 fertilizer approximately six weeks after planting. After the first year, trees have been fertilized twice annually. In early March use 1 cup of 10-10-10 fertilizer for every year of tree age , up to a maximum of 12 cups. In August, employ 1 cup of calcium or ammonium nitrate per year of tree age , up to a maximum of 6 cups. Spread the fertilizer evenly under the tree canopy, avoiding the tree back.
While a few Damson plums have been self-pollinating, all kinds make better when the other European-type plum is planted nearby. Opt for a second tree that is a distinct European assortment of plum, but that flowers at the exact same moment.
You may have issues with birds and other creatures eating the plums before they are ready to harvest. Covering the tree using netting solves this issue and raises your own harvest. Damson plums are ready for harvest when the colour changes and the flesh softens. The plums will be deep blue, purple or black in colour and have a powdery look. Store ripe plums from the refrigerator.