The ability of a dormant plum tree to bloom relies heavily on its age, ambient cultural conditions and care for the year or more leading up to the traditional spring bloom period. Weather plays a key role, as does moisture, timing of pruning, and soil space and quality. Forcing a dormant tree to develop buds and bloom will require troubleshooting a number of factors to optimize the tree's health and well-being. Plum trees reach maturity and begin to flower and bear fruit consistently four to six years after being established in the soil.
Ensure that your plum tree is receiving a full sun exposure all day, every day. Sun will help to warm the soil and tree tissues, triggering a break from dormancy and encouraging bud formation and swelling. Prune away any overhanging branches from adjacent or nearby trees that may be blocking the sun from reaching your plum tree.
Water your plum tree regularly to keep the soil evenly moist at all times but not persistently soaking wet. Drought stress can limit bud development and bloom.
Mulch around the base of the tree with shredded bark or compost to keep all competitive weeds and plants at bay; pull any plants or weeds that develop under or near the tree. Organic mulch will also gently boost soil fertility without chemical fertilizers.
Fertilize your plum tree lightly and within the label-recommended dosage range for your fertilizer of choice. More fertilizer is not better, as too much nitrogen will work against you to impede the development of flower buds.