Magnolias are large shrubs to medium-sized trees native to cold-winter regions across Asia and North America. They readily produce showy white, pink, violet or yellow flowers in spring and summer if they are provided with in adequate sunlight, are healthy, receive a winter chill period, and are of an appropriate size or age.
Ensure the magnolia, regardless of species, is receiving enough sunlight. A garden spot that receives at least 6 hours of direct sunlight is needed.
Examine the magnolia for signs of stress that affects its healthiness. Yellowing leaves and branches dieback can occur if soil is too dry, infertile, or alkaline. Root disturbance and soil compaction also stresses the plant. Extreme winter cold burns and kills leaf and flower buds even when dormant.
Expose the magnolia to a prolonged chilling period in its winter dormancy. This process, called vernalization, is required to initiate the formation of flower buds. If the winter is too warm, depending on the magnolia species, flowers may never develop.
Allow plants to mature and establish before assuming it does not flower. Seedlings likely will not flower until they reach a size where their leaf growth provides adequate energy to produce flowers.
Fertilize the plant, according to label directions, with a granular slow-release fertilizer that is rich in phosphorus (P) and potassium (K). An overabundance of nitrogen (N) causes more leafy growth.
Refrain from tip pruning your magnolia for at least one year. If you prune your magnolia in fall, winter or spring, you likely are trimming away next spring's buds.
Consult with your local land grant university's Cooperative Extension Service for recommendations on magnolia species and cultivars best suited for your region. The agency may also be able to inform you of recent trends in diseases or pests that may be affect magnolia flowering.
Do not plant magnolia shrubs or trees too deeply. This results in a slow but certain health decline, causing leaf drop, flower abortion and eventual death unless remedied with an intensive replanting.