There are numerous reasons for plants not blooming. Three major factors – weather, stress and immaturity – are largely outside a gardener’s control. An observant and informed gardener, however, can manage some of the surrounding circumstances.
Unseen stress is tough to identify as a reason for non-blooming. Bulbs may have been overheated in transit or storage, plant roots may have dried out at some point or growers may have forced plants into early bloom. With time to recover, some will bloom again, some won’t.
Buds won’t open when they are infested with insects. If you find holes chewed in flower buds, open one up and look at what’s inside. If it is full of bugs, there probably isn’t much flower left. Remove and destroy insect laden buds. A severe infestation of sucking insects like lacewings, thrips and white flies can stress a plant so that it ceases flowering. Monitor and control damaging insects to prevent problems.
Inadequate chilling time is the reason we simply don’t grow some fruit trees, tulips (as perennials) and plants like lilacs and peonies in the South. They won’t bloom without their required chilling hours.
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A warm winter may convince a tree or shrub to come out of dormancy early. A cold snap after buds have formed can kill the them, resulting in weak or no blooms.
Sun-loving plants become stressed when they don’t get enough sun. Common responses to stress are failure to form buds and bud drop. Full sun plants need at least 6 hours of sun per day to set their buds. They thrive with afternoon sun. Morning light is relatively cool and alone it may not be enough for the plant to bloom. A western exposure produces a more floriferous plant than an eastern exposure. Sun loving plants like tomatoes and most roses need day long sun.
Monitor your and your neighbor’s changing landscapes. You may find full sun areas becoming dappled or partly sunny from increasing shade cast by maturing trees and shrubs. Conversely, the removal of a tree or shrubs may suddenly allow full sun into a spot that was previously in shade. Some plants will need to be moved to more favorable conditions.
Overcrowding can creep up on a gardener, especially with bulbs as they multiply underground and out of sight. Pay attention to your amaryllis, daffodils, daylilies and iris. When they are overcrowded they will cease blooming. Keep a note in your garden journal of when they were planted to help you remember when to divide them.
Proper fertilization influences flowering. Too much nitrogen produces green leafy growth instead of flowers. Plants need phosphorus or potassium to support blooms. However, be aware that a dose of fertilizer is unlikely to solve a nonflowering issue.
Expect annuals to flower the first year, biennials the second year. Perennials also typically bloom the first year.
Trees and many shrubs don’t bloom until their roots are adequately developed. They need a specific period of time for their roots to mature. Often newer varieties have been bred to flower earlier than older types that take longer to establish.
Consider your plant’s age and variety before you look for blooms. Many fruit trees require five–six years to establish and bloom. Some fruit trees flower only every other year. Apple trees can take eight-10 years. Gingkoes need 15 years. You will have to wait for magnolias and wisteria, too. If the plant tag doesn’t give you flowering information, ask your nurseryman what you should expect.
Gardeners can take responsibility for a plant’s nonflowering when they have chosen a plant unsuitable for our climate, not guarded against transplant shock, planted too deeply, provided inadequate growing conditions, watered too much or too little or pruned incorrectly. Consider all these issues when you try to determine why a plant doesn’t bloom.
For the best performance and floriferous plants grow the right plant in the right place and use native and adapted plants that are suited to our area.
One more thing: Watch for changing bloom times as our climate continues to warm.
Reach Debbie Menchek, a Clemson Master Gardener, at email@example.com.