26 August 2009
In The Garden With the Fluvanna Master Gardeners
By Irene C. Burke - Fluvanna Master Gardener
Fluvanna County Extension Office: 434.591.1950
With crape myrtle (the Souths August lilacs) punching out the color these days, some are asking, "Why isnt my crape myrtle blooming and my neighbors is?" Wherever gardeners gather, the failure-to-bloom question crops up. Its about fruit trees, indoor exotics, shrubs, annuals, perennials - most any blooming thing.
Six essential conditions work together to create blossoms: plant age, temperature, light, nutrition, pruning practices and alternate year flowering. Environmental stressors - pests, disease, drought, transplant shock, pH imbalance, root crowding in the garden (but not in a pot), seed setting and planting depth, often account for missing blooms in sensitive plants.
During their juvenile phase, many trees and shrubs produce no flowers. The century plant (Agave Americana), crabapple, flowering cherry, tulip tree and wisteria are a few. Some lilacs may delay blooming for more than five years, if transplanted in early youth. Patient observation will help you recognize the immaturity problem, when all the other five conditions remain the same.
Some like it hot. Some like it cold. Late winter injury will kill buds, especially when preceded by a mid-season warming spell. Fruit tree and ornamental bloomers (dogwood and forsythia), and spring bulbs emerging too early are particularly susceptible. However, many plants require temperatures at least as low as 45 degrees (crocus, daffodil, Christmas cactus, tulip, peony, plus biennials - hollyhock for example) before blooming, but with a gradual, pervasive chill, not a sudden cold-snap.
For some plants the ratio of light to dark determines bloom. Long-day plants, Abelia grandiflora, Hibiscus syriacus, and Wiegela florida need 15 hours or more of light to bloom, while short-day plants, chrysanthemum, gardenia, and poinsettia prosper with 15 to 18 hours of low light and darkness. For others, a shady location of less than 8 hours of direct sunlight will increase foliage, while reducing or eliminating bloom.
Lush vegetation may result from heavy feeding with either compost or non-organic fertilizers, which will certainly shut down blooming. Often plants closest to a well-nourished lawn find themselves in this predicament. Heavy rains or deep watering will wash excess nitrogen from the soil with flowers returning in a year or two; the same remedy restores blossoms to houseplants.
Ill-timed pruning quickly removes flower buds, whether on new or old wood. Prune immediately after flowering, if you must. Clematis pruning is governed by the same principle for 2 bloom-time groups, so make a note of who belongs to which (spring and repeat flowering) and prune accordingly or youll easily err with a clip of next years buds. Prune the third group (summer and fall bloomers) when dormant, or just breaking dormancy. More drastic pruning of your clematis after three to four years of a tangled mess will restore them all to abundant blossoms. Check this web site for a complete list of clematis pruning groups: http://www.finegardening.com/pages/g00156_pe.asp
Alternate year flowering
This is an on-off phenomenon that is characteristic of the plant, not of your gardening routines - profuse blooms one year and scarcely any, the next. Kousa dogwood, some apple trees, and crabapples lead the crowd. Choose a different cultivar if this trait does not suit you.
After you have checked for the six essentials and still no flowers, look into environmental stressors. Systematically confirm and correct each, where it makes sense, then sit back and observe. Remember what the great philosopher, Yogi Berra once said; "You can observe a lot just by watching."
Tip of the Week
Banish the weeds from your lawn with a mulching mower, blade height set at four inches. Scalping the turf exposes bare soil, ripe for weed seed, perfect for soil erosion and just right for scorched grass. Pests and disease find the buzz-cut ideal for a silent invasion. Dont give them a chance.