Bloomless: What to Do When Your Plant Is a Dud

One of the most common frustrations in gardening is non-blooming plants and shrubs, says Dr. Ken Tilt, an Alabama Cooperative Extension System horticulturist.

"One of the most frequent questions I hear is, Where are my flowers? or Why didn’t my plant or shrub bloom?" he says. "There are a number of reasons that plants turn out to be duds."

Tilt says it takes some detective work to get to the bottom of the problem.

"But the answer can be found if you ask enough questions," he says. "Ask yourself things like has the plant ever bloomed before? Is there enough light? What has the weather been like? Have you had any freezes? Was there a drought last year? Was there too much water? Has anyone gotten some new pruning shears and tested them out on your azaleas or other plants?"

If you fertilize a very healthy plant four times a year and it still does not bloom, examine the type and quantity of fertilizer you are using, he says.

If the fertilizer isn’t the problem, check to see if the plant may have a long juvenile stage.

"Some plants, such as a Ginko tree, may take 20 years to bloom," Tilt says. "Many of our dogwoods grown from seed may take five to seven years to bloom, and then they bloom lightly. Many plants go through an aging process and have to mature into their sexual stage of development. One reason clones or cultivars of plants are selected, such as Cherokee Princess or Barton’s White dogwood, is that they bloomed at a very early age. So if your plant isn’t blooming yet, it may just still be too young."

Too much shade is also a common problem for poor blooming. Fast-growing trees may have taken the spotlight off your prized plant, Tilt says, resulting in fewer blooms each year.

"A full-sun plant, such as a rose, needs at least six hours of direct sun each day to offer its best flowering," he says. "The weather can cause many problems. It can be too cold or not cold enough. It can be too wet or too dry. Both extremes can cause flowers not to form or to abort."

Late pruning can also remove flower buds. Azaleas and most other early spring flowering plants form their buds after they bloom the previous summer.

"If you prune these plants, be sure to do it after they bloom," Tilt says. "Do not wait until winter. Hard rejuvenation pruning, where you cut a plant back to the ground, can also reduce or eliminate flowering. The plant becomes so vigorous that it produces excessive vegetative growth and does not slow down to set the flower buds."

At the other extreme, there are some plants that may face reduced or loss of blooms as they mature.

"They may get cluttered with old large canes like nandina," he says. "If you remove one-third of the old canes each year, as well as dead, dying and diseased branches, you will stimulate new growth with more flower buds."

Excessive vegetative growth can be caused by too much fertilization. Gardeners sometimes try to fertilize their plants into flowering with excessive amounts of nitrogen, Tilt says. As with hard pruning, the extra nitrogen forces too much lush, vigorous growth and flowers do not develop.

It may take a few years for the plant to get back to normal, he says.

"Try to soil test every few years, and follow the recommendations on the report," Tilt says. "Contact your local county Extension office for help on taking your soil test. Your soil test can help you add what is needed for your plants in the right amount. Enjoy your spring flowers, but remember it’s possible to kill them with kindness. Your flower duds may be Mother Nature’s normally abnormal extremes, or it may result from your tender loving care."

SOURCE: Dr. Ken Tilt, (ktilt@aces.edu), Alabama Cooperative Extension System Horticulturist, (334) 844-5484