What’s Wrong with My Flowering Trees and Shrubs?

This is the time of year when clients start calling with questions about why their flowering landscape plants didn’t put on a show as well as the neighbors’. This can be a very complex problem, with no easy answers.

Here are some of the most common reasons and cures for poor bloom:

  1. The flower buds were pruned off last summer or fall. Spring bloomers flower from buds that form in the previous summer. Shearing or pruning the plant at the wrong time of year strips the plant of its potential flowers. Remember it’s always safe to prune a flowering plant immediately after bloom.
  2. Fading flowers were allowed to develop fruit or seed pods. Fruiting in some plants inhibits flower bud formation for the next year. Snip out the flower clusters when they no longer look nice.
  3. The plant is “running on empty”. Years of neglect-accumulated drought stress, soil compaction and low nutrient levels can keep a plant from performing non-essential functions such as flowering. Address these problems in the right amounts at the right time of year.
  4. The plant is “shaded out”. Older landscapes often show a gradual loss of sunlight as the trees fill in and block the sun from reaching the understory. The solution here is to gradually change the landscape over the years to put in more shade-tolerant plants, or to remove or prune or limb up the trees.
  5. The new plant hasn’t settled in. If a plant has been in the ground less than 3 seasons, it may still be recovering from transplant shock. It needs time to get its roots established before it can support flowering. For larger trees, it takes about 1 year per inch of trunk diameter for the tree to be considered established.
  6. The plant didn’t get enough water. There are critical times of the year for each species as they form flower buds. For spring-blooming plants, this is in the summer. If it’s droughty and the plant gets no supplemental water, it may not be able to set buds. Pay attention to watering for summer blooming plants in the late spring and summer.

This article is adapted from Jo Mercer, Extension Educator, Horticulture, University of Delaware.