Hydrangeas, lilacs, forsythia and other flowering shrubs add seasonal beauty to your gardens. For some shrubs, this is the main reason you purchased them and it’s disappointing when they don’t flower. Here are a couple of reasons shrubs fail to bloom and what you can do to encourage them to flower.
Spring Flowering Shrubs
Lilacs, mock orange, forsythia, bridal wreath spirea and other spring flowering shrubs form their flower buds the summer prior to spring bloom. Spring flowering shrubs should be pruned, if needed, right after flowering to maximize their spring floral display. Pruning at other times of the year won’t hurt the plant but removes some or all the flower buds resulting in very few or no blooms.
Extremely cold temperatures can kill the flower buds negatively impacting bloom. Forsythia and mock orange are perfect examples. Although the plants are hardy in our area the flower buds on some varieties are not. This is why you often see forsythia flowers appear only where the snow provided insulation from the cold. Selecting varieties noted for their hardy flower buds is important to ensure a great spring flower display.
Plants Purchased & Planted in the Past Few Years
You purchased a beautiful hydrangea, lilac or other flowering shrub in full bloom. You plant it in the right location as recommended, water as needed and mulched the soil. The next year or two the plants are doing great but they do not flower. The good news is the plant is focusing its energy on developing a robust root system instead of flowers. This is good for the health and longevity of the plant but frustrating for you. Be patient, as soon it will begin producing lots of flowers.
Applying too much nitrogen fertilizer can also inhibit flowering. Nitrogen promotes lush succulent leaf and stem growth instead of flowers. Our high pH soils have lots of phosphorous, the nutrient that promotes flowering, but it is bound to the soil and unavailable to the plants. Research found when the microorganisms released the nutrients from Milorganite it also made some of this phosphorous available to the plants encouraging flowering and fruiting.
Hydrangeas
Bigleaf, Annabelle-types and panicle hydrangeas are filling our landscapes. Maximize flowering based on the species you are growing. Annabelle-type and panicle hydrangeas flower on new growth. They form their flower buds the same year they blossom. Bigleaf hydrangeas form their flower buds on the previous season’s growth. Since these often die to the ground they do not flower. The repeat blooming bigleaf hydrangeas, like the Endless Summer series and others, also flower on the current season’s growth. If the plant dies back to the ground or you prune heavily it will not flower early in the season but should flower later on the current season’s growth. Many gardeners have been disappointed when these plants fail to produce any flowers. Fertilizing in the spring and keeping the soil slightly moist throughout the growing season seems to encourage flowering. Once again I have found that Milorganite’s non-leaching phosphorous and influence on making phosphorous available to the plants promotes flowering in these plants.
Understanding how plants grow and the care they need reduces maintenance and increases their health and beauty. Always check plant labels, ask the team at Pasquesi’s for advice and look to reliable sources to increase growing and flowering success.
Written by, gardening expert, Melinda Myers. Melinda Myers is a nationally recognized gardening expert with more than 30 years of horticulture experience. She is a wealth of knowledge and we are pleased to share her articles with you!
