When plants won’t bloom

    One of the confusing and frustrating things gardeners sometimes contend with is a plant (often a shrub) that won’t bloom.

    Roses can be particularly annoying to figure out, as different types require different expectations. Some bloom only once, around now, whereas others will continue to bloom all summer. Still others will bloom, then take a long summer rest before pushing out another flush of flowers in the fall.

    Before humans got their hands on them, roses were like any other shrub in nature. The bloom period was a brief stage in its reproductive cycle. Today after centuries of hybridizing, their reproductive cycle is about as natural as Octomom’s. Through selective breeding, modern roses have been coaxed into ignoring the biological need to make seed before retiring, and many will continue to push out flowers for months at a time. Many older rose cultivars are closer to the natural species, and will only bloom once. If you have a rose that doesn’t bloom much, it’s good to begin by figuring out what variety it is and what its genetics will dictate.

    If your rose (or other shrubby plant) is one that should be blooming often and isn’t, there could be a couple of reasons. A lack of sunlight could be the culprit, especially in older gardens. Shade in a garden generally increases over time as plants reach their mature heights, and a plant that had once lived in eight hours of sunshine could now have less. Roses and other sun-loving plants require at least six hours a day to perform well.

    Another factor is soil fertility. Roses and other repeat bloomers are heavy feeders, and even the best plant won’t repeat bloom without regular applications of fertilizer. Once a month between April and August is the general recommendation.

    And weather also plays a part. Many plants will shut down their family parts when they are stressed by either extreme heat or insufficient moisture. You can’t do much to counteract a heatwave, but regular water will definitely help to keep flower production going.

    Shrubs that flower all season are a wonderful invention, high up on my own list of modern marvels. But they can require a bit more intervention on the gardener’s end. And actually, it’s okay that some plants only bloom for a short amount of time. We like our roses all season long, but who’d want to look at a lilac bloom in July or an azalea flower in August? That would be way too much of a good thing.

    Want a digest of WHYY’s programs, events & stories? Sign up for our weekly newsletter.

    Help us get to 100% of our membership goal to support the reporters covering our region, the producers bringing you great local programs and the educators who teach all our children.