Gardening Essentials: Boosting Your Blooms
You’ve done it. You’ve taken the plunge and planted a flower garden. Congratulations!
Flower gardens are all about blossoms, in whatever colors you have chosen to plant. It’s discouraging, therefore, when the plants don’t bloom to their fullest potential, whether it’s the first year after you planted them or a few years later.
Why do flowering plants fail to blossom? There are several possible reasons, a couple of which are quite common.
First, if some of the perennials (plants that live for more than two years) in your garden are a few years old or older and they’re failing to bloom, it’s possible that there have been changes in your microclimate. An area that once was sunny, for example, might be getting more shade as nearby trees or other shrubs have matured. Many of our favorite perennials, such as daylilies, daisies, roses, peonies and irises, need at least 6 to 8 hours of sun per day for maximum flowering.
It’s also possible that your plants, especially irises and daylilies, have grown into such large clumps that they are choking themselves and need to be divided. If there’s now more shade where there used to be sun, you can either prune your shade-casting trees and shrubs or move the perennials to a sunnier spot in your yard.
If your perennial plants need dividing, the general rule of thumb is to divide and replant spring- and summer-blooming perennials (creeping phlox, columbine, dianthus, astilbe, bellflowers and delphinium) in the fall. Late summer- and fall-blooming perennials (daisies, daylilies, bee balm, coneflowers, coreopsis and tall phlox) should be divided and replanted in the spring.
Beginning gardeners often ask whether quick-acting fertilizers can help plants blossom more abundantly. Well, yes and no.
Phosphate (the middle number on fertilizer labels) is required in the soil for good root establishment and flower production. When I began gardening more than 30 years ago, the common belief was that phosphorous is slow-acting and therefore it was important to add phosphate (such as bone meal or triple superphosphate 0-45-0) to the planting holes of roses and other flowering shrubs.
Even these days, if you look at the numbers on the labels of commercial fertilizers advertised as blossom boosters, you will see that the middle number (phosphorous) is always higher than the first and third numbers (nitrogen and potash).
However, recent research based on extensive soil testing, especially work conducted by Linda Chalker-Scott, an associate professor at Washington State University, has shown that in most urban/suburban soils, phosphate levels are adequate, or more than adequate, for normal plant growth.
In fact, Chalker-Scott says too much phosphorous in the soil can interfere with beneficial mycorrhizae, or root fungi (myco means fungus and rhizae means roots). These fungi colonize the root systems of plants, allowing them to absorb more water and nutrients from the soil than they would be able to on their own. In turn, the plant provides the fungi with carbohydrates that it uses as food.
Texas A&M University research on mycorrhizae over the past 25 years has shown that these little fungi can greatly enhance plant performance, even in strip-mined soil.
Research on mycorrhizae is ongoing, but results seem to indicate that adding the appropriate mycorrhizae to your garden soil can help plants thrive. What appropriate mycorrhizae for your garden might be depends on several factors. A trip to a reputable garden center can help you learn more.
So, what’s the average home gardener to do? I would recommend remembering the old adage: “Feed the soil, not the plants.” Feeding the soil can help naturally occurring mycorrhizae in your garden thrive and multiply. Feeding the soil also means cutting back on applications of nonorganic fertilizers, unless a soil test indicates a strong deficiency in some important nutrient. (UMass Amherst and the University of New Hampshire both offer a range of soil-testing services at reasonable rates.)
The most effective way to feed soil over time is to keep the area well mulched with organic matter. The mulch doesn’t have to be bark mulch. You also can mulch with compost, grass clippings from a lawn that hasn’t been chemically treated, chopped leaves and wood chips. I have used a combination of mulch materials over the years. In my more established garden beds, I do a lot of what I call “composting on-site.” For instance, when I trim rose bushes in the spring, I cut the trimmings into 3-to-4-inch pieces and leave them on the ground beneath the bushes. I do the same with the prunings from other woody shrubs, and even some herbaceous perennials, all season long.
Doing this makes sense if you think about it. What happens to all the plant material that dies and falls to the ground every autumn in forests and untended fields? Nature seems to have figured out a way to feed its soil, and the plants growing in it, without much help from us.
Photography by Adrien Bisson.