By their very nature, weeds will pop up wherever they can — including in your cherished flower beds. Here are eight ways to keep those beds weed-free.
How to Prevent Weeds in Flower Beds
Nature gives weeds one job to do: cover bare ground. That empty real estate tends to be abundant in flower beds, especially those with annuals or perennials slow to come out of dormancy and claim their territory. That’s why it’s important to limit weedy interlopers as best you can. Often, that means using more than one method of control.
“Since weeds are incredibly diverse, a variety of techniques may be necessary for best control,” says Cynthia Haynes, professor of horticulture at Iowa State University. “Mulch, hand weeding, cultivation and chemicals, when needed, are some of the best ‘tools’ in the gardener’s toolbox.”
On This Page
Till
When starting a flower bed from scratch, you must first eradicate existing weeds. One strategy is to bring out the tiller. “Tilling can be a good idea for certain areas that are ‘new’ or being redone, especially if there is a lot of weed pressure,” Haynes says. “But tilling will allow new weed seeds to germinate, so another technique may be needed afterward to complete the preparation of this new area.”
Follow-up options include mulching, applying herbicide or hoeing until the weed seed bank is reduced.
No-Till
On the opposite side of the spectrum is no-till gardening, which involves disturbing the soil as little as possible so weed seeds remain buried. Digging is restricted to the planting hole. No-till gardening works best when a layer of mulch is applied in advance.
“I love organic mulch. I use it on all of my beds and even in containers of annuals,” Haynes says. “The benefits far outweigh the potential issues. Mulch conserves moisture, so you don’t need to water as much. It prevents some weeds from germinating quickly, and makes it easy to pull those weeds that do.”
Pre-emergent Herbicide
A pre-emergent herbicide prevents seeds from germinating but has no effect on established plants. “Using a pre-emergent herbicide, like PREEN, in a flower bed in early spring will reduce weed pressure,” Haynes says. “But gardeners need to be careful, as this will only work on annual weeds. Perennial weeds that emerge from overwintering roots and stolons will not be impacted.”
Gardeners should avoid using a pre-emergent herbicide if they are growing anything from seed, including flowers that self-seed new generations annually, such as poppies, bachelor’s buttons, cleome, cosmos and zinnia.
Post-emergent Herbicide
For stubborn weeds, a post-emergent herbicide is an option. “Sometimes, these are necessary when the weeds are getting ahead of the gardener. Fortunately, the gardener can decide if they are warranted every year, every other year, or only once in 10 years,” Haynes says.
Glyphosate, found in herbicides such as Roundup, is one Haynes uses. “I like having a chemical that I can use on some of the tough weeds like thistles or woody weeds like mulberry or poison ivy,” she says. “I know that I am never going to be successful at digging out these weeds. I also know that it may take a couple of applications to be successful.” Follow label directions and all safety precautions. Avoid using it when it’s windy to avoid herbicide drift.
Fill
Open space is an invitation for weed seeds to colonize a flower bed. Roll up the welcome mat by planting annuals close together to reduce the amount of sunlight reaching the ground, which will, in turn, decrease the population of weeds.
Ground covers also perform this task, spreading quickly to cover bare ground. The trick is to pick one that won’t overtake your flowers. For example, ajuga is a less aggressive ground cover than periwinkle.
Mulch
Mulch smothers existing weeds and keeps seeds from germinating. “I like shredded bark mulch, particularly cypress, which I don’t have to add to every year,” Haynes says. “I also like the fact that as an organic mulch degrades, it is adding organic matter to my soil.”
While organic mulches like wood chips must be replenished occasionally, inorganic mulches such as stones or pebbles do not. “It is important to remember that a couple of inches of mulch is all that is necessary. Any more than that can lead to issues,” Haynes says.
Mulch Plus
Some gardeners lay down newspaper, cardboard or landscape fabric to create an additional barrier before mulching. Landscape fabric is a permeable material that smothers weeds but still allows moisture to penetrate to the ground. The fabric is pinned in place and a large X cut into the fabric where planting will occur.
Landscape fabric works best with a permanent planting of perennials or woodies rather than annuals, bulbs or ground covers. Weeds may still pop up in the mulch above the fabric but are easily removed when young.
Weed
It is important to remove weeds as early as possible, preferably after rain when the soil is soft and weeds are easier to extract. A trowel, dandelion fork or other weeding tool makes weeding more efficient.
“While I would rather just pull out weeds by hand, my husband prefers a diamond-shape weeder and sometimes a hori hori knife for tough weeds,” Haynes says. “It’s all about having multiple options in your gardener toolbox to tackle weeds as they come. I will never have a weed-free garden, but as long as the flowers outshine the weeds, I’m winning!”
About Our Expert
Cynthia L. Haynes is a Professor of Horticulture and Consumer Horticulture Extension Specialist at Iowa State University. She holds a Bachelor of Science from Louisiana Tech University as well as a Master of Science and Doctor of Philosophy from the University of Georgia. Winner of numerous awards and special recognitions, Haynes teaches classes in horticultural science, herbaceous ornamentals, and environmental and sustainable horticulture, among other topics.
