Plant growth is like economics.
Some plants are invested in the future, maintaining resources where they live in order to survive and grow as the years pass by.
And then there are weeds. Todd Crail, a lecturer in the department of environmental science at the University of Toledo’s, calls them the “penny stock guys.” They’re less patient, willing to consume any resource in their vicinity to grow quickly and disperse their seeds.
And in that aggressive desire to grow, some also see weeds as fierce competitors, at least in the short term.
“Weeds are very competitive when resources get scarce,” said Helen Michaels, researcher and professor emerita of biological sciences at Bowling Green State University. “Because they typically have only one goal, and that is to grow, flower, and leave offspring.”
Many weeds are annuals, meaning they only live for one year, according to Professor Michaels. They grow as much as they can and don’t try to preserve resources like light and moisture. They compete for any resource they can find, which allows them to grow quickly.
“A year like this is rough because the natural landscape of plants are struggling,” Professor Michaels said. “And weeds are really well-adapted at scavenging even when resources get low. They will grab what they can and turn it into new weeds.”
What is a weed?
It depends on who you ask.
Professor Michaels said many professionals and academics who work in related fields consider weeds to be non-native plants that are growing in unwanted places. However, there are some native plants that even professionals will call weeds.
More informally, weeds are “plants out of place,” according to Daniel Pavuk, a professor of biological sciences at Bowling Green State University. In this generally accepted use, whether a plant is a weed is largely subjective, and they can be native or non-native.
“We’re talking about plants that compete with plants that we desire to have in our lawns and gardens and crop yields,” Professor Pavuk said.
There are some ways to classify weeds, including by when and where they grow.
Some weeds grow in the cooler weather of early spring, and these weeds often drop their seeds and disappear.
Broadleaf weeds like dandelions also grow quickly in the spring.
Other weeds, like crabgrass, have a certain kind of physiology that allows them to use water more efficiently. They are able to grow in the hottest parts of the summer like late June and early July.
Some weeds also grow better in the later summer and fall.
Along with crabgrass, some of the most common weeds people will encounter are nutsedge, Canada thistle, pigweeds, and Johnson grass.
Disturbances in the ground or soil can create more opportunities for weeds to grow, along with environmental factors like light and moisture. That means yard work that removes grass, construction sites that create cracks in the ground, and similar disturbances create spots for weeds to start germinating.
“A lot of what this has to do with is recognizing the fact that weeds use certain environmental triggers or factors to decide that it’s a good time to sprout. And the most common one is actually light,” Professor Michaels said. “So if you do have to disturb your yard, try not to turn over too much soil because that gives a signal to the weeds.”
How to prevent weed growth
The causes of weed growth can also offer lessons for how to prevent it.
Since light is a signal for weeds, gardening or even pulling up weeds can lead to a new generation of weeds finding its way to the light.
Mulch is among the easiest and most effective solutions. Professor Michaels recommends putting down mulch immediately after weeding in a yard or home garden to prevent the light signal.
Professor Crail discussed mulch and other similar methods of “suppression” as good ways to prevent weed growth. Landscaping cloth and straw are two alternatives, and they don’t contain as many nutrients that are beneficial to weeds.
Zach Edwards, president of Black Diamond, a local garden center and lawn service, said that his company often uses mulch. He also said that pulling up weeds or mowing them down can be insufficient in preventing their growth in the long term, and even sometimes in the short term.
“You’re essentially pouring little drops of water on a fire,” Mr. Edwards said.
If mulch or other suppression methods are less preferable, there are some chemical solutions. Some of these are more harmful to the soil, surrounding plants, and the broader environment than others, so it is important to be selective if using herbicides. Many gardeners and environmentalists shun herbicides because of their negative effects.
Most chemical solutions are acid-based, and they basically burn the plants that are sprayed.
“If you are careful with how you spray, you don’t hit the foliage of your desirable plants, you can get pretty quick and easy control,” Mr. Edwards said. “And just like anything else, the earlier in the process you catch it, the better success you’ll have.”
Especially for particularly undesirable weeds, Professor Michaels said that it’s critical to tackle the smaller weed problem in order to avoid a bigger one that may require treatment with more harmful chemicals in the future.
She also mentioned that chemical germination inhibitors can be effective. Some household items, like salt and vinegar, can also be used to kill weeds.
Not all bad
There are some benefits to weeds. Since determining what plants are weeds is subjective, a plant that may be undesired in one area can still be useful and greatly desired elsewhere.
Angie Fitzpatrick, who gardens at her home in Harvard Terrace in Toledo, thinks weeds are unfairly criticized in general. Some weeds can be important for pollinators and wildlife, and others can become pretty flowers or bear fruit.
“One of the things that I’ve always tried to do is give weeds a chance, see what it is, before I rush to yanking it out,” she said.
Weeds are also sometimes edible. Plants like purslane, which many people dislike, can offer an edible and tasty snack.
As Professor Michaels said, “One person’s weed is another person’s interesting flower.”
First Published July 12, 2022, 12:00 p.m.
