Although some plants described as “weeds” can coexist with other plants in a lawn or garden without causing damage, most weeds harm cultivated plants in a wide variety of ways. Some visually attractive weeds, such as dandelion (Taraxacum officinale), purslane (Portulaca oleracea), ragweed (Ambrosia artemisiifolia), horsetail (Equisetum arvense) and bull thistle (Cirsium vulgare), aren’t worth keeping around for this reason. Weeds also become more difficult to remove as they grow out of control. Consider the following:

Plants That Harm a Landscape

1. Weeds outgrow nearby plants: 

As weeds grow in your lawn or garden, they take over the spaces between your carefully chosen plants and then spread to spaces that cultivated plants normally occupy. Most weeds have a fast growth rate. They can even spread out underground far more rapidly than what you see above ground. When this happens, cultivated plants fail to grow at their normal rates because they don’t receive enough water, light and nutrients. Weeds that spread rapidly above ground like Japanese honeysuckle (Lonicera japonica) and Devil’s Tail or Mile-A-Minute (Persicaria perfoliata) harm nearby plants by blanketing them quickly with foliage. Many weeds also produce a high volume of seeds that can stay dormant in the ground long after they drop. The Giant Hogweed (Heracleum mantegazzianum), a biennial exotic plant from the carrot family originally introduced to the United States as both a soil erosion and an ornamental plant, can disperse 20,000 to 100,000 seeds per plant after flowering depending on the size of the plant. Worse yet, the seeds can remain dormant for approximately 15 years.

2. Weeds behave like parasites:

Every plant in a garden again needs a specific balance of water, light and food to thrive. Weeds usually take over the environment quickly to such a huge extent that they prevent garden plants from having access to resources. As they grow larger and spread, weeds use up the water and nutrients in the soil that your plants need to stay healthy. Although the result of this parasitic behavior varies based on the type of weed and the nearby plant species, weeds can cause one or more of your plants to become permanently twisted, stunted, discolored, diseased or withered and can introduce a bacterial, fungal or an insect infestation. They can also make it hard for your cultivated plants to flower and produce fruits and seeds. In addition, some weeds kill a plant through parasitic behavior by directly attaching to the plant’s roots, stem or branches and consuming all of its nutrients. 

More Than a Lawn and Garden Nightmare

1. Weeds can set off allergies and sensitivities:

As with any plant, weeds create pollen and scents that can adversely affect people who have allergies and sensitivities and those who never had a problem before exposure. Some weeds also have sap, thorns and tiny hairs that cause reactions. Ragweed pollen, for example, can cause wheezing in people who don’t normally have asthma. Some people who have certain types of food allergies can have the same reactions to certain weeds because their immune systems can’t tell the difference between the plant proteins. For example, a person with a banana, cucumber, melon or sunflower seed allergy is more likely to react to ragweed. Even if the food allergy is mild, they might experience worse symptoms if they’re exposed to ragweed around the same time they ingest one of these cross-reaction foods. You can also have a wide range of skin reactions to various weeds, such as spot and spread rashes, itching and blistering.

2. Weeds can cause various severe injuries

Many weeds are toxic. As a result, some toxic weeds that grow too close to a water source can poison drinking water. If a healthy adult touches or eats these weeds, they can become extremely ill or possibly die. The elderly, small children and pets are at higher risk of experiencing injury when exposed to certain types of weeds. Additionally, some weeds cause extreme burns. For example, the sap of Giant Hogweed can cause chemical burns that worsen with exposure to the ultraviolet part of sunlight. The plant can grow as tall as 15-feet high and four inches across. Its roots spread quickly through the ground. Although it looks beautiful and shares a similar white flowering top as Queen Anne’s Lace (Daucus carota) and Poison Hemlock (Conium maculatum) on a much grander scale, common exposure injuries include painful rash, blistering and swelling and permanent purple marks and scars. Depending on the amount of exposure, Giant Hogweed’s sap can even cause temporary or permanent blindness. 

Top Weed Prevention Measures

1. Physically remove the weeds:

You can prevent seed dispersal and overgrowth if you remove weeds from the soil as soon as you see them. Removal of new growth also reduces the amount of time and effort that’s usually necessary to remove a full grown plant. Keep in mind that you should always pull and dig with your hands as much as possible to prevent above- and below-ground damage to your cultivated plants. If you need to use garden tools to dig up a weed, such as when trying to dig up a bull thistle that has a thick or long taproot, always perform the task as carefully as possible.

2. Cut the tops of weeds:

If you don’t have time to pull weeds on a regular basis, cut off the flowers and seed heads instead to slow overall plant growth and spread. This action also helps reduce the amount of new growth next year. To cut weeds after mowing your lawn, mow again with the mower blade set to a higher position than the height of your grass. In your garden, use a trimmer or pruning shears to handle individual plants.

3. Till only when absolutely necessary: 

Tilling can bring old, dormant seeds to the surface where sunlight and the right conditions can cause them to sprout a new generation of weeds all over your lawn or garden. Till only when you need to introduce air, organic materials and nutrients into a garden bed. Since dormant seeds don’t begin to germinate until you bring them to the surface, never disturb soil too far below the recommended seed or seedling planting depth for different plants unless you have no other choice. 

4. Stop new growth in unused soil:

Plant all of your garden plants as close together as possible to stop weeds from spreading in open soil areas. Water your garden plants only and leave the spaces, and weeds, between these plants dry to dehydrate and kill any weeds that pop up. You can also use organic mulch between plants to stop new growth. If you live in a climate that experiences cold weather, prevent weed seeds dispersed by air and animals from growing in open areas by covering the soil entirely with organic mulch or seasonal cover crops. 

5. Use caution when handling new plants:

For your lawn, consider using sod instead of grass seed. With sod, you can see if the sod has weeds already in it. Also, not only does grass seed leave gaps in the soil that make it easier for weeds to sprout up, but birds are far more likely to accidentally transfer weed seeds from other areas to your lawn while feeding on grass seed. To guarantee that you have removed any tiny seeds from weeds sticking to newly purchased cultivated plants, rinse the plants under lukewarm water thoroughly before planting them.

It’s important to remember that the act of simply removing a weed from the ground or a garden box can lead to physical harm. Wear a long sleeve shirt, pants, gloves and a mask when removing weeds to prevent reactions and injuries. For more information about weed removal or other landscaping topics, check out our blog page or contact our team of lawn and garden experts.

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