The 10 Types of Weeds That Are Most Dangerous for Your Crops

Uncontrolled weeds cost a 200 bushels per acre corn farmer about $280-$320 per acre! Weeds have been tormenting farmers since the first days of agriculture.

Weeds compete (and often win) over crops for access to light, moisture, and nutrients. They may also be hosts to disease and insects.
This article will outline 10 types of weeds to be vigilant about in your fields. You’ll also learn about weed identification so you can tackle the problem before it becomes a serious problem.
Read on.

1. Field Bindweed (Convolvulus Arvensis)

Field bindweed is a perennial vine that is a persistent and hardy weed. This common weed can spread from seed or rootstock and its roots go as deep as 14 feet into the ground.

Field bindweed is difficult to eradicate because it grows a large network of lateral roots under the soil even when there is no foliage showing. These roots can last for up to 50 years in the soil before sprouting.

You’ll notice bindweed flowers during the end of spring and lasts until the frost arrives. Warm weather is the perfect climate for this weed to spread. This hardy plant can survive drought, tilling, cultivation, and herbicides. Review this handy guide to understanding herbicides.
As with many weeds, the best way to handle field bindweed is to prevent it and to take care of it as soon as possible.
Your best course of action is to remove seedlings when they are young and before they have a chance to become perennials. This is usually a month after germination.

Once your field has perennials buds, it can be much more difficult to get control of this vigorous weed.

2. Lambsquarter (Chenopodium Album)

Lambsquarter is an annual broadleaf weed that was grown for its edible leaves in the past. However, it harbors viral diseases that can spread to other plants in your garden or plot. It also removes moisture from your soil.

Vegetable and pulse crops such as beans, chickpeas, and lentils are susceptible to this weed. I Lambsquarter grows very quickly and the seeds are easily blown by the wind.

This weed is the most common weed in gardens according to the Weed Science Society of America (WSSA) and makes itself at home in the Northern United States and Southern Canada.

A sharp hoe will be your best friend in getting rid of this pesky plant.

3. Pigweed (Amaranth)

Pigweed is a hardy annual weed that reproduces through seeds. You’ll recognize this plant by its red, fleshy taproot. It springs up in early summer and loves the warm weather.

Broadleaf crops such as cotton and soybeans find this plant most problematic.
Pigweed or Amaranth wins the title of most “problematic” weed. Amaranth has evolved traits that makes it a tough competitor, especially in broadleaf crops like soybeans and cotton.

It’s best to get rid of this weed before it flowers. To prevent pigweed in your plots next year, use a winter mulch over your plot and till shallowly at the start of spring. Mulch a second time after tilling with a minimum of 3-6 inches of mulch.

4. Common Chickweed (Stellaria Media)

Common chickweed is one of the most common garden weeds that grows easily in filed crops, gardens and lawns.

This weed flowers throughout spring, summer, and fall. One plant can produce between 10,000 to 20,000 seeds. You can see why this is such a problematic garden weed.

Luckily, this plant has very shallow roots (1-2 cm deep to germinate) which allows you to remove by hoeing or pulling them out by hand if you catch it early enough.

5. Nutsedges (Cyperus)

This perennial set of weeds look like grass but are more thick and V-shaped. You can tell the difference by the set of leaves. They form in groups of 3, not 2, like grass leaves.

There is yellow nutsedge and purple nutsedge. Either way, they are very problematic for vegetable crops and can have a negative impact on harvest yields.

Usually, having nutsedges present is a sign that you have waterlogged soil or poor soil drainage.

To eradicate this weed, remove the small plant before it develops tubers. Without tubers, the nutsedge will eventually become extinct in your garden or plot. Also, fit the wet conditions that are making nutsedge growth possible.

Unfortunately, herbicides aren’t a viable solution against nutsedges.

6. Canada Thistle (Cirsium Arvense)

Canada thistle is a noxious, root-creeping perennial weed. The plant is up to 4 feet tall and reproduces from any part of the root system or from wind-blown seeds.

Canada thistle pops up in mid or late spring as rosettes. Then it spouts into shoots every 8-12 inches. Purple flowers bloom in the high summer months.

Thickets of Canada thistle crowd out forage grasses in pastures. Cattle will not graze near infestation which diminishes productivity. The weed also crowds out crops and reduces yield.

Due to its wide root network, it is a difficult weed to control. Horizontal roots can spread as far as 15 feet while the vertical roots burrow up to 15 feet deep. The seeds remain viable in the soil for over 4 years.

If you find Canada thistle in early spring, pull or hoe the first plants before they have a chance to become deeply rooted. Once Canada thistle is rooted, you can eradicate the weed by causing the plant stress.

When there are blooming flowers in summer is when this weed is most vulnerable. Then you can begin cultivation. Then, during the following season, you can grow a competitive crop like winter rye to combat the Canada thistle.

You can also control this weed by applying a safe herbicide for 2 years. You will likely have to undertake several tactics to get a handle on this weed.

7. Chinese Privet (Ligustrum Sinense)

This plant is also known as hedge privet as small-leaved privet. It came from China over 100 years ago as an ornamental plant and has caused problems since.

These semi-evergreen shrubs can grow up to 20 feet tall. The trunks often have various stems of long, leafy branches.

This plant can form heavy thickets that can invade fields. They might cause too much shade for some plants and even reduce tree recruitment. This plant can also displace native shrub species and the poisonous berries can hurt the fauna, especially insects in the area.

Seeds are spread by birds, soil movement and vegetation dumping.

Chinese privet grows practically anywhere. It can handle the cold, the sun and the shade. It can grow just as easily in wet soil as it can in dry soil.

8. Kochia (Kochia Scoparia)

Kochia is one of the most damaging weeds for various crops such as wheat and corn. It is also commonly referred to as summer cypress, burning bush and goosefoot. It can produce up to 25,000 seeds once it reaches maturity.

It can be detrimental to wheat yields. Just 21 plants in a square foot of land can lower yields by 1/3. Kochia can choke out broadleaf crops for both sun and access to moisture. it can grow up to 6.5 feet tall to compete with corn.

Peas and lentils are particularly susceptible to kochia because these pulses can get tied up with the weed. This makes it difficult to harvest the crop.

Kochia is also toxic to livestock. Be careful that it is not more than 50% of your cattle’s diet.

The good news is that the seeds don’t live long in the soil. You can get control of this weed situation in a year.

9. Green Foxtail (Setaria Viridis)

This weed has many names: bottle grass, pigeon grass, green bristlegrass, wild millet, and green millet. No matter what you call it, it is a big concern for farmers.

Green foxtail is registered as a noxious weed in 46 States. It is an annual plant that has a good root system that doesn’t need much to flourish.

This weed can produce up to 500 seeds per head. And there are up to 10 heads per plant. You can see how this plant can quickly get out of control.

For weed identification, first, you’ll first see a single, small green leaf that runs parallel to the ground when it pops up in spring. Some might confuse the plant with another cereal. One sign that it is green foxtail is little fibers where the lear and stem meet.

At maturity, the plant head has a bristly panicle. This plant will develop slowly in dry conditions, making them good targets for concentrated chemical weed killer.

Tall crops such as barley, durum, and canola can stand a chance against this weed. If you have a foxtail infestation, winter wheat and fall rye can help.

10. Ragweed (Ambrosia Artemisiifolia)

This common weed is an annual broadleaf that is found all across the United States. It is a hardy, difficult to control weed that can handle adverse conditions. Ragweed is an aggressive competitor with crops and is able to adapt to farming practices, making this weed a farmer’s nightmare.

There is common ragweed and giant ragweed – and both are problematic for crops.

Effective ragweed control requires season-long management. It is easiest to control ragweed when weeds are less than 4 inches tall.

Ragweed is a problem for corn and soybeans in particular because the weed blocks sunlight for the seedlings.

Final Thoughts on Types of Weeds

We hope you found this list of 10 types of weeds that are noxious for your crops instructive. As with all weeds, prevention and early action are your best defense against a weed infestation.

Check out the best weed killers for 2018.