All About Weeds
What is a weed? The simple answer is any plant that is growing in your lawn that you do not want there. Some plants are desirable to some homeowners and totally undesirable to others. For example, Fescue is the predominate grass used in Missouri lawns and is a very desirable choice for this area. However, if you have a Zoysia or Bluegrass lawn and Fescue grass is coming up through the Zoysia or Bluegrass, the fescue then becomes a weed since the homeowner does not want it in his lawn.
Generally speaking, there are three categories of weeds that we become concerned with in Missouri lawns: Broadleaf weeds, Weedy grasses, and Sedges. Each of these weeds must be controlled in very different ways. Also, seed from these weeds can be transported in at least three different ways. When the seed pods mature, the seed can be blown over a large area by winds. Birds also eat the seeds and deposit their feces containing non-digested seed in a lawn many miles away. Floods also play a role in the transportation of seed from one area to another.
Broadleaf weeds can be identified by the leaf of the plant. Leaves are generally broad and short as opposed to a grass leaf which is generally long and narrow. Broadleaf leaves also have predominant veins on each leaf. There are many broadleaf weeds that can show up in a lawn each year. However the two broadleaf weeds that cause homeowners the most grief in Missouri are Dandelions and Clovers. Winter Annuals are also a concern of many homeowners.
Dandelions are the most difficult weeds to control in a lawn. What makes Dandelions so difficult to remove from a lawn? Well, Dandelions enjoy the best of both worlds. Above ground, their seeds ride the wind currents poised to drop into the slightest opening in your lawn to propagate the species. Below ground, they put down a taproot up to 10” long. Pulling the taproot as a means of Dandelion removal is very problematic. Thick but brittle, the taproot easily fractures, and if any of the taproot remains in the ground it will regenerate. Therefore, it is not advisable to try pulling this weed. Another problem with the Dandelion is the fact the seed may germinate at almost anytime. Most seeds germinate in the spring, but Dandelions can also germinate into the fall making most chemical treatments a challenge.
Most pre-emerge applications used in the spring are not effective on Dandelions as they only carry a “suppression label” at best. The reason is these pre-emerge applications are designed to keep unwanted grass seed from germinating which can be a much more severe problem than the Dandelion. Also, pre-emerge chemical treatments for broadleaf weeds in the spring are not very practical due to their higher cost, plus they will have zero effect on killing the taproot of Dandelions already in the lawn. Therefore, in the first application, most lawn care companies apply a pre-emerge application to keep problem grasses from germinating. The second application will consist of a contact weed killer that is designed kill any broadleaf weeds in the lawn.
Clover is one of the more common weeds found in North America. White and Red Clovers are the most common species we see in Missouri. Clover is a rare weed, in that most people want to get rid of it when it invades their lawn because it is a deeper green and not the same height as the rest of the lawn. It also tends to grow in patches and will crowd out the grass in the patch. However, clover does have some very positive benefits most people do not realize. Clover provides healthy nitrogen to surrounding grass since it manufactures its own, which is why it is always a dark green color. Clover also attracts pollinators to your yard; is disease resistant, and drought tolerant.
The most effective way to eliminate Clover is to apply a contact weed killer that will not damage the grass and is labeled for Clover. Since Clover leaves have an oily film on the leaves, it may be necessary to incorporate a spreader sticker with the contact weed killer in order to get maximum kill of the plant. Also, more than one application may become necessary to totally eliminate the Clover patch.
Winter Annual weeds germinate in the fall or winter, grow during any warm weather which may occur and otherwise remain somewhat dormant during the winter. They resume growth in the spring, produce seed and die as temperatures increase in late spring and early summer. They quickly invade thin turf areas especially where there is good soil moisture. Shade may also encourage growth. Many have a prostrate growth habit and are little affected by mowing. For example, under close mowing, common Chickweed will survive, forming dense patches which crowd out the desirable turfgrass. Frequent watering also encourages Chickweed growth. Two other types of winter annuals found frequently in Missouri lawns include Henbit and the False Dandelions.
As stated above, if left alone, the winter annual plant will die when it starts to get hot in the spring or early summer. However, if you desire to eliminate winter annuals, the most effective way is to apply a contact weed killer in the early spring, since a broadleaf pre-emerge is not practical or cost effective. Central MO Turf Management’s second application is very effective for this purpose.
Weedy grasses can generally be identified by the leaf of the plant. The leaves of weedy grasses tend to be long and narrow as opposed to broadleaf weed leaves which are short and wide. There are literally hundreds of weedy grasses that can visit your lawn each spring. However, the most common problem in Missouri and many other areas is Crabgrass.
The lawn weed, Crabgrass is a warm-season annual weed which means it reproduces by seed. People often ask how to kill this pesky weed. The short answer is by applying pre-emergent herbicides at the right time in order to keep their seed from germinating. To get rid of Crabgrass, one should know its lifecycle. When spring soil temps (at a depth of 2” – 3”) reach 55-60 degrees Fahrenheit, the first Crabgrass seed will germinate. From mid-summer to fall, crabgrass produces seed. The crabgrass plants, but not the seeds, are killed by autumn frosts.
As the name suggests, pre-emergent herbicides kill Crabgrass at a specific time: Before its seedlings emerge! Timing is of the essence when applying a pre-emerge product as it must be applied and watered into the soil by either natural rains or irrigation prior to the soil temperature reaching 55-60 degrees. There are many pre-emerge herbicides on the market and all come in either a liquid form or a dry granule. Some are expensive, but are effective for several weeks and possibly a few months. Some can only be purchased and applied by a licensed professional. Others are cheap, can be purchased locally, and are effective only for a short period of time. Central MO Turf Management uses a product that is rated as one of the best in the industry and has an effective range of up to three months. Some lawn care companies try to cut costs by purchasing a cheaper product with an effective range of as little as 21 days. It then becomes necessary to apply two applications to their customer’s lawns, resulting in an extra application to pay for each year. Crabgrass can also be killed with a post-emerge contact treatment. However, they are only effective in killing young small plants which are difficult to see in the lawn. Therefore, they are not very effective as a control product.
Best practices when using pre-emerge products
- Always follow label directions and apply the proper rate. Measure the lawn area and calibrate your spreader carefully.
- Irrigate after an application if rain is not emanate. Water activates the herbicide.
- Crabgrass seedlings do not all germinate at once! Therefore, either use a long effective range product or definitely apply the application at least twice in order to kill later germinating Crabgrass.
Once a pre-emerge herbicide is activated into the soil, imagine a micro-thin coating or barrier covering the soil. When Crabgrass seed starts to germinate, they touch the barrier and are killed. Therefore:
- Do not dethatch or aerate the lawn after applying pre-emerge herbicides. These activities should only be accomplished in the late fall because they will break this barrier and allow seeds to emerge if done earlier.
- Do not use a weed eater in the vertical position as this activity will also break the chemical barrier.
- Do not wear spiked or high heel shoes in the lawn as they will punch holes in the chemical barrier. Also, avoid digging or pulling weeds in the lawn.
- Do not plant new grass seed before applying a pre-emerge as the chemical will keep the seed from germinating. When planting grass to fill small voids in the lawn, after applying a pre-emerge, scratch the soil aggressively before planting the new seed. This activity will break the chemical barrier and allow the seed to germinate. However, it will allow the potential for Crabgrass to also germinate.
There are many different weeds in the sedge family that are found in North America. However, the sedge most commonly found in Missouri is Yellow Nutsedge. Yellow Nutsedge, also called Nutgrass or Water Grass, is a warm season perennial plant that is neither a grass nor a broadleaf weed. It thrives in low spots and high moisture areas that drain poorly, but can be prolific in dryer areas as well.
Yellow Nutsedge germinates from nutlets (tubers), rhizomes, and seed which makes it a very difficult weed to control. These underground nutlets, or tubers, can remain dormant in the ground for several years before conditions become right for their germination.The stem is triangular in shape and if left uncut may grow to 2 to 2 1/2 feet tall. The leaves are yellow to green and have a distinctly shiny appearance. Leaves are 5 to 8 mm wide with a distinct ridge along the mid-vein. The leaves also taper to a sharp point. However, the most telling way to identify Yellow Nutsedge is that it grows faster than the lawn grass that surrounds it, making it easy to spot in a lawn. The plant also produces feathery, umbrella-like flower clusters on top which turn to seed in the late summer or fall. These clusters will be either yellow or brown in color.
As stated earlier, this is a weed that is hard to control. We do not recommend trying to pull this plant as you will leave the nutlet and rhizomes in the ground and more Nutsedge will follow. There is also no pre-emerge on the market at this time that will kill this weed as it germinates. Therefore, using a contact herbicide is the only way of controlling this plant.There are only two or three herbicides that will kill this weed without also killing the surrounding grass plants. A product called Sedgehammer (Manage) provides the most effective control of Yellow Nutsedge and is used by Central MO Turf Management exclusively. It will not harm surrounding grass or plants as it only targets the Nutsedge plant. It should be noted that sometimes it takes two or more applications to kill all of the Nutsedge in a lawn. Also, when spraying, the operator should only target and spray the Nutsedge plant, not the entire lawn. COST: Due to the nature and unpredictability of Nutsedge, spray applications will be in addition to all annual lawn care Programs.
FACTS ABOUT WEEDS AND HERBICIDES
Herbicides are chemicals that are designed to kill unwanted plants which we call weeds. We think it is appropriate to explain some of the facts concerning herbicides and, at the same time, dispel some of the myths surrounding them.
- Herbicides can be classified into two basic areas, non-selective and selective. Non-selective herbicides are designed to eradicate virtually anything that comes in contact with it. Roundup, by Monsanto, is the best known non-selective herbicide on the market today. At recommended rates, Roundup will kill virtually anything green by translocating through the leaves, stems, and roots to completely choke the plant and kill it forever. You would never want to spray Roundup on a dandelion in your lawn because some of the material will also get on the grass blades and they will be killed. Using Roundup in a landscape bed is also not advisable. Thanks to the miracle of modern chemistry, scientists are now capable of creating chemicals that target specific species of plants. These products are known as selective herbicides. A great example of a selective herbicide is Sedgehammer, as discussed earlier. It is specifically designed to kill specific sedges such as Yellow Nutsedge. It will not harm any other plant it comes in contact with, making it very safe to use.
- Another classification of herbicides are the pre-emerge and post-emerge chemicals. As stated earlier, pre-emerge chemicals keep seed from germinating in the soil. Post-emerge chemicals, also known as contact killers, are designed to kill weeds on contact. Roundup and Sedgehammer are just two of these products.
- One of the myths in the lawn care industry is that a chemical will kill 100 percent of the plants it is designed to kill. This is just not the case! Most chemicals on the market are designed with an effective killing rate of 90 percent of the intended target. This is why it may be necessary to make two or more applications on Nutsedge in order to kill all of it. Some of the top rated chemicals on the market today may reach 95 percent. However, there are still some cheaper chemical formulations on the market today that may have a hard time getting to the 80 per cent range. This is why, in lawn care, the consumer generally gets what he pays for. This is also why Central MO Turf Management always strives to use only the highest rated chemicals on the market today. These products are a little more expensive, but they achieve the best performance possible for our customers.
- Another area that should be understood is seed germination. Just because a plant spreads its seed around this fall, does not mean the seed will all germinate next spring or rot. We have found evidence that some weed seeds may sit in the soil for as long as 20 – 25 years before they germinate. This fact just adds to the challenge of a weed free environment.
- Finally, the absolute best way to encourage a weed free lawn is to develop a thick stand of turfgrass; keep the soil pH at desirable levels; design a fertilization program that will keep soil fertility at the optimum range; and apply necessary water when needed. Most weeds do not like to compete with a thick lawn. Also, most weeds also do not thrive well in a highly fertilized environment.
GREAT LAWN CARE IS NOT AN EVENT! IT IS THE PROCESS OF A PARTNERSHIP
BETWEEN THE CONSUMER AND HIS/HER LAWN CARE COMPANY!