Crabgrass is a group of weedy grasses that grow everywhere. Like any other weeds, crabgrass is undesirable yet can easily spread due to its fast growth and tendency to spread aggressively.
Highly adaptive and less demanding, crabgrass tends to grow anywhere. If you are dealing with crabgrass in your area then this guide will help you confirm them and take proactive steps to control their spread.
Details About Crabgrass
Crabgrass is an annual grass weed prevalent in temperate and tropical regions worldwide. As they prefer warm climates, the germination of the crabgrass often starts in late spring or early summer.
When the temperature falls below 50°F (10°C) during winter, it stops growing and completely dies off with the onset of the frost.
Lifecycle
As the warmer months arrive, the dormant seeds present in the soil start to germinate. As crabgrass is highly adaptable, it germinates in any condition including drought, heat, and poor soil fertility. You can find them thriving in every kind of space such as sidewalks, driveways and garden edges.
If not removed in time, crabgrass can grow throughout the season. They grow rapidly and vigorously forming dense mats even in scarcity of nutrients and moisture and can each height of several inches to over a foot tall.
Later in life, they develop erect stems with seedheads. Before dying, the seeds from the seedheads are released into the surroundings which are capable of remaining viable for several years.
Except for roots, crabgrass can be identified based on their body parts. Mature crabgrass possesses the following structures: stems, leaves, reproductive structures and seedheads.
Stem
The stems of the crabgrass generally remain close to the ground and only grow a few inches. During the development, the stems lie horizontally to the ground and become upright upon maturation.
A group of stems forms a rosette-like structure. As the plants mature, vertical stems emerge out of these rosettes. During the reproductive phase, the stems produce seedheads.
Leaves
The appearance of the leaves is the most prominent feature to distinguish the crabgrass. With flat and wide blades, the leaves resemble other popular grass species like Bermudagrass and centipedegrass. The length and width ratio of this grass is approximately 2:1 to 4:1.
Leaves grow alternately along the stem rather than directly opposite to each other. The leaf's margin and color however varies from species to species. Margins can range from smooth to serrated and color can vary from light green to purplish-red. The young leaves are lighter in color and older leaves may have different colors also based on sunlight exposure and other environmental conditions.
Seedheads
Seedheads are the primary reproductive structures of crabgrass. A seedhead grows on the stem during the maturation phase and can produce anywhere from several dozen to several hundred seeds. Seedheads contain clusters of tiny flowers, each bearing reproductive organs necessary for seed production.
The flowers are pollinated by wind which if successful gives rise to seeds. Once mature, the seeds are released into the environment. Their light weight allows them to be easily carried over long distances, making their establishment in new places easier.
Reproductive structures
In addition to seedheads, different species of crabgrass also contain other reproductive structures. Nodes, runners and tillers are some other structures that play an active role in the spread of crabgrass.
Nodes play a crucial role in the plant's growth. Node helps crabgrass to develop both shoot and root, hence aiding in the horizontal establishment above the ground. Runners also known as stolons are above-ground horizontal stems that help send out roots and shoots at intervals.
Tillers are also found in some crabgrass which are lateral shoots emerging from the base of the plant. They can develop into new stems and leaves helping in the plant's expansion. The tillers look like crab legs, that's where the grass gets its name from!
The most important to stop the establishment of crabgrass is to prevent it from spreading. The following measures can be adopted to prevent their spread:
Maintain a thick lawn
If your place has a thick lawn then there is a minimal chance of crabgrass infestation! A thick lawn makes sure that the soil is getting enough shade hence keeping the soil temperature cooler. As we have already mentioned, crabgrass needs warm soil for growth, this trick will definitely keep the crabgrass away.
Moreover, a well-established turf also has healthy roots. They can easily compete with crabgrass for water and nutrients. By doing so, they can outcompete crabgrass and prevent crabgrass seeds from germinating.
2. Cover all the bare spots
To prevent any bare spots in your lawn, just overseed it with your favorite grass's seeds. Overseeding leaves no room for crabgrass seeds to germinate and grow.
The physical barrier provided by the so-formed turf prevents crabgrass seeds from reaching the soil and germinating. Overseeding not only deters the growth of crabgrass but also makes the lawn look attractive.
3. Stop frequent watering
Shallow and frequent watering allows the soil surface to become constantly moist. This situation is ideal for the germination of the crabgrass seed. So to prevent this, allow the soil surface to dry out between waterings.
As the crabgrass has shallower roots, contradictory to the turfgrass species, their roots are able to absorb only surface water. So infrequent deep watering favors the growth of turfgrass whereas the further growth of crabgrass will be halted in this situation.
4. Mow at right height
Mowing not only helps to maintain a healthy lawn but also helps to prevent crabgrass infestations. This process helps to maintain a thick canopy that shades the soil surface. This inhibits sun rays from reaching the soil surface making germination of crabgrass seeds impossible.
A taller mowing height helps conserve soil moisture by providing shade whereas if it is too short or if the lawn areas get scalped, there is a high possibility of successful germination and growth of crabgrass.
5. Pre-emergent herbicides
If your area was previously infested by crabgrass, pre-emergent herbicides can be a valuable tool for you. As the seeds of the crabgrass can remain viable for a long time, previous crabgrass plants may have left behind seed banks in the soil that are ready to germinate.
To prevent them from germinating, apply pre-emergent herbicides in thin or bare spots in the lawn, along edges, or in areas with poor drainage. As the spring begins and the soil starts to warm up, apply these herbicides to prevent crabgrass seeds from germinating and establishing before they become a problem.
How To Kill Crabgrass?
There may be chances of growth of crabgrass even though you have tried all the preventive measures, all thanks to their viable seeds!
For already spread structures of crabgrass, the following steps will help you clear them in the most efficient way:
Hand-pulling
This manual method does not rely on the use of chemicals. As you identify crabgrass and distinguish it from the desirable turfgrass species, you can remove it by choosing the right time.
Hand-pulling is best done after rainfall or watering. During this time, the soil is moist and the entire plant can be removed without the possibility of remnants.
It's necessary to remember any small fragment left behind can lead to regrowth. Also, disposal of the crabgrass should be done mindfully to prevent further growth.
Chemical control/ Post-emergent Herbicides
If the crabgrass has gone out of hand, then there is no better method than applying the chemical methods. Herbicides formulated to target crabgrass are available that can selectively eliminate crabgrass from your space.
Post-emergent herbicides work quickly and are efficient in controlling actively growing crabgrass. Liquid sprays and granular forms are some of the available formulations for straightforward application.
It's best to apply these herbicides timely to prevent further infestation and minimize damage to desirable grass species.
There are many varieties of crabgrass worldwide. Among them, smooth crabgrass and rough crabgrass are widely prevalent. All of the varieties of crabgrasses that cause problems for lawns in various parts of the world are mentioned below:
Smooth crabgrass (Digitaria ischaemum)
Smooth crabgrass is a summer annual grass native to Europe and Asia. This variety of crabgrass reaches a height of about 6 inches. The distinguishing characteristic of this crabgrass is its smooth and hairless leaves and stems.
The leaves are blades of this variety are relatively wide and may have a slightly folded or V-shaped appearance.
The stem lacks the rough texture often found in other crabgrass species. These crabgrass are widely adaptable and its seedheads are relatively inconspicuous compared to some other crabgrass species.
Hairy crabgrass (Digitaria sanguinalis)
Hairy crabgrass is another prevalent variety of crabgrass. This variety is native to Europe and is taller than the smooth crabgrass (reaches a height of up to 2 feet). The stems and leaves of this crabgrass are hairy, which separates them from the smooth variety.m
The hairs can be seen on both sides of the leaf sheaths and can even extend onto the leaf blades. The hair present on the leaves and stem also provides them with a slightly rough texture.
Southern crabgrass (Digitaria cilaris)
Southern crabgrass is native to the United States. The distinguishing characteristic of this variety is its long and hairy leaves. The leaves are broader compared to the other varieties giving them a distinctive appearance. Both sides of the leaves are covered with hair giving them a rough texture.
The stems of the southern crabgrass are hairless and may appear glossy when they are young. The seedhead of this variety is slightly larger compared to other crabgrass species.
Others
Several other varieties of crabgrass also exist. Blanket crabgrass is one of the less prevalent varieties that is highly invasive. Indian crabgrass is another native to India. Several other varieties are also present named after their locality.
Texas crabgrass, Carolina crabgrass and Madagascar crabgrass are some examples if such varieties.
