Crabgrass (Digitaria spp.) is one of the most notorious weeds, particularly for lawn enthusiasts, due to its aggressive growth and ability to take over turfgrass. In other words, they are slender monocotyledonous pasture and forage plants.
Crabgrass has a low-growing, sprawling habit with stems that radiate outward from a central point, giving it a crab-like appearance, which is where its common name originates. The leaves are flat, smooth, and light green, often with a distinctive white or silver midrib. It produces seed heads on elongated stems, which are typically finger-like and can vary in number. The seeds are small, numerous, and easily dispersed.
It’s an annual grass, it completes its lifecycle within a year, germinating in spring when soil temperatures are warm enough, growing through summer, and dying off with the first frost. Crabgrass is also a prolific in seed production, with seeds capable of remaining viable in the soil for several years, leading to recurring issues.
Crabgrass thrives in conditions where turfgrass is stressed, such as areas with poor soil, compacted ground, or where there’s inadequate watering or mowing. It prefers warm, sunny locations and can often be found in lawns, gardens, agricultural fields, and along roadsides.
Crabgrass is highly adapted to survive in urban environments, with its seeds easily hitching rides on shoes, tires, and machinery, aiding in its wide dispersal. While now considered a weed in many contexts, plants like crabgrass have historically been indicators of soil and land use changes, showing where human activity has altered natural landscapes.
Uses
- It can be used as livestock feed, especially in regions where regular forage might be scarce. Crabgrass has reasonable nutritional value when young and can be grazed or harvested for hay.
- Its rapid growth makes it useful for stabilizing soil in areas prone to erosion, particularly where immediate vegetative cover is needed after disturbances like construction or natural disasters.
- In some agricultural or ecological restoration contexts, it might be used as a temporary ground cover to prevent weed invasion or to improve soil conditions for subsequent plantings.
- Crabgrass, like many weeds, plays a role in ecological succession, often being one of the first plants to colonize bare ground, thereby preparing the ground for other species.
Types of Crabgrass digitaria spp
The most common species include Digitaria sanguinalis (large crabgrass) and Digitaria ischaemum (smooth crabgrass), though there are several species within the genus.
Digitaria sanguinalis (Large Crabgrass)
- Leaves: Broad, flat, and light green with a distinctive white or silver midrib. The leaves are somewhat hairy, especially on the upper surface and along the leaf margins.
- Stems: Stems are typically hairy, particularly at the nodes and along the upper parts. This hairiness can be a key identification feature.
- Growth Habit: It grows in a more sprawling manner, with stems radiating out from a central point, often lying flat on the ground before ascending.
- Inflorescence: Produces multiple (up to 15) finger-like seed heads on each plant, which can be quite dense. The seed heads are often a darker green or purplish.
- Seeds: Small, with rough-textured surfaces, enabling them to adhere to fur, clothing, or machinery, aiding in dispersal.
- Habitat: Prefers sunny, disturbed areas with compacted or poor soil but is adaptable to a range of conditions.
Digitaria ischaemum (Smooth Crabgrass)
- Leaves: Similar in shape to large crabgrass but generally smoother without the pronounced hairiness, though some fine hairs may be present. The leaves are also light green with a midrib, but often less pronounced than in large crabgrass.
- Stems: Distinctly smoother than large crabgrass, with less or no hair, which is a useful trait for distinguishing between the two species.
- Inflorescence: Typically has fewer (3-5) and shorter seed heads compared to large crabgrass. The seed heads are more open and less dense.
- Seeds: Similar in size and texture to large crabgrass but might be slightly fewer in number.
- Habitat: Also favors disturbed sites but can sometimes be found in slightly shadier conditions than large crabgrass.
Crabgrass digitaria spp Control Methods
Preventive Measures
- Healthy Lawn Maintenance: Ensuring your lawn is dense, healthy, and well-watered can prevent crabgrass seeds from germinating by blocking sunlight to the soil surface.
- Appropriate Mowing: Mow at the right height to promote the health of desirable grasses without stressing them, which can make way for crabgrass.
Cultural Practices
- Aeration: Regularly aerate the lawn to reduce soil compaction, which can inhibit crabgrass growth.
- Fertilization: Use appropriate fertilizers to promote the growth of competitive grasses and plants.
Chemical Control:
- Pre-emergents: Applied in early spring before soil temperatures reach the germination threshold for crabgrass seeds. This creates a barrier that prevents germination.
- Post-emergents: Used once crabgrass has begun to grow. These herbicides must be selective to avoid harming desirable grasses.
Mechanical Control
- Hand Pulling: Effective for small infestations, though it must be done carefully to remove the entire plant to prevent regrowth from root fragments.
- Hand Tools: Specialized tools like weeding knives or crabgrass pullers can facilitate removal.
Biological Control
- While not a common approach, some insects and diseases can affect crabgrass. However, using biological control agents in residential or controlled settings is less practical due to the risk to other plants and environmental considerations.
Other Tips
- Timing: Understanding the lifecycle of crabgrass is key. Applying pre-emergent herbicides too late can miss the germination window, while applying too early might not provide protection through the entire germination period.
- Integration: The most effective approach often involves integrating several methods. For example, using pre-emergent herbicides coupled with proper lawn care practices and spot treatments with post-emergent herbicides for any breakthrough.
- Observation: Regularly monitor your lawn for signs of crabgrass emergence to catch it early when control is easier.
Crabgrass digitaria spp medicinal uses
- Crabgrass seeds are nutrient-dense, offering protein, vitamins, and minerals like calcium, magnesium, and phosphorus.
- In various cultures, particularly in traditional Chinese medicine, it’s used for treating summer heat, fever, and as a cooling agent.
- Direct application of crushed leaves has been suggested for quick relief from skin irritations, bites, or minor cuts due to its soothing and possibly antimicrobial properties.