Everything You Need To Know About Grassy Weeds

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crabgrass bunch growth (1)

Lawns in Louisiana are prone to drainage issues and excess moisture, which means lawn weeds are almost a certainty! Being a homeowner in our region means you will have to regularly tend to your lawn, and knowing how to tell the difference between grassy weeds and healthy turfgrass is a large part of that work. Grassy weeds may look harmless, but they will leave your lawn looking sickly and unattractive. Brothers Lawn Service has put together this guide to grassy weeds to make sure this doesn't happen to your lawn this season. Let's learn all about these turfgrass impersonators and how you can stop them!

What Are Grassy Weeds?

Nutsedge in lawn

Grassy weeds are usually members of the Poaceae family, which is the same family that comprises healthy grass species. This classification is what makes grassy weeds so difficult to detect in your lawn. In the simplest terms, grassy weeds are types of grass that grow where they are not wanted. The reasons you would not want grassy weeds in your lawn are apparent as soon as you see the damage they cause. Grassy weeds tend to have fibrous, invasive roots consisting of rhizomes, stolons, and tubers. These roots spread out quickly under the soil surface and can easily overtake the healthy roots of your turfgrass. As a grassy weed invasion spreads, these aggressive roots get first access to nutrients in the soil, leaving your lawn undernourished and weak. Before long, your lawn will become a patchwork of bare spots and unattractive weeds.

Identifying Grassy Weeds

identifying goosegrass

Any plant that is considered a grassy weed is going to be difficult to identify in a lawn because of how similar they look to turfgrass. While some grassy weeds may have thicker leaf blades or stems than the grass in your lawn, other weeds may simply be a different type of "healthy" grass growing in the wrong area. For example, Bermudagrass is used as turfgrass in warm climates like ours, but it could be considered a weed if it found its way into a cool-season lawn in northern regions of the country. Grasses that grow in areas they are not acclimated to will behave differently (aggressive growth, more nutritional needs, etc.), which will disrupt the normal growth cycle of the existing grass in a lawn.

Luckily, there are ways to differentiate the grass in your lawn from an undesirable grassy weed. It may sound overly simple, but all you really need to do is search for different-looking grass blades. Spotting the differences may require more than a quick glance, but grasses (and grassy weeds) come in all kinds of different shades, shapes, textures, and heights. Grassy weeds will cause your lawn to look uneven and patchy because there will be areas of taller and/or different-looking grass compared to the surrounding turfgrass. As long as you have a keen eye when you are out in the yard, identifying grassy weeds should be no problem!

Look For These In Your Lawn:

  • Taller growth than the surrounding grass
  • Quicker growth rate
  • Brighter, green leaf blades
  • Different leaf shapes (rolled, pointed, etc.)
  • Discolored or thin patches in your lawn
  • Prominent seed heads
  • Shallow, invasive roots
  • Bunching or clumping growth pattern

Causes Of Grassy Weeds

identifying garden mums

As previously stated, grassy weeds have insidious roots that will crowd out and wrap around healthy grass roots. Some weeds spread via stolons above the soil surface, which often sprout new shoots at the nodes of the plant, and similar activity can happen below the soil surface via rhizomes. Most grassy weeds develop seed heads that can produce thousands (if not hundreds of thousands) of seeds in a single season. These seeds get dispersed by physical contact, animals, water flow, or even just a strong gust of wind. Seeds can travel long distances, meaning that a grassy weed invasion can happen at any time, even if there are no weeds currently in your lawn.

Unfortunately, the most common causes of grassy weeds are related to improper lawn care techniques. Grassy weeds seek out lawns that are already struggling because those lawns will be easier to invade and overtake. Lawns with excessive levels of nitrogen (including fertilizers) and moisture are prime real estate for grassy weeds, and these conditions can develop very easily if you are not careful.

Common Sites Of Grassy Weeds:

  • Shady spots in a yard
  • Areas with poor drainage
  • Overly fertilized lawns/soil
  • Compacted lawns
  • Near sprinkler heads
  • Underneath trees & shrubs
  • Untended borders & beds
  • Generally struggling lawns

Life Cycle Of Grassy Weeds

Some types of grassy weeds only live through one season, while others are capable of reappearing in your lawn for several years. After a seed finds its way into the soil on your property, it will begin to germinate and go through photosynthesis to attain the proper level of nourishment for growth. Once the root structure of the weed is established, it will begin to produce leaves and start competing with nearby grass for resources. During this stage, weeds will sprout new shoots and produce more seeds in order to reproduce and invade other areas, starting the cycle over again.

Annual Grassy Weeds

goosegrass seedhead

Annual grassy weeds are plants that complete their life cycle within one year. They tend to have a short germination period and can quickly invade a lawn, growing rapidly in the warm months before dying off in winter. Most annual grassy weeds produce seeds that are dispersed every season and remain dormant in the soil until the right conditions are present for germination. These plants tend to thrive in areas with ample sunlight, fertile soil, and plenty of water. Winter annuals (often misidentified as biennials) will even go dormant in the cold months and attack your lawn as soon as spring arrives, well before your lawn even has a chance to get established. These plants only survive for one season and do not have enough time to develop overly complex root systems. For this reason, seed dispersal is the main way annual grassy weeds spread.

Common Examples:

Perennial Grassy Weeds

Sedge Grass Weeds

Perennial grassy weeds, on the other hand, may live for two or more years, and they can often thrive throughout multiple seasons. While some perennials can survive unfavorable conditions, such as drought or freezing temperatures, others prosper under more favorable conditions with adequate sunlight and moisture. Perennial grassy weeds often reproduce by using underground root systems to spread from one area to another, sometimes over great distances. Surviving through multiple seasons means these weeds have more time to develop roots (even deeper tap roots), tubers, and runners all across your lawn. In addition to spreading by rhizomes and stolons, perennial grassy weeds can also produce seeds; however, this is usually a secondary method of reproduction. The strong, invasive roots of perennial grassy weeds are the real troublemakers!

Common Examples:

  • Nutsedge
  • Quackgrass
  • Bermudagrass
  • Nimblewill

Removing & Preventing Grassy Weeds

lawn fertilization example

Removing mature grassy weeds can be challenging, mainly because it is hard to treat them without damaging your lawn. Pulling up or digging out grassy weeds is not always the best choice because small fragments of plant matter left in the soil can sprout new growth. Weed killers can be used, but they must be applied very carefully when dealing with grassy weeds. Non-selective weed killers (like glyphosate) work best on grassy weeds, but they can not differentiate between healthy and unhealthy vegetation. Accidentally applying non-selective weed killers to your lawn will cause your grass to die, leaving your lawn open for another weed invasion in the future.

Preventive lawn care is always the best choice for controlling grassy weeds. In the Baton Rouge and Lafayette areas, you can always call a professional like Brothers Lawn Service to take care of your grassy weed problem! To prevent grassy weeds from ever taking hold in the first place keep the following tips in mind:

  • Fertilize Properly - Too much nitrogen in your lawn is a common cause of grassy weeds, which is why fertilizing properly is so important.
  • Water Deeply - The shallow roots of grassy weeds get first access to water, so longer watering sessions give your lawn a chance to hydrate.
  • Mow High - Allowing your grass to grow slightly taller than normal can help crowd out any weed seedlings that try to emerge.
  • Aerate Compacted Soil - Aeration decompresses compacted soils, which allows your lawn to thrive and crowd out harmful weeds.
  • Use Mulch - Mulching your garden beds and soil can help to reduce the spread of grassy weeds by preventing them from emerging.
  • Apply Pre-Emergent - Pre-emergent is best applied in spring when young seeds are still germinating. Call Brothers today to safely and effectively apply pre-emergent this spring!