St. Augustine Grass Vs. Crabgrass: What's The Major Difference?

Lawn care is often more complicated than many people realize. There are many invasive plants that look similar to desirable plants that you’d actually want in your lawn. For instance, St. Augustine grass and crabgrass look almost the same, but they are two very different plants.

St. Augustine grass is a turf grass that grows smoothly and evenly, perfect for lawns in subtropical and coastal areas. Meanwhile, crabgrass is an overabundant, opportunistic grassy weed that can take over your lawn. Although the two plants look similar, St. Augustine is a desirable grass, and crabgrass is an unwanted weed.

St. Augustine grass is very common in the southern United States. In fact, it’s the most widely used warm season turf grass in that area. It’s salt-tolerant and well-suited for humid subtropical and coastal areas.

Also commonly called carpetgrass, St. Augustine grass is tolerant to low moisture and extremely high temperatures. It creates a smooth, even turf, making it perfect for southern lawns. Plus, it only requires infrequent mowing, and it retains its green color longer than other types of grass.

Keep in mind that St. Augustine grass is not tolerant of cold temperatures. Therefore, if you don’t live in a warmer climate, it may not be the best choice for your lawn.

St. Augustine grass thrives in sandy soil, and it’s best to keep it tall. Experts recommend keeping it at a minimum of three inches, but at four or five inches, it’s at its hardiest.

The best time to plant St. Augustine grass is in the spring or summer, when temperatures are between 70 and 90 degrees Fahrenheit. You’ll want to plant the plugs in full sun at least 90 days before the first frost of the year.

Here’s a step-by-step guide to planting St. Augustine grass on your lawn:

Now you’re ready to dig holes for the St. Augustine grass plugs. You’ll want to dig them in a diagonal planting pattern, so that each group of four holes forms a diamond. The holes should be spaced one foot apart, and each hold should be slightly larger than the plug’s root ball.

One tip to make this step quicker and easier is to rent a grass plugging tool. Grass plugging tools are generally available at hardware stores, and they create perfectly sized holes with minimal effort.

Crabgrass is a lawn weed that’s generally considered overabundant. It’s annual rather than perennial, meaning that it doesn’t survive year to year. Instead, its life cycle is completed in one year.

However, just one crabgrass plant can produce 150,000 seeds within its life cycle. These seeds can then sit in the soil for up to 30 years before they sprout. Clearly, this is a weed that can be very difficult to control!

Unlike other grassy weeds, crabgrass has a very low profile. This means that the lawnmower blade passes over it without hitting it, making it easier for the crabgrass to survive. Plus, crabgrass has very tough stalks that hold up well against foot traffic, even in high-traffic areas.

Typically, crabgrass begins to grow in the early summer. It is a drought-tolerant weed that absolutely thrives in hot weather. In fact, it’s often the last plant on the lawn to die off. Crabgrass usually sticks around until the frosts of autumn.

Not only is crabgrass an unattractive weed, but it can completely take over your lawn! It’s capable of dominating other grasses and plants in the area. It’s a very opportunistic weed that quickly takes root in any areas of your lawn that are thin or bare.

Plus, crabgrass can also crowd out good grasses and desired plants. It’s very invasive and will compete with other plants for water and nutrients from the soil. This can make it very challenging (and almost impossible) for the healthy grass in your yard to continue to flourish.

When it comes to crabgrass, prevention is key. Be proactive and apply a crabgrass preventer or pre-emergent herbicide in the early spring. This way, you eliminate crabgrass before it even starts to take root and grow in your lawn.

Post-emergent herbicides are also an option for crabgrass removal, but it’s best to keep it from growing in the first place. One way to do this, aside from using a pre-emergent herbicide, is to maintain good lawn care.

An important aspect of lawn care is allowing your grass to grow to its optimal length. You’ll want to adjust your lawnmower blade to do this; a height of three inches or more is best. Remember, the longer your grass is, the longer its roots are. Longer roots equal less room for other plants (such as crabgrass) to grow and thrive.

A few other aspects of lawn care that can help prevent crabgrass are aerating and overseeding your lawn. Both of these practices will discourage crabgrass from taking root.

In addition, you may want to do a simple soil test to check that your lawn has proper levels of nutrients. To resolve any nutrient deficiencies you discover through the soil test, using a natural fertilizer should do the trick.

St. Augustine grass and crabgrass look similar, but they’re very different. St. Augustine grass is recommended for lawns in the southern United States. Meanwhile, crabgrass is an invasive grass weed that can take over your lawn.

Generally, crabgrass has wider blades with fold lines down the center. It grows low to the ground in a star-shaped pattern.

St. Augustine grass has slightly slimmer blades than crabgrass and grows to be much taller than crabgrass. Rather than looking rough and unkempt like crabgrass, it appears much more smooth and even.

Related Questions

Is St. Augustine grass shade tolerant?

Yes, some types of St. Augustine grass are shade-tolerant. There are over ten cultivated varieties of St. Augustine grass, and some are more tolerant to shade than others. If you live in a shaded area, be sure to choose a variety that will be able to survive without much sunlight.

Why is my St. Augustine grass turning yellow?

Often, St. Augustine grass that has turned yellow has been watered too much. Since rain leaches nitrogen from the soil, the grass is then deficient in nitrogen, and this can lead to yellowing.

Why is crabgrass so hard to kill?

Crabgrass is difficult to kill because it releases so many seeds during its short lifespan. One crabgrass plant can release 150,000 seeds. These seeds can then sit in the soil for up to 30 years before they begin to sprout.

This is why it’s best to be proactive and prevent crabgrass in the first place. It’s much more difficult to get rid of it once it has already taken root.