Pre-emergent Herbicide For St. Augustine Grass

When it comes to weed control, most lawn owners find it more challenging, especially for the repetitive and stubborn weeds. If you have St. Augustine grass on your lawn, you might have realized that difficult-to-control weeds commonly plague this evergreen grass. That’s why you need to stay on top of weed control measures.

Naturally, St. Augustine grass requires water, sunlight, and adequate soil contact to survive. Weeds, too, require the same condition making it unquestionable to find many weeds in your lawn with St. Augustine grass.

When it comes to controlling weeds on your lawn, you want to apply herbicides on St Augustine grass as early as before the weeds emerge and go on until the grass forms a thick continuous layer that completely covers the soil leaving no space for weeds to grow.

This article will cover some of the pre-emergent herbicides you can use on your St. Augustine grass lawn and other aspects related to the topic.

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Pre-emergent herbicides to use on St. Augustine grass

St. Augustine lawns are coveted for their ability to thrive in a wide range of light and soil conditions. Unfortunately, they are not impervious, particularly against weeds. On the other hand, there are many pre-emergence herbicides that can help you control weeds on your lawn.

As the name suggests, pre-emergent herbicides prevent weeds before they emerge from the soil surface. Usually applied in spring as the temperatures start to warm up, pre-emergent herbicides kill seeds as they germinate. Here are some of the best and safe pre-emergent herbicides for use on your St. Augustine lawn:

Bensulide
Oryzalin
Isoxaben
Prodiamine
Dithiopyr
Pendimethalin
Benefin+oryzalin
Benefin+trifluralin

The best pre-emergent herbicide to apply depends on the weed species present, among other factors.

Oryzalin addresses many annual grass and broadleaf weeds. Bensulide is ideal for controlling crabgrass, goosegrass, and bluegrass. Prodiamine controls a vast range of weeds and even stays in soil longer. Dithiopyr keeps the roots of many types of grass and broadleaf weeds from growing. Isoxaben is an excellent option for homeowners battling broadleaf weeds, including spurge, oxalis, and knotweeds.

Applying pre-emergent herbicides on St. Augustine grass

Pre-emergent herbicides are usually applied on the grass to disorient the germination and growth of weeds but not by completely killing the seeds. By the time the seeds are ready again to germinate, the St. Augustine grass will be established and compact, so the weed will lack space to grow and thrive.

That said, timing is a very critical factor when planning to apply pre-emergent herbicides. The soil temperature at the time of applying herbicides is also a fundamental consideration to ensure the herbicides are effective.

The best time to apply pre-emergent herbicides is in the spring when the soils are warm. Depending on your geographical location, you can check the exact months when your soils are warm and free from the dangers of frost.

This is the time when you should apply pre-emergent herbicides on your lawn. The thumb rule is to apply pre-emergent herbicides when the soil is consistently above 55 degrees Fahrenheit. It is advisable to use a soil thermometer to easily determine the exact soil temperature.

The first spray will regulate the spring and summer weeds from germinating. You will need to spray the herbicides the second time in mid-fall to control the winter weeds.

What weeds do spring pre-emergents control?

When applied in spring, pre-emergent herbicides control a wide array of both grassy and broadleaf weeds. If there are some weeds that occur in your garden every year, the best way to control such weeds is by buying herbicides specifically designed for the weeds.

Basically, no single pre-emergent herbicide works for all the weeds on your lawn.

Some of the most common weeds that are controlled by pre-emergent spring herbicides are clovers, prostrate knotweed, spurge, goosegrass, chickweed, lespedeza, dandelion, and dollar weed.