How To Weed and Feed Your Southern Lawn

Growing, maintaining and applying a weed and feed to your southern lawn can be difficult. There are steps you can take to get a great looking southern lawn with Scotts Bonus S and Sta Green Southern weed and feed.

Lawns in Georgia, Florida, Texas and many southern states can have weed problems all year long.

Winter weeds grow in the fall and stick around until spring. Summer weeds start popping up in the spring and last until the fall. Pre-emergence herbicides work well to prevent weeds. When applied in the fall, they keep germination at bay and winter applications keep summer weeds down.

For homeowners who want a simple weed solution and one that also feeds their lawn, a weed-and-feed combination is needed.  Lowes stores have Scotts Bonus S and Sta Green Southern Weed and Feed to help you achieve a beautiful lawn this year.  Scotts Bonus S is recommended for use on St. Augustine grass, Floratam, centipede, zoysia and carpetgrass lawns

A weed free and green lawn is easier to maintain but you will need to put in some work to get there!  Lets get started by learning a little about the types of grasses.

Cool Season Grass and Warm Season Grass.

Most lawns in the south will have warm season grasses.  Warm season grasses thrive during the “warm season” of Spring and Summer when temperatures are between 80 and 95 degrees. Cool season grasses grow best in temperatures between 65 and 75 degrees and will struggle when temperatures get into the 90s.
Cool season grasses would be best suited for the climate in northern regions while warm weather grasses are better for the southern regions in the U.S.. Here’s a great article about the growing seasons of both grasses from Sports Turf Managers Association.
Cool season grasses start their growth early in spring and continue that growth with cool temperatures and rain.  When summer gets hot, these grasses typically go dormant, often “browning out.” Northern regions typically see a great Bluegrass lawn in May only to see it disappear by July, and come back in September.
Cool season grasses are best planted/seeded in early spring or late summer/early fall.  They tend to germinate and establish quickly.  Blade color looks best during late spring and early summer. This group of grasses includes Kentucky Bluegrass, Tall and Fine Fescues, and Ryegrass.
Warm-season grasses are originally from sub-tropical regions, which is why they thrive in the warmer temperatures of the south. These grasses are grown in Georgia, Florida, South Carolina, Louisiana, Texas, New Mexico, Arizona and Southern California.
The areas surrounding the Gulf are best suited for Zoysia, St. Augustine, bahiagrass and centipede grass while the arid parts of the south typically are best for Bermudagrass because of its excellent drought tolerance. Grasses in this group include Bermudagrass, Buffalograss, and Zoysia grass.
All of these grasses take longer to green up in the spring and tend to go dormant quicker in the autumn. However, they’re able to thrive in summer heat that would otherwise kill the cool-season grasses.
Warm-season grasses form a tough, dense turf that gets thicker as they get older. They typically grow fastest at temperatures between 80 to 95 degrees and often go dormant during the winter, turning tan or brown. Bahiagrass grows primarily along the Gulf Coast.
Some warm-season grasses are more cold-tolerant than others, which is why zoysiagrass, centipedegrass, and Bermudagrass are often grown in the Upper South, or in the transition zone.

Weed Life Cycles

Weeds can be divided into categories based on life cycles. With most weeds, a weed and feed herbicide must be applied at a specific time of year for effective control. Applying a herbicide too early or too late often leads to poor weed control.

Annual Weeds: Annual weeds complete their life cycle in less than one year and reproduce by seed. Annuals may be further divided into summer and winter annual weeds.

Summer Annuals: Summer annuals germinate in the spring months, live during the summer and mature in the fall months. Examples include crabgrass, goosegrass, lespedeza and prostrate knotweed.

Winter Annuals: Winter annuals have a life cycle opposite from summer annuals. Winter annuals germinate in the late summer and early fall months, live during the winter and die in the late spring or early summer with the onset of high air temperatures. Examples include annual bluegrass, common chickweed, henbit and swinecress.

Biennials: Biennial weeds live for two years. During the first year, biennials germinate from seed and produce vegetative growth. In the second year, biennials form a seed stalk, produce seed and die. Biennials are not as common in lawns as annual and perennial weeds. Examples include wild carrot and common mullein.

Perennials: Perennial weeds are usually more difficult to control than annual weeds because they reproduce by seed. Perennial weeds include crabgrass, nutsedge, goosegrass, spurge, dollarweed,  dandelion and wild garlic.

Southern Weed and Feed: What works and how to apply.

The two herbicides most commonly used in fertilizer and herbicide weed-and-feed formulas are the selective herbicides Trimec and Atrazine.

Trimec is a selective, contact, systemic herbicide that is a combination of three chemicals: 2, 4-D, dicambra and mecoprop, all of which are damaging to warm season grass. This chemical is commonly found in weed and feed products for cool season grasses.  Applied to a wet lawn, the granules of Trimec stick to the wet weeds and effectively kill them.

Atrazine, commonly used in weed and feed formulas for warm season grasses like St. Augustine, is a selective herbicide that kills systemically through interruption of photosynthesis.  The weeds absorb the atrazine through its roots.

That stops the weeds ability to absorb energy from the sun and they die.  Most atrazine based products need to be applied to a dry lawn. When weeds are present, spread the granular compound on dry grass and water in and make a maximum of two applications each year.

Note: Scotts Bonus S is recommended to be applied to a dry lawn.  Sta Green Southern weed and feed is recommended to be applied to a wet lawn.

For 2017, Sta Green does not use Atrazine in their Southern weed and feed. They started using Penoxsulam last year.

Always follow label instructions from the manufacturer, as application guidelines may change.

Depending upon the brand, atrazine is labeled for centipedegrass, zoysiagrass, St. Augustinegrass and dormant bermudagrass. Atrazine can be applied to actively growing and dormant centipedegrass or St. Augustinegrass. Bermudagrass can be injured if treated with atrazine while actively growing.

Atrazine should not be applied to tall fescue, Kentucky bluegrass or when warm-season grasses are emerging from winter dormancy. Atrazine has preemergence and postemergence activity on a wide variety of broadleaf weeds. Results on goosegrass and crabgrass is generally poor. DO NOT apply atrazine over the root zone of desirable trees, shrubs and flowers.

Atrazine is the active ingredient in Scotts Bonus S  and Sta Green Southern.

Fertilizer provides a simple and easy way  to distribute herbicides that must be applied to our lawns prior to weed seed germination if it is to be effective. However, there is a downside to using these weed and feed fertilizers in the spring for southern lawns.

These fertilizer products contain pre-emergegent herbicides formulated with somewhat high nitrogen content for cool season grasses.  When these fertilizers are put on dormant warm season turf, it will most likely feed existing winter weeds. And those weeds will compete for space when your lawn begins their spring growth.

With too early high nitrogen fertilization, you may also be setting your lawn up for cold injury from a late season freeze. Therefore, my suggestion is if you use a weed and feed fertilizer after using a  pre-emergent herbicide, try to find a fertilizer  that is low in nitrogen or one that the nitrogen source is in a slow release form.

Most southern lawns can wait until they have gone through spring and have been mowed at least twice before applying any spring nitrogen fertilization.

How to Apply Southern Weed and Feed

Southern weed and feed needs to be applied when grass is dry. Watering after application will help activate the product.

FERTILIZE – two to four times a year. Minimum 4 weeks between applications.
Late February-Early March – apply for an early green-up. Most companies that make slow-release fertilizers that provides for a quick two-week green. Some people will be tempted to use a weed-and-feed at this time, but don’t. However, spot weed-and-feed treatments are recommended for those with landscapes that have been established for many years.

Warning: Most weed-and-feeds contain Atrazine which burns roots of young trees and shrubs. Try a fertilizer product only like Scotts Green Max or Sta Green All Season. These are fertilizer only with no weed control.

Late March-Early May – apply slow-release weed and feed fertilizers. Scotts Bonus S or Sta Green Southern.

October-November – Apply winterizer formulas for winter hardiness. Ratios vary, but make sure they are “winter” or “fall” formulas designed for southern grasses.

June-September – if grass looks yellow, use an application of either granular or liquid iron. Once a year should be enough. Try Scotts Southern Turfbuilder with Iron.

Read and follow labels and warnings before using weed-and-feed products on St. Augustine turf. Avoid the dripline of trees and shrubs to prevent damage. Ingestion of atrazine or contact with skin or eyes can be harmful. Wear protective eyewear, long sleeves and pants, gloves and dust masks while working with weed-and-feed products containing atrazine.

Wash off the spreader and any other equipment used during the application.  Generally, you need to feed warm-season grasses from late spring to early fall. If you feed too early in spring the nitrogen likely promotes rapid growth of cool-season weeds. If you fertilize too late in fall, the grass is likely to be less hardy as it enters cold weather and more susceptible to winter injury.

Fall:When temperatures drop to 65-70 degrees at night, apply preemergence herbicides to control winter annual weeds such as annual bluegrass,  henbit and chickweed.

Spring: Apply herbicides to control summer annual weeds such as crabgrass and goosegrass prior to soil temperatures reaching 55° F. Postemergence herbicides are applied after annual weeds emerge or when new growth or regrowth of perennial weeds appears. Follow these guidelines for better weed control and improved turfgrass tolerance:

  1. Apply postemergence herbicides in the fall and late spring months. Many annual weeds are actively growing during these times of year and are easier to control with postemergence herbicides.
  2. Do not apply herbicides to grasses that are stressed due to high temperatures or drought.  Also, weed control is poorer when herbicides are applied to weeds in a stressed condition.
  3. Do not apply postemergence weed and feed during the green-up transition from winter to spring growth phase of warm-season grasses. The risk of injury is greater during the green-up process than when the grass is fully dormant or actively growing.

Summary: For weeds, use a pre-emergent in the fall and spot weed killer if necessary. Then weed and feed fertilizer once the grass is completely out of dormancy. To help your lawn maintain its color during the hot summer months, water regularly and deeply if not restricted by local ordinances.

Bermudagrass and other southern grasses go dormant when the temperature drops.

Many homeowners overseed with ryegrass for the cooler months. This keeps the lawn nice and green instead of brown. The ryegrass dies off when the temperature climbs back up again, letting the bermudagrass grow in.  Repeat for the next year. Hopefully this plan will make your lawn the envy of the neighborhood.

By Victoria Stone

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