|By Skip Richter
Spring has sprung and our lawns are waking up from their winter rest. Some garden centers have already had lawn products on display for several weeks. Your competitive next-door neighbors may have already purchased turf fertilizer or perhaps a weed-and-feed product in their annual pursuit of the greenest, most perfect lawn on the block…as early as possible.
Lawns provide our landscapes with aesthetic beauty and the functional benefits of an outdoor carpet, while providing a cooling effect in summer and reducing erosion. However, in the effort to create the perfect lawn, many products are applied that are either unnecessary or ill-timed and are therefore ineffective.
So, grab the “Lawn Ranger” next door and let’s talk first about the what, when and how of spring lawn care, including scalping, dethatching, fertilizing, weed control, pest and disease management, watering and aerating.
Scalping is the practice of cutting the lawn as low as you can to remove the old, mostly dead top growth. Bermuda and zoysia lawns can regrow from rhizomes below the soil surface and therefore can be scalped lower than St. Augustine and centipede lawns that only have above-ground runners.
Scalping can result in an attractive lawn when the new growth fills in but has its disadvantages. It creates a lot of clipping waste that should be removed and utilized in composting or mulching elsewhere in the landscape and garden. It also opens the soil surface to sunlight, which increases the opportunity for weed seeds to get a foothold.
The bottom line is that scalping is an unnecessary practice for a well-managed lawn, and so I generally don’t recommend it. If you choose to scalp, do so at the end of winter prior to the emergence of new spring growth.
Thatch is a buildup of difficult-to-decompose, above-ground plant parts, such as stolons or runners. Clippings decompose rapidly and seldom contribute to thatch buildup. A well-managed home lawn in Texas generally will not have a thatch problem. If you promote excessive growth by overfertilizing and overwatering, especially with Bermuda and zoysia turf, thatch can become an issue. There is also some evidence that overuse of fungicides can play a part. If your Bermuda or zoysia turf has a thick layer of thatch, it is best to hire a professional with a vertical mower to remove it, while you sit and watch…and promise to stop overwatering and overfertilizing!
St. Augustine, Bermuda, zoysia, buffalo and centipede are slow to wake up from their winter rest. People often try to get them going faster with an early fertilization. However, when your St. Augustine lawn begins growth in the spring, it is primarily using nutrients stored in the plant. In time, it begins to send out new roots to replace the older ones that are dying off. Therefore, if you apply fertilizer in late winter to early spring, a significant portion of the nitrogen, which promotes growth and green color, can be lost to runoff from rainfall. Or the applied nitrogen can leach below the root zone before the grass has developed new roots to take it up.
While calendar dates can be a general guide for when to fertilize (such as mid-April in central parts of the state or early April in the southern third), not all spring seasons are the same every year. The best time to make your first fertilizer application is when you have mowed the turfgrass twice (mowing winter weeds doesn’t count). By that time, the grass is growing rapidly and has the new root system to take up the applied nutrients.
When you fertilize, apply about 1 pound of nitrogen per 1,000 square feet of lawn area. Divide the first number on the bag into 100 to get the pounds of fertilizer product to apply per 1,000 square feet. A mid-spring and/or late-summer application is generally adequate for home lawns. Recycling clippings back into the lawn also provides nutrients over time.
Choose a fertilizer based on a recent soil test. In the absence of a soil test, use a product with about a 3-1-2 or 4-1-2 ratio of nutrients. Examples of 3-1-2 fertilizer include 6-2-4, 15-5-10 and 21-0-0. Don’t get hung up on exact numbers. Just aim for the general ratio and use the advice above to determine how much you apply.
While these ratios are best guesses when you haven’t had a soil test, you may find that your lawn simply needs nitrogen, or perhaps nitrogen and a little potassium. Phosphorus tends to tie up in the soil and stick around a long time. In one northwest Austin neighborhood we tested, not one lawn needed phosphorus! So, it’s best to use soil-test results, rather than just buying something because it says “lawn fertilizer” on the label.
Herbicide applications are often ineffective because they are applied at the wrong time or misapplied, or an inappropriate product is used. As a result, weeds aren’t controlled, turf or other landscape plants can be damaged, and the chemicals can wash off into surface and/or underground water supplies.
The best weed control strategy is to build a dense turfgrass by proper mowing, watering and fertilizing. If the lawn is thin, weeds will become a problem. An old adage states, “Wherever the sunlight hits the soil, nature plants a weed.” If your lawn just has a few weeds, you may choose to do some hand pulling or to “mow and ignore” while you build turf density over time.
No herbicide controls all lawn weeds. It’s best to identify which type of weed you are dealing with so you can choose a product and application timing that will be effective. Weeds may be divided into: 1) annuals, biennials or perennials, 2) cool-season or warm-season plants, and 3) broadleafs, grasses or sedges.
Preemergence herbicides prevent weed seeds from sprouting — some can kill very tiny seedlings — while postemergence products kill existing weeds. Some are better against grassy weeds, others control sedges, while still others are more effective against broadleaf weeds.
If you are applying a preemergence product for warm-season weeds, you should make the first application in early to mid-February in the southern third of the state, and by early March in North Texas. Cool-season weeds sprout in the fall, so preventive applications should be made in early September, as a general guide. Follow the label carefully for application rates and note that a light irrigation should usually follow application to move the product down into the soil surface, where the seeds are waiting their debut!
Weed-and-feed combination products are popular but aren’t the best way to manage weeds. If they contain a preemergence herbicide, the problem is that in the spring, the time to weed is not the time to feed! So, do you apply it early to prevent warm-season weeds or do you apply it months later when the grass can best utilize the nutrients? Others contain herbicides that work on existing weeds, but may or may not have the best ingredient(s) for the weed species in your lawn. Some products that control existing broadleaf weeds can damage St. Augustine when temperatures are above the mid-80s.
Now all this may seem confusing, but the bottom line is to know what type of weeds you have, choose a product that will control them and apply it at the appropriate time. Your County Extension Office or a trained nursery professional can assist with weed identification and product selection.
There is generally no need for insecticide applications at this point in the season. Chinch bugs are a mid- to late-summer problem and grub treatments, if needed, aren’t applied until June or early July (from South to North Texas respectively).
The primary disease concern at this point in the season is take-all root rot. No treatments should be made unless the disease is diagnosed in your lawn and an appropriate product is prescribed.
As a general guide, lawns in full sun require about half an inch of water per week in spring and fall, and one inch per week in summer. Depending on where you live in Texas, rainfall can supply much of this water.
Overwatering and watering too frequently promote diseases and shallow rooting, which will come back to haunt you when things get really hot! When you water, wet the soil at least 6” deep by splitting the irrigation cycle into two or more applications spaced about an hour apart to prevent runoff.
Areas compacted from foot traffic will benefit from aerating. Most home lawns do not get enough foot traffic and compaction to need aeration. The aerators available in most rental companies “push” a solid tine into the soil, which compacts the soil around the aeration hole. It is better to use a hollow-tine aerator that removes a 1/2-inch core of soil and drops it on the surface.
You may need to hire a professional with such equipment, if aeration is needed. Aeration can help reduce compaction, promote root development and speed the decomposition of thatch. If you aerate, wait to apply preemergence herbicides until after you aerate because the process disturbs the soil surface.
These tips should get you on your way to a beautiful lawn, while protecting the environment and avoiding wasting your gardening dollars in the process.