Practical Lawn Establishment and Renovation

Continued From Last Week

Rototilling

Assuming your existing soil is acceptable for planting your new lawn, the first step normally is rototilling (Figure 1). Rototilling serves two basic functions. First, it loosens the soil to a depth of 6 to 8 inches. Second, it breaks up the soil into smaller pieces so it can be graded.

With those two purposes in mind, it is clear that you need to go over the site only enough times to achieve the depth you want and a clod size you can grade. A common mistake is to pulverize the soil until it looks like powder. This destroys soil structure and ultimately leaves reduced infiltration and increased compaction potential. To avoid this problem, till soil when it is relatively dry, but moist enough that you don’t generate a giant dust cloud. Also avoid tilling wet soil, as doing so creates structureless soil and large, amorphous clods.

If you add compost, till the area once or twice and then add the compost and spread it to a uniform depth. Till the entire area again until a uniform mix is achieved. If you fail to get a good mix, the lawn will have pockets of soil and organic matter along with uniformly mixed soil. This will leave the lawn with wet spots and dry spots, meaning more headaches for you down the road.

If you determine that lime is needed to raise the soil pH, apply it before you till the soil and then till it in thoroughly to achieve a good mix. Remember that lime must react in the soil before it has any impact on soil pH. Applying it after the site is graded and compacted means it will affect only the surface soil and might take a long time to do anything to the rest of the root zone.

Grading

Once the soil is tilled, start grading by alternating raking and rolling. Large, lightweight grading rakes, which work better than small garden rakes, can be rented, as can water-filled rollers. Begin with a quick, rough grading aimed at knocking off high spots and filling in low spots. Then start rolling by going over the entire area with a back-and-forth pattern in one direction. As soon as you finish one direction, begin again in another direction. Meanwhile, use the rakes to continue to scratch off high spots and fill low spots.

Do a thorough job around the edges of sidewalks and driveways. It’s a good idea to grade these edges flush with the concrete since they will settle slightly once the area is irrigated regularly.

How do you know when the job is done? Fatigue alters most people’s sense of perception, so when they are really tired the lawn grade looks almost perfect. The goal is to grade the site smooth and have the entire area uniformly compacted so further settling does not occur during establishment. At the same time, you don’t want to pack the soil so hard that roots and water can’t penetrate. Unfortunately, this process can’t be quantified easily, so even if it is your first time, you will have to use your best judgment.

If you need to bring in additional soil, till and rough-grade the existing soil first. Then spread the new soil and follow with the rake-and-roll routine described above. This strategy works whether the new soil is the same as the original soil or is a sandy soil placed over the parent soil.

Selecting the best grass to plant

There are several basic mixtures that are adequate for most situations. The following examples will give you a reasonable chance of success. The percentages of mixture components are not sacred. Be flexible when shopping because every supplier’s mixture is different. Look for mixtures that approximate those described below. Lists of specific cultivars are included at the end of this publication.

You often can find reasonably good seed mixtures at discount chain stores. Most of these stores sell an elite mixture, an allpurpose mixture, one for shady lawns, and an economy mixture. Most likely, the economy mix is made up predominantly of annual ryegrass, which will die out within a year or two. The all-purpose mixture and shady mix often are pretty good. The elite mixture seldom is better than the all-purpose mix. The key is to study the label and make a decision based on contents, not the price or the hype.

Some independent nurseries stock improved grass mixtures. These are easy to spot because all of the grasses are listed by name, and the purity generally is high. Unfortunately, not all nurseries sell top-quality grasses. Become familiar enough with improved grasses to know what you are getting.

Fertilizing

Apply fertilizer just before or after seeding. If you have two spreaders, one person can put down seed while the other applies fertilizer.

For sodded lawns, incorporate fertilizer into the seedbed prior to final grading or, if planting on fertile soils, wait to apply it after the sod has put down roots. Sod often is prefertilized, so it might grow well for several weeks without preplant fertilizer.

For seeded lawns, you can use nearly any fertilizer that is relatively high in nitrogen (N). Twenty years of class planting projects have repeatedly yielded three consistent responses to fertilizer:

* Fertilizer has no observable effect on initial emergence of the grass seed.

* Nitrogen, either alone or in combination with phosphorus or potassium, stimulates growth after emergence and speeds establishment of the turf.

* Starter fertilizers high in phosphorus offer no advantage over regular turf-grade fertilizers high in nitrogen. Most books emphasize phosphorus and downplay the value of nitrogen. The key to rapid establishment lies in pushing growth after the grass germinates, which is best accomplished with nitrogen.

In most situations for seeded lawns, try the following approach. Apply a complete fertilizer (N-P-K) when you plant at a rate of 1.5 to 2 lb nitrogen per 1,000 sq ft. You can use 15-15-15 if you like, but regular turf-grade fertilizers high in nitrogen and potassium and low in phosphorus (e.g., 10-2-6, 21-7-14, 24-4-12, etc.) are best. Reapply at the same rate about 4 to 6 weeks after planting to further accelerate establishment. These will be the two most important applications you will ever make to your lawn.

Sodded lawns should be fertilized 4 to 6 weeks after planting or as soon as color and growth begin to decline.

Mulching

The next step in planting a lawn usually is mulching. Mulch helps keep moisture near the seed during germination. Applied properly and under the proper conditions, mulch speeds germination and improves stand uniformity (Figure 10). It is particularly useful on areas exposed to wind and prone to rapid drying. It also is useful in preventing surface erosion. It can even prevent earthworms from moving seed around in the course of their nightly wanderings.

One key when using mulch is to apply it fairly lightly (Figure 11). Make one, or at most two, passes with a mulch roller (Figure 12). You don’t need to bury the seed under 1 ⁄2 inch of mulch; an 1 ⁄8 to 1 ⁄4 inch of mulch generally is perfect. If you apply mulch too deeply, the seed might not be able to emerge through it.

The type of mulch is relatively unimportant, although finer mulches often work better than coarser ones. Fresh sawdust, aged sawdust, fine fir bark mulch, compost, ground-up grass straw, and peat moss can work well.

People often worry that mulches might tie up nitrogen in the soil, but when applied lightly this is not a problem.

Some dark-colored mulches greatly enhance emergence in late fall. This effect might be due to the fact that the dark mulch absorbs sunlight and raises the soil temperature.

Mulch isn’t always desirable. In late spring, summer, and early fall, mulch can cause surface heating and result in dampingoff diseases or what seems to be heat scorch. In some experiments, mulched summer plantings were lost, while unmulched plantings nearby came up just fine. Summer plantings are tricky because it is hard to keep them consistently moist without mulch, but mulch may lead to disease or heat scorch that can kill seedlings. You can see why it is worth waiting to plant during optimum times.

Mulch has an impact for only a short period of time. While big differences often are observed 2 to 3 weeks after planting, 6 months later it is difficult to tell which areas were mulched and which weren’t. In fact, seed applied to a wellprepared seedbed and then lightly raked in to ensure good seed–soil contact often does just as well as seed spread on the surface and then covered with mulch.

Considering the extra work and cost involved with obtaining and applying mulch, it might not be as important as we often think. The real issue isn’t the intrinsic value of mulch but rather keeping the seedbed moist enough for rapid and uniform germination. Good seedbed preparation, followed by light raking and careful irrigation, will accomplish this goal. Since careful irrigation is not always possible, most people find that mulch is a simple insurance policy.

Irrigation

The objective when irrigating a newly seeded lawn is to keep the seed wet so it can imbibe water and begin the germination process. You can’t do this by giving the area one thorough soaking. The best way is to irrigate two to four times each day for as long as it takes the surface soil to start to glisten. On heavy-textured soils, this might mean 5 to 15 minutes per irrigation. Generally, it takes longer the first day. By day 2 or 3, the soil glistens shortly after you start to water. If you keep the soil moist but not water logged, most grasses will germinate in 5 to 10 days at optimal temperatures.

During the germination period (about a week), you need to make sure the site gets water at the right time and in the right amount. Normally, you can’t depend on rain, so be prepared to do some babysitting. Also keep in mind that although the seedbed needs constant moisture, it makes no sense to drown the area. If the site puddles during irrigation and stays that way for more than a few minutes, you are watering too much.

After the grass germinates and green shoots are visible over most of the area, reduce the number of irrigations per day (for example from 4 to 2) and by the end of the second week to once per day. In the third week, you should be able to irrigate once every second or third day depending on the weather. By the fourth week, you often can reduce irrigation to 1 to 2 times per week. From then on, let the lawn tell you when it needs water, and irrigate accordingly.

Sod should be watered thoroughly just after planting and then at least daily for the first couple of weeks. Avoid overirrigating by randomly lifting sod corners to observe soil moisture and rooting progress. Remember to check a different piece each time you look.

Mowing

Mow the new turf as soon as there is enough grass to cut (Figure 14). Often, if the weather is good and you have done everything properly, the lawn will need mowing about 3 weeks after planting. Mow at the height you intend to maintain the lawn. For perennial ryegrass–fine fescue lawns, mow at about 2 inches. To prevent rutting, stop irrigation a day or two before mowing Rto let the soil surface firm up. Remember, you didn’t do all that grading just so you could ruin the surface by mowing when the soil is too wet!

Aftercare

Now the lawn is up, it has been mowed once, and it soon will be ready for regular weekly mowing. At this point, many people wonder why their new lawn is turning yellow. Remember, it is time to fertilize again. Young lawns are hungry and might need fertilizer every 4 to 5 weeks the first fall and following summer. By the time they are a year old, most lawns hold color longer after each fertilizer application and begin to require less intensive fertilization.

Renovating old lawns

Renovation refers to improving existing lawns by overseeding. Optimal timing for renovation is the same as for starting a new lawn.

Renovation often involves killing the existing lawn, dethatching, minor surface grading, and reseeding. In general, renovation does not involve rototilling, so it is less disruptive and more convenient in existing landscapes. What you do will depend on the condition of your lawn and your goals for the renovated lawn. Here are three common situations where homeowners often consider renovation.