播种建立庭院草坪

草坪是庭院景观非常重要的组成部分。一个生长、维护良好的草坪除可以提高房屋的价值；更具有减少泥泞、尘土、吸收噪音，控制土壤侵蚀，并产生氧气等作用。正确草坪建立和维护，对于草坪的健康状况和外观是至关重要的。草坪的建立包括草坪种类的选择、土壤的合理准备、播种和播后管理等方面。

草坪种类的选择

适合于草坪用的草有数十种，在北美常见的包括酥油草（Fescus）、结缕草(Zoysiagrass)、百慕大蓝草（Bermudagrass）、多年生黑麦草（Perennial ryegrass）、肯塔基草（Kentucky bluegrass）和匍匐剪股颖草（Creeping Bentgrass)六类。

1.酥油草（学名Festuca L.， 英文名fescus ）：酥油草常用的有"高酥油草" （Tall fescus） 和“细叶酥油草” (Fine-leaf fescus)”，原产欧洲，耐寒冷性强、种植区域广，耐贫瘠和酸性，在沙性和酸性土壤生长良好。优点是对维护需求低，缺点是不耐踏踩。

2．结缕草 (学名Zoysia japonica L.，英文名Zoysiagrass)：结缕草坚挺、稠密、针状叶稍、叶色浓绿，生长缓慢、耐踏踩，需求维护量少，适合高尔夫球场等踏踩多的地方。该草特别适宜种植于温暖区域、且在阳光充沛的地方生长良好。

3．百慕大草（学名Cynodon dactylon L.，英文名 Bermudagrass）：百慕大草的特点根系发达，耐盐碱、耐瘠薄，且耐高温和干旱，适应性强，在贫瘠的土壤上也能生长良好，所需要的修剪和维护较少。缺点是在温度低于10°C时开始休眠、甚至叶片变黄。

4．多年生黑麦草（学名Lolium perenne，英文名Perennial ryegrass）：原产于地中海一带，为寒带最佳草种，喜湿冷气候。多年生黑麦草坚韧、簇生、质地细腻、抗践踏，可用于足球场等运到场所以及学校、幼儿园等踏踩多的地方。

5．肯塔基蓝草（Poa pratensis L.，英文名Kentucky bluegrass）： 肯塔基蓝草叶色深绿，质地细腻，耐寒冷、抗干旱、生命力强、密度高。在干燥的条件下进入休眠状态，一旦获得水分可迅速恢复。是高尔夫等运动场所、公园和庭院广泛应用的草种。

6．野牛草（学名Bouteloua dactyloides (Nutt.) J.T.，英文名 buffalograss）：起源于从Montana 到Mexico 州的一种草坪草。其草质细腻，属于需水量少、少修剪少维护的草坪草。其抗旱和抗寒性非常强，从在Minnesota到Montana，再往南到Mexico州广泛种植。非常适合大的景观面积，如公园、商业区和学校等地。

7．匍匐剪股颖草(Agrostis L．,英文名Creeping Bentgrass)：匍匐剪股颖草是一种适合于冷凉地区的草种，草质细腻、颜色浓绿，但是生长缓慢。它的缺点是耐受荫凉能力差，需要比其他的草种较多的水分、肥料、修剪和管理。

根据草坪草对温度的敏感性，可分为冷凉型草坪草和温暖型草坪草。冷凉型草坪草包括肯塔基蓝草、多年生黑麦草、酥油草(包括高酥油草和细酥油草)、匍匐剪股颖草，这些草坪草特别适合北美的中西部地区。冷凉型草坪草在土壤温度10～18°C之间、空气温度在15～24°C之间时生长最好。在中西部地区这样的最适条件多发生在春秋两季。在没有灌溉的条件性，冷凉型草坪草在夏季高温季节进入休眠。冷凉型草坪草很容易用播种的方法来建立。

温暖型草坪草：常见的有结缕草、百慕大草、野牛草等，除主要用于较温暖的大部和南部州外，还用于冬季相对的中西部地区。结缕草、百慕大草抗寒性差、对低温敏感。温暖型草坪草在冷凉型草坪草在土壤温度21～32°C之间、空气温度在27～32°C之间时生长最好。这些草坪草在炎热的夏季生长旺盛。从中秋到第二年春季，因休眠而变为棕色。结缕草、百慕大草最好通过铺草皮的方法建立草坪；野牛草则可以通过播种的方法建立草坪。

在实际应用中，上面的这些草种子常混合起来使用，以适应多种气候和土壤环境。在商店中常见到的有各种品牌的混合草坪种子，主要分为适合光照充足区域的种子、适合荫凉区域的种子、适合半阴半阳区域种子、适合干旱和燥热区域种子、适合于践踏严重区域种子及肯塔基蓝草的混合种子等。

Establishment Methods and Timing

Determining the lawn establishment method is an important first step in the establishment process. In the Midwest, lawns are normally established by seeding or sodding; zoysiagrass plugging is also used occasionally.

There are both advantages and disadvantages to seeding a lawn. A common method of establishing a lawn is seeding, which involves planting grass seed on a prepared seedbed.

The advantages of seeding are:

the desired species or cultivars can be used;

the turf plants develop in the environment in which they must ultimately survive; and

establishment usually costs less than for sodding or plugging.

The disadvantages of seeding a lawn are:

the appropriate times for establishment are limited;

the turf is usually slow to develop into a quality stand;

reseeding areas with poor germination may be required;

quality seed may be difficult to obtain in some areas;

rain or irrigation may wash seeds off slopes;

weed encroachment is often a problem; and

a constantly moist seedbed is required during germination.

Sodding entails placing squares or strips of growing turfgrass and the adhering soil onto a final planting site. The strips or squares are tightly butted to one another to produce a complete cover of turfgrass. Kentucky bluegrass, creeping bentgrass, zoysiagrass, bermudagrass, buffalograss, and occasionally tall fescue can be established by sodding.

The advantages of sodding a lawn are:

an "instant" lawn is planted;

sodded lawns can be safely trafficked sooner than seeded lawns;

dust and mud are reduced;

erosion control is achieved;

sod can be planted any time during the growing season (provided the ground is not frozen and water is available); and

good sod is weed free.

The disadvantages of sodding a lawn are:

the cost is higher than for seeding;

choice of turfgrass species and cultivars used in sod production is limited;

sod is not produced in shaded environments;

a large volume of water is required during establishment;

incompatibilities between sod farm soils and soils at the planting site can cause sod to perform poorly;

sod may shrink, allowing weeds to invade between pieces; and

the speed of sod rooting changes with the season.

Although it appears there are fewer advantages than disadvantages to seeding a lawn, do not discount the importance of species/cultivar choices and development in their ultimate planting site. For example, obtaining perennial ryegrass or fine fescue sod will be difficult, perhaps impossible, in most areas of the region. If these species are desired in the lawn, seeding is the only way to establish them. In addition, soil incompatibility sometimes develops when sod is grown on soil that is different from that of the lawn area. Soil incompatibility can result in poorly rooted sod that has little tolerance to environmental or pest stresses. Thus, in many situations, the advantages of seeding may outweigh the advantages of sodding.

Plugging is sometimes used to establish zoysiagrass in the Midwest. Plugs are 2- to 4-inch diameter pieces of zoysiagrass with the adhering soil. They are planted 6 to 12 inches apart in a well-prepared planting bed and often take up to 3 years to fully establish and fill in completely.

Seed turfgrass lawns comprised of Kentucky bluegrass, perennial ryegrass, fine fescues, or tall fescue during spring or late summer and early fall . Late summer and early fall (August 15 to September 15 in central Illinois) is considered to be the best time. In the fall, weed competition is reduced, temperature s are appropriate for rapid growth and development, and grass seedlings have plenty of time to establish a good root system before the following summer's heat. Spring (April in central Illinois) establishment can also be successful. It is important, however, that adequate irrigation be available during summer's heat.

A cool season lawn can be sodded in central Illinois anytime during the growing season provided adequate irrigation water is available. Sodding or plugging a warm season lawn in central Illinois is best done in late spring to early summer (May 15 to July 1).

Soil Preparation

Proper preparation of the planting site can reduce many soil drainage and aeration, pH, and fertility problems that may not become evident until after the lawn is established. Correcting these problems after the turf is established is much more difficult than preventing their occurrence through proper site preparation, because the presence of the turf can limit your efforts. Thus, efforts to provide the best possible soil conditions are important to long-term success of a lawn.

The preparation steps (identical for seeding, sodding, or plugging) are:

1. Control weeds at the planting site.

2. Rough grade the site and remove debris.

3. Conduct soil tests.

4. Amend the soil as necessary.

5. Work and thoroughly mix the amendments into the soil to a depth of six inches.

6. Fine grade the site.

Eliminating weeds, especially perennial grassy weeds, will reduce competition with developing turfgrasses. Herbicides are valuable for eliminating weeds prior to lawn establishment. Consult the Cooperative Extension Service for a current list of recommended lawn care chemicals.

After eliminating weeds from the site, rough grade the area to facilitate surface drainage. Generally, a 1 to 2 percent slope (a drop of 1 or 2 feet for every 100 feet of run) away from buildings is adequate. Remove all debris brought to the surface by rough grading. Debris may include tree roots, stones, and leftover materials from construction.

If topsoil is needed at the planting site, incorporate it into the existing soil during rough grading. The final depth of topsoil should be at least 2 inches. Avoid using topsoil taken from sites that have recently been treated with agricultural herbicides; these herbicides could be detrimental to turfgrass establishment.

Soil testing provides a valuable means to determine if soils can support turf growth. For a small fee, commercial testing laboratories will evaluate soil pH, phosphorus, and potassium levels in a basic test. In addition, many other soil fertility and textural tests are available at an additional cost. Recommendations for corrective measures are also offered by many soil test laboratories.

Collect samples for testing during the growing season when soil temperatures are above 50·F. Samples should be 2 to 4 inches deep and the same size in diameter. Combine several (at least eight) samples collected from all similar areas in a clean bucket. For instance, in a yard having both high, dry areas and low, wet areas, two composite samples, one from each unique area, are required. Remove any plants or plant parts present in the sample and submit about a cup of each sample for analysis.

Soil reaction, a measure of acidity/alkalinity, is indicated by the pH results. The pH scale ranges from 0 to 14 with readings below 7 being acidic, above 7 being alkaline, and 7 being neutral. Based on the results of the pH test, amend soil to obtain a pH of 6 to 7 (slightly acidic). Slightly acidic soil reaction is desirable because it is at this pH that most soil nutrients are most available to growing plants. Add supplemental fertilizers as recommended by the soil test. It is easier to change soil before planting than after the grass is established.

Sulfur is used to make soil more acidic (that is. to lower pH). The amount to add depends on your soil type and the acidification desired. Consult the Cooperative Extension Service for help in calculating the sulfur required for your situation. Sulfur reacts slowly , so retest soil pH after 6 to 12 months to measure changes. Unfortunately, some soils resist acidification, making it virtually impossible to lower pH.

Ground agricultural limestone is used to make soil more basic (that is, to raise pH). Like sulfur, the amount to add depends on soil type and the desired change. Consult the Cooperative Extension Service for liming recommendations. To be effective, sulfur or limestone should be incorporated thoroughly into the soil by tilling. Avoid using slaked lime and burned lime because they are dangerous to handle.

Add phosphorus and potassium as recommended by your soil test. In the absence of a soil test, use 10 pounds of 10-10-10 fertilizer (or its equivalent) per 1,000 square feet to supply minimal fertility.

Amending heavy, clay soils or light, sandy soils with generous amounts of organic matter can improve the soil's drainage, aeration, and nutrient-holding capacity. If possible, apply a 2-inch layer of sphagnum peat moss, manure, compost, or some other quality organic material to your soil's surface. Use well-rotted organic matter to avoid problems with weed seeds, diseases, or other factors that can inhibit or detract from turf growth and development.

Work the amended soil to a depth of 6 to 8 inches using a rotary tiller. This operation will uniformly incorporate all amendments. After rotary tilling the soil particles should be marble sized or smaller.

Fine grade the site until it is smooth. Eliminate depressions that may collect moisture. Be sure that the slope away from buildings is 1 to 2 percent. Upon finishing this step, you are ready for seeding, sodding, or plugging your lawn.

Planting

Seeding

The seed label will provide valuable information about the grass seed. Information on the label includes the name(s) of the turfgrass species and cultivars present in the package, seed purity, seed germination percentage, crop seed content, amount of inert matter, weed seed content, lot number, and last testing date. In general, select high-quality seed of turfgrass cultivars recommended by the Cooperative Extension Service (see Turfgrass Selection). Record the seed lot number in case there are problems with the seed. This information will assist the vendor or producer to solve problems with seed should they arise.

Look for high and purity germination percentage (Table 1), fresh seed (produced the previous year), and low weed seed content (as low as possible ). Avoid buying unlabeled seed. The cost of good grass seed is a small price to pay for a high-quality lawn.

Table 1. Recommended minimum seed purity and germination percentages.

NOTE: Zoysiagrass and bermudagrass are commonly established by sodding or plugging, so they are not included in this table.

Providing enough seed to insure adequate coverage is important to seeding success, especially for grasses with a bunch growth habit (Table 2.). For lawn establishment using cool season species, provide a minimum of 10 to 20 seeds per square inch. Every seed will not produce a grass plant; a healthy, mature lawn usually averages six to eight turf plants per square inch.

Different turfgrasses have different seeding rates. These rates vary according to the size and weight of turfgrass seed. For instance, Kentucky bluegrass has a small seed and a high seed count per pound. On the other hand, perennial ryegrass has a large seed and a lower count per pound. Avoid excessive seeding rates that can produce crowded, weak, unthrifty plants and increase seedling disease invasion. In addition, excessive seeding wastes seed and money.

Table 2. Recommended turfgrass seeding rates.

After choosing the turfgrass and determining the seeding rate, be sure to distribute the seed uniformly over the planting area. Use a broadcast or drop spreader. It is advisable to apply half the seed in one direction, such as north to south, and then the other half in a different direction, such as east to west, to uniformly cover the entire area.

After the seed is in place, there are two activities that are crucial to successful turf establishment. The first is making sure there is a good seed-to-soil contact. Accomplish this task by using a lawn rake to lightly mix the seed into the upper 1/4 inch of soil.

Follow the raking with a light rolling to produce a firm seed bed. A light rolling can be accomplished by using an empty water-ballast roller. Rolling not only increases seed-to-soil contact, but firms the seedbed and slows drying of the soil.

Mulch with a thin layer of clean straw to prevent drying. Don't apply mulch heavily; you should be able to see soil beneath it. Usually 35 to 50 pounds per 1000 square feet (about 1 bale) is adequate. You do not have to remove the straw after the grass seed germinates. Grass seedlings will grow up through the light straw layer and gradually cover it as the straw decomposes. Raking off the straw would injure the young grass seedlings.

The second activity crucial to seed establishment success is to make sure adequate water is available throughout the germination process. At the time of planting, irrigate frequently and lightly, wetting the upper 1/2 inch of soil. Continue watering during the period of germination. Water less frequently, but more thoroughly and deeply, as grass seedlings mature.

Average germination times (Table 3.) vary according to the turfgrass species and the conditions under which germination takes place. Soil temperatures between 60· and 85·F for cool season grasses and 70· and 90·F for warm season grasses, along with a constantly moist seed bed, result in the quickest germination.

Table 3. Average germination time for various turfgrasses.