A Question of the Week

lawn in need of renovation

Healthy lawns are able to withstand quite a bit of abuse. They can out-compete the majority of weeds and tolerate a fair amount of insect feeding, disease and drought without significant injury. Maintaining a healthy lawn is far from easy though. The drought in the summer of 2020 was particularly hard on lawns without irrigation, leading to decline and dieback on many properties. Here is what you need to know if your lawn is not meeting your aesthetic standards.

Which grass should you grow?

While there are hundreds of grass species, only those that are classified as cool season grasses are appropriate for New Hampshire lawns. Cool season grasses grow best in the spring and fall and grow slowly or go dormant during the heat of the summer. The top choices for lawns are Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescue. Each of these grasses has its strong points and shortcomings, and the scales will tip in their favor depending on the growing conditions of your lawn. Grasses are often combined in mixes to make the turf more tolerant of a variety of environmental situations.

Kentucky bluegrass is considered by many to be the best of the turf grasses for its deep green, fine-textured blades and dense, spreading growth habit. Kentucky bluegrass is the species lawn owners most prize when they want to be the envy of the neighborhood. Kentucky bluegrass is best suited to lawns with loamy soils, full sun exposure, and caretakers who are willing to commit to large amount of maintenance in form of fertilizing and watering. It does not hold up to drought as well as other species and requires irrigation during hot, dry spells to keep it from going completely dormant.

Perennial ryegrass is another favorite for New Hampshire lawns, with medium-textured blades and a spreading growth habit. It is usually mixed with other species because it has high wear tolerance and germinates rapidly. It will typically cover the soil and become established rapidly, while Kentucky bluegrass or fine fescues take a while longer to get going.

Tall fescue is a cool season grass that started off as a weed, and is still considered such by some. Tall fescue leaf blades are coarser than other species, and they have more of a bunching growth habit. However, the species is extremely tough and easily the most heat and drought tolerant of the cool season turf grasses. It also grows remarkably well in compacted soils, can stand up to a lot of foot traffic, and requires less nitrogen. Those in the southern part of the state looking to grow a more resilient and ecologically friendly lawn should keep tall fescue on their list.

Fine fescues have the finest textured leaf blades of any of the cool season grasses. They are the most shade tolerant too, and will hold up well to heat, cold and drought. Fine fescues do not need a lot of feeding and will grow just fine in well-drained, infertile, relatively acidic soils. They can be grown on their own or as part of a mix. Fine fescues germinate much faster than Kentucky bluegrass and can be used to cover the soil while the latter is becoming established.

Buying Seed

“You get what you pay for” applies when purchasing grass seed. Fortunately, grass seed packaging is required by law to list exactly what is contained within.  There may be one or more species with several varieties of each. For example, ‘Mystic’ and ‘Adelphi’ are two varieties of Kentucky bluegrass. You will also see purity listed, which is the percent by weight of each seed component, as well as the germination percentage and the date it was tested. Germination declines significantly as seed ages, so it is very important to purchase the freshest seed of the highest purity and germination rate possible. You’ll also want the lowest possible values of crop seed content, weed seed, noxious weeds, and inert matter.

When shopping for seed, you should also remember what the growing conditions are like in your yard (shade, drought, wet soils, etc.) and which grass species are most likely to thrive in those conditions. For example, a typical mix for an average sunny lawn might contain Kentucky bluegrass with lesser amounts of perennial ryegrass and fine fescue. For a shady spot, a good mix may include a majority of fine fescue or shade tolerant Kentucky bluegrass with a remainder of perennial ryegrass. For a sunny, drought-prone low-maintenance lawn, look for a fine fescue-heavy blend with smaller portions of perennial ryegrass and Kentucky blue grass. Those in the warmer southern parts of the state may also try a 100% tall fescue lawn.

When to Sow

Successfully sowing cool season grasses is all about soil temperature and climatic conditions. Cool season grasses tend to germinate best when the soil temperature is between 60 and 80°F and there is abundant rainfall. These conditions occur in the spring and fall in New Hampshire. However, fall seeding tends to produce better results. Grasses that are sown in the spring (late April through May) will have to face summer heat and drought before they are fully established. Young, short roots often aren’t up to the task without consistent and frequent irrigation. Additionally, competition with weeds in the spring and summer can be intense. Annual weed seeds tend to be most viable in the spring and are programmed to germinate towards the beginning of the growing season. Many annual weeds, such as crabgrass, thrive in hot weather.

Renovating and overseeding a lawn tends to work much better after the heat breaks in August and September. Weed seeds do not germinate as readily then, and grass seeds do well in cool fall weather. A young lawn should be able to survive the winter without issue as long as the plants are at least six to eight weeks old before the first hard frost.

Lawn Renovation Steps

  1. Regardless of whether you are starting a new lawn from scratch or renovating and repairing an old one, you will need to analyze the site and prepare the soil. If your is lawn is thin and patchy with weed issues, there is probably a limiting soil factor that needs to be corrected. Examples may include: poor or excessive drainage, soil compaction, acidic soil pH, or nutrient deficiencies. A good place to start is with a soil test, which will tell you the soil pH, availability of selected nutrients, organic matter content and lead level, and give you recommendations on how much lime and fertilizer to add.
  2. Controlling weeds in the lawn is essential. Most broadleaf weeds and crabgrass can be selectively controlled using a commonly available herbicide. However, it is not safe to reseed immediately after an herbicide has been used unless otherwise indicated by the product label.  Pre-emergent herbicides and “weed and feed” products should not be used prior to seeding because they can suppress or kill grass seedlings too. Always read and follow label instructions when using herbicides, making sure the product is labelled for the weeds you need to control and observing how long you need to wait before seeding.
  3. The next step is to correct the limiting factors that are inhibiting grass growth. This could mean grading the lawn area to reduce the slope or fill in low areas, aerating the soil, adjusting the pH, or reducing the amount of shade on the lawn. Many lawns in New Hampshire have excessively well-drained soils and would benefit from the incorporation of a two inch layer of compost or a three inch layer of rich top soil. If you are renovating an old lawn, you may need to remove the existing turf or till it under in order to incorporate compost, lime and other amendments. After tilling, rake the area to be seeded until it is smooth, and remove rocks or vegetative matter. It can be helpful to finish by rolling the soil with a lawn roller to provide a firmer base on which to work and sow seeds.
  4. If you don’t need to start from scratch, mow the lawn as low as possible and rake away debris. If an excessive thatch layer has developed (greater than a third of an inch), remove it with a dethatcher or dethatching rake. Grass seed needs to have direct contact with the soil in order to germinate and grow properly. Using a rake or dethatcher will loosen the upper quarter inch of soil and prepare it for planting.
  5. Fertilize and lime as indicated by the results of a soil test. If you do not have soil test results, put down approximately one pound per 1000 square feet of nitrogen, phosphorus and potassium each. Be aware that the majority of soils in New Hampshire are already high in phosphorus, so adding this nutrient may be unnecessary and polluting.
  6. Seed the area uniformly by applying seed in two directions perpendicular to each other. Depending on the size of the lawn area, you can spread the seed with a seeder or by hand. The ideal seeding rate will vary based on the species or mix you are sowing, though the majority will fall in the range of three to six pounds per 1000 square feet. Enough seed should be applied that there are 15 to 25 seeds per square inch of soil.
  7. Rake the area lightly to cover the seed with soil. Pressing the seed into the soil is also helpful by going over it with a lawn roller or lightly tamping it down with the back of a rake. Finish by mulching the area lightly with a layer of weed-free straw to conserve soil moisture and prevent rain or irrigation from washing away the seed.

Post-planting care

A newly seeded lawn area needs to be watered lightly and frequently. Ideally, the seed bed should be kept consistently moist from germination to establishment, which may require running a sprinkler over the area two to three times a day. How long it takes for grasses to become established depends on the species, but you should assume that it will likely take at least three to four weeks. After this time, you can cut the watering frequency significantly, but water deeper, to a depth of four to six inches. By the time the lawn is established, you should only be watering a couple times a week. Perennial ryegrass is the fastest to establish, and Kentucky bluegrass is the slowest. If you only partially renovated an old lawn or overseeded the entire area, continue to mow the existing grass while the new grass is becoming established. A new lawn area is ready for mowing once it is about three inches tall. Cut with a sharp mower blade to avoid stressing grass, and remove no more than one-third of the blades at one time.

Do you love learning about stuff like this? 


A monthly newsletter for New Hampshire gardeners, homesteaders and plant-lovers of all kinds, that includes seasonal suggested gardening tips, upcoming events and articles with proven solutions for your garden and landscape.

Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.