When to Plant Grass in New Hampshire

Grass grown from seed needs time to develop before it can withstand the harsh conditions of the warmest and coldest months. Planting grass within a few weeks of extreme cold weather or extreme heat can lead to failure. Maximize success by planting early enough to allow seeds to develop into healthy blades of grass but before hot or cold weather arrives. That means planting seed in fall or spring.

Grass seed needs four to eight weeks to develop. The length of development depends largely on the seed mixture you use. Target your planting to ensure that grass develops before unfavorable weather arrives and after it ceases for the year. In New Hampshire, that means planting in May and in August. By planting in these months, you minimize the chance that a cold snap in late spring or late fall will affect your grass before it has time to mature.

New grass needs lots of water to grow. By planting seed when rainfall is expected, you minimize the need for constant watering of your lawn, but you also want to avoid planting seed when heavy rainfall is expected. Too much rain can wash out seed before it is able to develop its roots in the soil. A second advantage of fall and spring planting is that rainfall is at its peak during these periods.

Remember to consider the impact of trees, which might be bare during fall and winter but could block sunlight during the warmer months.

Once you have chosen a seed, your most important decision will be whether to plant during the spring or fall. Roger Cook, a landscape contractor who answers reader questions for "This Old House Magazine," says he prefers fall planting in northern states.

"The soil is warm, but daytime temperatures are moderate, making watering less of a problem, and the weeds won't grow," he says. Cook recommends starting the seeding process in late August and continuing it until early October. "By the cool days of late October, the new grass should be fresh and thick and strong enough to survive the winter."

According to the website AllAboutLawns.com, the best time for fall planting is between August 15 and September 15. Because New Hampshire is considerably further north than, say, Virginia, the temperatures turn colder a little earlier. Thus, you probably want to start your planting before the calendar turns from August to September. The site also notes that you can spread seed in late fall, too. It simply will not grow until the spring thaw. Instead, it remains dormant through the winter. The downside, says the site, is that the seed can be washed or blown away in harsh weather, such as what occurs during New Hampshire's spring thaw.

Although some might recommend fall planting, the issue is less clear for someone who buys a house in December and hopes to have at least the start of a lush lawn by the summer. Who wants to wait until the fall? Fortunately, spring also works well for planting grass. The goal is to avoid planting seed that might be subject to harsh winter temperatures. A secondary concern is to plant seed earlier enough to allow the roots to develop before the summer heat arrives.

The most important factor is to wait until the snow has melted and the frost advisories cease. In New Hampshire, where spring arrives later than in other areas, wait until early May to plant seed. Follow the weather reports. If they talk of a possible cold snap in the first weeks of May, wait to plant the seed until the cold snap passes. Although it might push your grass growing into warmer months, the summer heat isn't as much of a factor as it would be in warmer climates.