When to Plant Grass Seed in Iowa

Knowing when to plant grass seed plays a key role in how well your seed grows. There are certain times of the year when seeds do well. Panting seeds at the wrong time severely limits success. The best time to plant seed in Iowa depends on a range of factors, including the type of grass seed you choose and the expected weather conditions.

Fall is a fine time to plant grass seed in Iowa. According to the Iowa State University Extension, fall is preferable to spring because spring weather often is a time when lawns are infested with annual weeds. These weeds compete for dominance with new seedlings. Fall weather also features warm soil that is perfect for seed germination and growth.

According to Dave Minner, a turfgrass specialist at Iowa State University, fall planting ensures lawns are healthy and ready to grow again when spring arrives. Minner says the best time to plant straight Kentucky bluegrass is from mid-August to mid-September. "If you are forced to seed after mid-September, use a mixture with 60 percent Kentucky bluegrass and 40 percent perennial ryegrass by weight," said Minner. The ryegrass germinates faster to provide better winter cover for your lawn. Minner cautions that planting grass too late in the fall can lead to problems. "Grass seeded after October 15 may not even germinate, let alone establish a plant that survives the winter," says Minner.

The website IowaGardener.com recommends planting grass seed in September. It suggests planting during the first half of the month for those who live in northern Iowa and planting during the second half of the month for those who live in southern Iowa. The site also considers early October as a time to plant grass seed in southern Iowa. More caution must be used as cooler weather prevails. Avoid planting when cold weather is likely or imminent. The website Seedland.com says grass often goes dormant once temperatures are below 50 degrees. It recommends planting before daytime highs start to dip below 55 degrees.

Spring is a popular and effective time for planting grass seed in Iowa. According to the Iowa Natural Heritage Foundation, the spring planting season usually begins in April and runs through the end of June. The ideal time to begin planting grass seed in the spring is when the ground temperature reaches 55 degrees. Because cold-weather snaps can occur through April, you might want to wait until May before planting. Planting too early in the spring might lead to damage to immature seedlings, which can be killed by freezes and frosts. The website IowaGardener.com also recommends planting grass seed in May and early June.

The website Seedland.com suggests spring planting of cool-weather grasses when daytime temperatures range from 60 to 75 degrees. It notes that cool-season grasses grow best when soil temperature is between 50 and 65 degrees. Waiting too long can lead to trouble for grass, which often goes dormant during periods of extremely warm weather. Most cool-season growth stops when temperatures rise above 90 degrees. Planting seed too near the start of summer often requires significant irrigation to maintain the moisture levels necessary for successful growth of grasses, says the website.

Check the forecast and be sure the weather will agree with your plans. Do not plant seed if unseasonable weather threatens to introduce frost or heavy rains, which can wash away seeds.

Also consider the conditions of your yard. Is there lots of shade? According to the Iowa State University Extension, shaded areas require shade-tolerant fescue grass seed. They grow best when planted in April or from mid-August to early September.