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The best time to plant grass seed depends on your local climate and whether you have cool-season or warm-season grass.

For cool-season grasses (like tall fescue), the ideal time to seed is late summer or early fall (typically August and September). During this period, the soil is still warm from the summer, but the air is cooler, creating optimal conditions for germination and root establishment before winter. There is also less competition from weeds. Spring is a secondary option, but cooler soil temperatures, the risk of a late frost, and less time for the grass to mature before summer heat can make it less successful.

For warm-season grasses (like St. Augustine), the best time to plant is from late spring through mid-summer (typically May and June), when temperatures are consistently between 75 and 90 degrees Fahrenheit.

In general, it is best to avoid seeding during winter or early spring, as cold soil and air can prevent seeds from germinating. For recommendations tailored to your specific grass type and climate, consider consulting a local lawn care professional.

Depending on the lawn treatments, the best times of the year to redo your lawn are between mid-August and mid-September for overseeding and renovation treatments. For areas such as the southern United States, lawn aeration works best during the fall, when the temperatures begin to drop. Otherwise, early spring is your next best bet because the grass is fresh and ready to absorb nutrients, and the temperature isn’t hot enough to fry the grass and the renovation materials.

Adding seed to existing grass is often known as overseeding, as opposed to reseeding. Reseeding refers to the process of filling in bare or dying patches of lawn—or in some cases, full lawns—whereas reseeding supports existing lawns to prevent thinning. Overseeding is an ideal annual lawn care practice for grass fighting drought, disease, weeds, or pest issues.

Although these terms sound similar and are sometimes used interchangeably, overseeding and reseeding your lawn are very different processes. Overseeding, the simpler of the two, involves a few steps to restore thinned or patchy grass by raking, aerating, and seeding uneven areas of turf to promote regrowth.

Reseeding a lawn is a more drastic and involved process, often necessary if the lawn is diseased, more than a third dead, or very overgrown with weeds. Unlike overseeding, it requires removing most of the existing lawn and starting a new one from scratch, a much bigger and more time-consuming job.