Spring and late summer or early autumn are the best times to apply fertilizers for many types of grass, and two annual applications are healthiest for the lawn. Annual applications provide the soil with nutrients and help them to grow. Giving the grass nutrients in the spring offers the plants the food they need to start growing after their winter dormancy. Springtime is the time at which the grass will use the most nutrients. However, the type of grass also affects when it needs to be fertilized.
Grasses that grow well in the cooler parts of the year, including Bermuda and fescue grasses, require fertilizer twice a year. Cool-season grasses experience a second growth period towards the end of the growing season in late summer or early fall. An application of fertilizer during this type of the year helps provide these grasses with the nutrients they need to grow in the fall and remain healthy during their winter dormancy. A larger application of fertilizer in the fall is most beneficial.
Like cool-season grasses, warm-season grasses benefit from extra fertilizer added later in the growing season. Warm-season grasses include bluegrass and tropical ornamental grasses. A larger application of fertilizer in the spring is best for warm-season grasses, but a smaller application to keep the grass healthy throughout the late summer and early fall is beneficial for these types of grasses, according to All About Lawns. Adding fertilizer at the end of the summer growth period keeps warm-season grasses healthy.
Applying fertilizer twice has the potential to cause fertilizer burn if it is misapplied. Dry growth seasons or seasons that produce little new grass growth allow fertilizer chemicals to remain on the surface of the grass, and adding more chemicals dehydrates the grass further, causing it to take on a burnt appearance. Only apply a second round of fertilizer if the ground is moist and the grass will not be damaged by it.