Overseeding Starter vs. Fall Fertilizer

Overseeding starter fertilizer and fall fertilizer both have high percentages of phosphorus to promote healthy root growth. However, fall fertilizer contains a higher percentage of nitrogen. Understanding starter fertilizer and fall fertilizer will help you when determining how to fertilize your lawn. Applying a fall fertilizer at the time of planting may harm your newly planted yard, because a high percentage of nitrogen burns grass seedlings.

Overseeding Starter Fertilizer

Overseeding starter fertilizer is applied right before seeding. It is best to overseed your lawn immediately after applying the fertilizer to prevent weeds from taking advantage of the extra nutrients in the soil. Types of starter fertilizers include those with NPK amounts of 5-10-5, 10-20-10, 5-20-10 and 16-20-0, according to the University of California. Much like with your fall fertilizer, you must avoid spreading more than 1 pound of nitrogen in the soil at one time to prevent burning existing grass.

Fall Fertilizer

Unlike overseeding starter fertilizers, fall fertilizer is applied late in the growing season. Gardeners apply fall fertilizer in early fall, according to the University of Illinois. In addition, fall fertilizer is applied to established grass rather than to soil before seeding. Gardeners use a fall fertilizer that has a NPK amount like 13-25-12, according to Roger Cook from This Old House. This NPK amount helps roots continue to grow during the winter months for a quick green-up in the spring.

Fertilizer Application

Both overseeding and fall fertilizer are applied the same way. Divide the amount you intend to use in half. Pour half of the fertilizer into a rotary spreader. Push the rotary spreader slowly and vertically across the lawn. Add the rest of the fertilizer to the rotary spreader and apply horizontally across the lawn to achieve an even coverage. Water the lawn after applying the fertilizer. Allowing the fertilizer to sit on the lawn prevents the nutrients from sinking into the soil and raises the risk of fertilizer burn.

Other Factors

It is important to note when you overseed your lawn. New grass should not be fertilized for six to eight weeks after planting. Applying a fall fertilizer before the six to eight weeks are up can cause burnt grass. In addition, avoid planting your lawn too late in the growing season. Grass needs several weeks to establish before winter temperatures. Failure to sow your lawn at the right time results in dead grass due to winter injury.