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When to Fertilize New Grass?

If you have a new lawn or you want to repair damaged parts, you should grow new grass. Ideally, the seeds will become seedlings and grow large enough to be lush and healthy. However, there are cases when they don’t survive for long – and fertilizer application might be the problem.

Thus, it’s essential that you know when to fertilize new grass.

When To Fertilize New Grass?

Fertilize Early and Get the Right Mix

Ideally, you should be applying the fertilizer either before you sow the grass seeds or while doing so. Now, fertilizers will generally have the three essential elements for plant growth: nitrogen, phosphorus, and potassium. These are respectively referred to as N, P, and K on the fertilizer packages. Some fertilizers have an equal amount of N, P, and K. Other fertilizer mixes will have more nitrogen than the other two elements.

applying fertilizer

Source Amazon

When fertilizing new grass, do not use a package with high amounts of these elements. High levels of N, P, and K, are beneficial for the growth of existing grass, but new grass does not need as much. Thus, don’t pick any random fertilizer mix. Ensure that you get a quick-release starter fertilizer with just the right amount chemical element ratio.

Starter fertilizers for new grass aren’t made the exact same way, but they are likely to be a quick-release variant. In contrast to a slow-release fertilizer that is used often to prepare the lawn for the summer, a quick-release fertilizer immediately gives the grass seeds the nutrients they need. In particular, the new grass will have a good germination period and their roots will be established fast.

Here is a video of starter fertilizers:

Second Application of Fertilizer

After giving your new grass some quick-release starter fertilizer, it might still need more nutrients to grow. Not all lawn owners would need to a reapplication of fertilizer, but it’s not uncommon if you perform it again after three or four weeks. This is when the new grass has reached a height ranging from an inch to 1.5 inches.

By fertilizing again, you promote deep root growth while also preventing the proliferation of weeds. Remember to use a lawn fertilizer instead of a starter fertilizer this time. The amount should range between about half to a pound of nitrogen for every 1,000 square feet of lawn.

Quick Tip on Weed-and-Feed Products

You might be considering the use of a weed-and-feed product for your second fertilizer application. However, we do not recommend this due to their effects on the new grass. They usually have herbicides for treating broadleaf weeds or crabgrass affecting seed germination. The exception is the one that has Siduron, which is safe for use on grass seeds and seedlings.

Fertilizing Newly Laid Sod

Fertilizing Newly Laid Sod

We now know when to fertilize newly planted grass seeds, but what about newly laid sod? While it is indeed a fast way to improve the look of your lawn, it can immediately turn brown with inadequate irrigation and fertilizer application.

Unlike with grass seeds that need a quick-release starter fertilizer early on, you must first wait for one and a half months before you can apply any fertilizer. In fact, you can wait for up to two months to ensure that the roots of the sod have been firmly established in the soil.

For fertilizing sod, you should get a slow-release fertilizer. Using a quick-release variant would be too much. Also, avoid getting a fertilizer mix with a high amount of nitrogen for the first application. You can opt for a granular lawn fertilizer with an N-P-K ratio of 5-14-42 to support root establishment.

To have an efficient coverage, use a broadcast spreader. One pound should be used for every 1,000 square feet of lawn. Read the instructions on the label of the slow-release fertilizer package and irrigate the sod deeply after applying the fertilizer.

Second Fertilizer Application of Sod

Using Broadcast Spreader

Source: Amazon

Before you apply fertilizer on your sod again, do wait from six weeks to eight weeks. Also, the fertilizer you should be using by now must be a granular lawn fertilizer with a high amount of nitrogen. An example would be a 25-10-10 fertilizer. Use the broadcast spreader again, but the nitrogen to be used or now must be two pounds for every 10,000 square feet of lawn. Don’t forget to irrigate the sod afterward.


In conclusion, you must take note of the differences in fertilization application for new grass seeds and newly laid sod. The former requires a quick-release fertilizer immediately while the latter is better off with a slow-release variant several weeks after it has been laid on the lawn. Both of them, however, would benefit from a second application to support root establishment.

We hope that our guide helped you ensure that your new grass will grow well. If you have any questions, feel free to send us a comment.

About the Author Ann Katelyn

I'm Ann Katelyn, Creator and Chief Author of Sumo Gardener. Since I was a child I've always been fascinated with plants and gardens, and as an adult this has developed into my most loved hobby. I have dedicated most of my life to gardening and started Sumo Gardener as a way to express my knowledge about gardening with the hope of helping other people's gardens thrive.

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