Are Grass Clippings Good For Tomato Plants? [For Fertilization and Mulch]

Tomatoes can be finicky when it comes to first-time growers. Despite being pretty hardy, they continue to produce tomatoes even when the rest of the plant is diseased or otherwise afflicted. Mulch is generally beneficial, providing tomatoes with a trickle-down source of nutrients and minerals, but will grass clippings suffice?

Even though grass clippings hold little nutritional value for livestock, they are an effective mulch and fertilizer. They’re also cost-effective since you get them from doing nothing more than mowing your lawn. However, you do have to use them in a certain way. 

There are also a few things that you need to look out for when using grass clippings as a mulch for your tomato plants. As with everything else in life, it seems there are drawbacks to everything, and you might do more harm than good.

How to Use Your Grass Clippings as a Mulch

Fortunately, grass clippings are just about as cheap as they come. All you have to do is gather them up. Or, if you have a clippings bag attached to your mower, all of the gatherings are done for you. 

The problem is when to apply the grass clippings as mulch and how to do it correctly. It would be best if you waited until the clippings have dried and gone well past the point where they are done decomposing and going through their fermentation process. 

You don’t want to pile the stuff up around our tomatoes. Instead, just add several layers of the stuff around your tomato plants without stacking them against the plant’s stem. 

Give the tomato plant a little breathing room—about an inch all the way around.

Using dried grass clippings will give the mulch an advantage in longevity and will last a long time as they sit around the tomato plant. Even as they are emaciated and deprived of most minerals and nutrients, they still provide good shade and water retention.

You want your tomato plant to retain its easy access to water, even if the water pools from extensive rain, which is why you should give your tomato plants a little breathing room as you add your grass clippings mulch around them. 

Benefits of Using Grass Clippings as a Mulch

Most people look at grass clippings as a matter of trash—something that needs to be removed from the law as quickly as possible, so the lawn doesn’t look like a lumpy nightmare straight out of a Stranger Things episode. 

The truth is, that’s one of the advantages of using grass clippings as mulch. It gives you an excuse to gather all of the clippings up and actually have something to do with them, rather than tossing them in a leaf bag and heaping the bags in the dumpster. 

  • Grass clippings provide a shield/protection layer for the base of your tomato plants
  • They provide a substantial level of water retention
  • As the grass clippings decompose, they provide the tomato plant with vital nutrients and minerals
  • It’s an endless supply of free mulch material
  • If you have a large garden, you will have plenty of use for all of that grass
  • Provides some protective shading to the stem of the plant when the sun is at its most brutal
  • Grass clippings are an excellent combination material, especially for compost
  • Grass clippings prevent weeds from sprouting close to the tomato

So there are plenty of benefits when using grass clippings as mulch material around your tomato plants—and around any other plants, for that matter. 

Drawbacks of Using Grass Clippings as Mulch

As with all things, there are some caveats to using grass clippings around your tomato plants. Fortunately, some of those caveats are completely controllable by you, so you can minimize or completely eliminate the drawbacks.

There is a degree of timing before you place your grass clippings.

However you decide that you want to do it, you need to let them dry first. For example, if you use the bag on your mower to gather the leaves and grass, you will have to empty them out and allow them to dry. 

  • Grass clippings that are moist will create a matted, wet shield that deprives the tomato plant of oxygen, water, and sunlight.
  • Grass clippings are useful but not at their best, alone and unmixed.
  • If chemical herbicides or pesticides are present, they could cross from the grass clippings to the tomato, harming or killing it.
  • You must be concerned about cross-contamination if neighbors use herbicides or pesticides.

The above-listed reason is why you have to let the clippings dry. If that means dumping them out of your mower bag and letting them soak up the sun for a few days, then that’s what you have to do. You never want to put them in place as mulch when they are still wet.

If there is a chance that there might be lawn chemicals in the grass, you risk putting them around your tomato plants, even if you allow them to dry for a time before doing so. 

If your lawn buts up against a neighbor’s lawn and that neighbor used chemical treatments on their lawn, there is a strong possibility that you have at least a small degree of cross-contamination on your grass. 

When to Place Your Grass Clippings

Grass clippings contain roughly 5% nitrogen, so you don’t want to place them as mulch early before the first tomato fruits appear. A higher nitrogen level tells the plant to start developing more greens, as in leaves, rather than flowering and fruits. 

Since grass clippings can easily serve a dual purpose as both a mulch and a fertilizer, you can continue to sort of stack new grass clippings on top of the old as the old decompose into the ground. 

Since it takes time for the grass clippings to decompose enough to start releasing nitrogen into the surrounding soil as a fertilizer, you can place them with meticulous timing. As they decompose, the hope is that the fruit starts to show before the clippings get into the soil.

You’ll probably need a little experience to get the timing down right, so you shouldn’t start tossing grass clippings down as mulch until you know precisely when the tomatoes should start producing fruit. 

You don’t want the nitrogen hitting the soil until roughly 15 to 20 days after the first tomato fruits start cropping up. Also, you shouldn’t add more than one inch of grass clippings at a time. 

If you mix it in the soil as a fertilizer, you shouldn’t mix it so that there is more than one inch of the mixture in the soil. 

It’s all about timing when it comes to grass clippings, especially if you want to take advantage of the nitrogen. But, of course, if you don’t want to bother with letting the grass clippings release their nitrogen, you can always dilute your morning coffee and give that to the tomatoes when they need the extra nitrogen. 

Final Word

Grass clippings make for a decent mulch, providing several benefits to the tomato plant. So long as you are careful with how and when you place it and ensure that there are no chemicals involved, it should serve as a long-term, free mulch for the life of your tomatoes. 

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