Can You Mulch Around Tomato Plants? (8 Mulches You Can Use)


Mulch is great because it suppresses weeds and retains moisture in soil.  However, if you aren’t careful, you can hurt your tomato plants with mulch.

So, can you mulch around tomato plants?  You can mulch around tomato plants – as long as the mulch does not touch the stems of your plants. Mulching around tomato plants insulates against temperature changes, prevents weeds from growing, and retains moisture in the soil. A layer of mulch 2 to 3 inches deep will be enough for tomato plants.

Of course, you will need to choose the proper mulch for your tomatoes, and you will need to apply it at the right time for the best results.

In this article, we’ll take a closer look at mulching around tomato plants, what you should use for mulch, how much you should use, and when you should use it.

Let’s get started.

Can You Mulch Around Tomato Plants?

You can mulch around tomato plants to provide protection from weeds, drought, and temperature changes.  However, you do need to be careful about what type of mulch you use, how much you use, and when you apply it.

mulch
When mulching around tomato plants, you need to choose the proper material, use the right amount, and apply it at the right time.

Before I talk you out of it, though, let’s take a look at the reasons why mulching around tomato plants is a good idea.

Why Mulch Around Tomatoes?

Mulching around your tomato plants has several important benefits that improve the health of plants and give them a better chance of survival. A layer of mulch around tomato plants can:

  • Suppress Weeds
  • Retain Soil Moisture
  • Insulate Against Temperature Changes
  • Reduce Fertilizer Leaching
  • Prevent Soil Compaction
  • Improve Soil Aeration
soil
A layer of mulch can retain moisture in the soil, which will make it easier to keep tomato plants alive during a dry spell.

As long as you don’t overdo it, a layer of mulch around tomato plants can have benefits that outweigh the risks.

Suppression Of Weeds

Mulching around your tomato plants will suppress weeds by preventing their seeds from growing (due to lack of sunlight).  As an added benefit, if you spread mulch over established weeds, it will smother them due to lack of sunlight and air.

weeds
Mulching can prevent the growth of weeds so that tomato plants do not need to compete with them.

With less competition from weeds, your tomato plants will have more water, nutrients, and sunlight. This means more energy to grow and produce lots of fruit for a good harvest.

You also won’t have so many seeds from weeds getting into the soil this year, which means less work pulling weeds next year.

Moisture Retention In Soil

Mulching around your tomato plants retains moisture in the soil. The layer of mulch traps water underneath, since the water will take longer to heat up and evaporate due to sun’s rays.

daylight
A layer of mulch slows down evaporation due to the sun, which keeps moisture in the soil for longer.

This reduces the need for frequent watering during hot, dry weather. It also reduces the chances that your tomato plants will dry out if you need to go away for a long weekend or a vacation.

When you water your garden, a layer of mulch will prevent soil from splashing up onto the leaves and fruit of your tomato plants.  This prevents the spread of soil-borne diseases that affect tomato plants.

Insulation Against Temperature Changes

Mulching around tomato plants helps to insulate the soil against temperature changes.  This helps to avoid cold damage to your tomato plants when nighttime brings chilly temperatures.

If cold temperatures threaten your tomato plants, check out my article on how to keep them warm.

tomato seedling
A thin layer of mulch around tomato plants will help to insulate the soil against chilly air on cold nights.

Mulching can also prevent the soil from heating up too much on a hot day.

Reduced Fertilizer Leaching

Mulching around tomato plants reduces fertilizer leaching.  This means that you can fertilize less frequently, and also worry less about polluting local water.

For more information on mulching, check out this article from the University of Georgia Extension on mulching vegetables.

The best part about mulch is that it will eventually decompose, providing nutrients to the soil (it also provides organic material if you use compost, leaves, or other natural mulches).

compost
Organic mulches will eventually biodegrade and turn into compost, adding nutrients to your garden soil.

Of course, the time it takes for mulch to decompose will depend on the material it is made from.

Prevent Soil Compaction

Another benefit of mulching is that it prevents soil compaction. Since tomato plants like loose soil, this will help to give your plants the ideal environment for growth.

According to the University of Massachusetts at Amherst, wood chips are an especially good mulch that resists compaction. They are biodegradable, so they will eventually add organic material and nutrients to the soil as well.

Improve Soil Aeration

When soil is less compacted, it will have better aeration. This means that tomato plant roots will not suffocate due to lack of air.

clay soil
Better soil aeration prevents wet soil, which can harm tomato plant roots.

Having a balance of air and water in the soil also prevents root rot (which can happen if the soil stays too wet for too long).

What Is The Best Mulch To Put Around Tomato Plants?

The best mulch to put around tomato plants may be something that you already have available in your yard (for free!)  Some good choices for mulching around tomato plants include:

  • Grass Clippings – these can come from your yard, a neighbor’s yard, or a landscaping company.  In addition to acting as mulch, grass clippings will provide lots of nitrogen to your garden when they decompose.  You can also turn grass clippings into compost before putting them in your garden.  For more information, check out my article on how to compost grass clippings.
  • Leaves – after a fall cleanup, there are lots of leaves around for the taking in your yard or nearby yards (just make sure to ask your neighbors first!) Again, landscaping companies may also have more than they know what to do with, so you could ask them as well.  Leaves can be used whole or chopped up (for example, by your lawnmower) before using them as mulch.
  • Sawdust – if you know someone who runs a sawmill, or a carpenter who does lots of projects, then you can get some sawdust for your garden.  One downside is that sawdust contains lots of carbon, so it can tie up nitrogen if mixed into the soil.  Use it on top of the soil as mulch, or else turn it into compost first before mixing it into the soil.  For more information, check out my article on how to compost sawdust.
  • Newspaper – if you can get old newspapers from neighbors, you can use them to cover the ground around your tomato plants.  This will help to prevent weeds just like any other mulch.
  • Cardboard – similar to newspaper, except that cardboard will take a little longer to decompose. However, it will still act as a fine mulch for your garden.  You can often find free cardboard boxes at Costco, BJ’s, and other wholesale clubs. To learn more, check out my article on uses of cardboard in the garden.
  • Wood Chips – this is what people often think of when they hear the word “mulch”.  Wood chips take a lot longer to decompose than grass or leaves, which is good if you don’t want to apply mulch so often.  Cedar and cypress resist decay, so they last the longest of all. They will eventually biodegrade to add nutrients and organic material to your garden.
  • Pine Needles – this is an option if you have pine trees on your property.  It is a good way to reuse the needles after you clean them up.
  • Compost – after composting yard waste and kitchen scraps, many gardeners mix compost into their garden soil.  This adds organic material to the soil, making clay soils drain better.  As an added benefit, it also adds important nutrients to the soil.  You can also spread compost on top of the soil to act like any other mulch by suppressing weeds, retaining moisture, and insulating against temperature changes.  For more information, check out my article on compost versus mulch.
cardboard boxes
You can flatten old cardboard boxes and put a layer of them over the soil around your tomato plants to make a good mulch.

Of course, there are a few things to avoid when choosing materials for mulching your tomato plants.

First of all, if you use wood chips as mulch, be sure to avoid painted wood chips. You never know if the paint is safe for gardening – if there is any doubt, avoid wood with paint.

If using grass clippings, make sure that the lawn they came from was not treated with pesticides or herbicides.  Otherwise, those chemicals can hurt your tomato plants or even end up in your food!

grass
Grass clippings are a good choice for mulch, as long as they come from a lawn that was not treated with pesticides or herbicides.

If you are using leaves, try letting them age for a while first (so they start to look more like compost than leaves).

You should avoid hay, since it often contain seeds from weeds that you do not want growing in your garden.

straw bale
Straw and hay can delay the warming of soil in the spring, which is not good for warm-weather crops like tomatoes. Consider using something else as mulch!

Also, hay and straw can slow the growth of warm season crops like tomatoes.  For more information, check out this article from the Michigan State University Extension on selecting mulches for your vegetable garden.

Is Wood Mulch Bad For Tomato Plants?

Wood mulch is not necessarily bad for tomato plants. It really depends on the size of the wood chips and the type of wood that was used to make the mulch (so pay attention to the source!)

For example, Black Walnut trees naturally contain a substance called juglone. Tomato plants are sensitive to this substance, so using Black Walnut mulch for tomato plants is not advisable.

black walnut tree
Black Walnut trees contain juglone, which can harm tomato plants.

If you mix very fine wood mulch into the soil, it will decompose quickly if there is high soil moisture or humidity in the air. At that point, the carbon in the decomposing wood can tie up nitrogen in the soil, preventing tomato plants from absorbing it.

To avoid this problem, avoid using sawdust or fine wood chips as mulch. Instead, use larger chunks, or avoid using wood chips in favor of other mulches (such as grass clippings, leaves, and cardboard).

How Much Mulch For Tomatoes?

According to the Texas A&M University Extension, a layer of mulch 2 to 3 inches (5.1 to 7.6 centimeters) thick will be sufficient for mulching around tomato plants.

If you do decide to use straw, a thicker layer may be necessary to prevent weeds from growing.  If you mulch multiple times during the growing season, consider how much you have already put down (and how fast the straw is decomposing).

compost bin
Spread a 2 to 3 inch thick layer of mulch around your tomato plants. You can use chopped leaves (shown here) as one option for mulch.

If you already have a thick layer of mulch, you may not need any more, or you may only need another inch due to settling.  Remember that too much mulch can kill your plants, so don’t overdo it!

For more information, check out my article on how too much mulch can kill plants.

When To Mulch Tomato Plants

You should mulch tomato plants in the spring after planting. If you put down mulch before planting, you are just making more work for yourself when you have to dig through an extra layer to make holes for your transplants.

Also, wait until the soil warms up to mulch around your tomato plants. Tomatoes need warm soil to grow – a soil temperature of about 70 degrees Fahrenheit (21.1 degrees Celsius) is ideal for growing tomato seedlings.

tomato plant 3-5-2021
Wait until after you transplant tomatoes outdoors to apply mulch over the soil.

If you apply mulch when the soil is still cool, it will delay the warming of the soil due to sun and heat (since insulation works both ways!)

For more information, check out this article on growing tomatoes from the University of New Hampshire Extension.

How To Mulch Around Tomato Plants

Once you have chosen a type of mulch to use, be sure that you get it from a clean source (for example, grass clippings from a lawn grown without pesticides or herbicides).

sawdust
Sawdust is one good option for mulching around tomato plants. Just make sure not to mix it into the soil, where it can tie up nitrogen and prevent plants from absorbing it.

Wait until the soil is warm enough for your tomato plants.  Remember to water before mulching if the soil is dry.

Spread a layer of mulch 2 to 3 inches thick around your tomato plants.  Spread it as far as necessary to prevent weeds from growing anywhere near your plants, since this will prevent competition for resources.

Avoid the temptation to put mulch around the base (stem) of your tomato plants.  Leave the soil bare right near the tomato plant itself to avoid stem rot.

At the end of the season, you can work grass clippings or leaves into the soil, where they should decompose over time.  Wood chips will take longer to decompose, so you may want to leave them on the surface or put them in a compost pile to let them decompose.

Conclusion

Now you know how to mulch around tomato plants safely – as long as you don’t use too much or get too close to the plants, you should be fine.  Be sure to choose the right mulch from a clean source and use the proper amount at the proper time.

You might also want to read my article on mulch vs. soil.

I hope you found this article helpful – if so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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