Using Red Mulch to Grow More Tomatoes

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Are lots of ripe tomatoes not a sure thing where you live? Do you have trouble with tomato pests? Read on, because there may be a simple cure!

Red Mulch for More Tomatoes

I live in a place where cool season crops (like cabbage, broccoli, and cauliflower) grow fantastically, but where warm season crops (like corn and tomatoes) don't necessarily thrive. When we first moved to this homestead nearly eight years ago, I grew all our tomatoes in a small greenhouse. They did well, but I really wanted to see if I could successfully grow tomatoes outside, freeing up the greenhouse for other things. Last year, I finally got a good-sized garden in place and my hubby surrounded it with proper deer fencing. The tomatoes I planted did well...but many of them had to be ripened indoors. (Learn how to ripen green tomatoes here.) This year, however, I'm implementing some simple, but effective help.

Ripening green tomatoes indoors at the end of the growing season.

Increasing Chances of Ripe Tomatoes

For years I've known that there are two big things gardeners can do to increase the chance of getting ripe-on-the-vine tomatoes. One is to use a product called "wall o' water" or a plant cozy. This is a plastic tube that you fill with water and then wrap around each tomato plant. It increases warmth around tomatoes - because it's warmth, not light, that causes the fruit to ripen. While these devices work well, I grow so many tomato plants that I'd have to invest more money than I'd like to warm my entire crop.

Vine-ripened tomatoes are what we're after!

However, if you take a peek at those devices, you'll notice they are almost always red in color. Which leads me to the second thing gardeners can do to urge plants to grow ripe tomatoes: Use red mulch.

This may sound like a dubious old wives' tale, but Clemson University and the USDA's Agricultural Research Service did testing and development on red plastic mulch for tomatoes and discovered that this simple product can not only increase the size of individual fruit, but also increase overall tomato yields by 12 to 20%. (However, if you have ideal tomato growing conditions, red mulch may make absolutely zero difference in your crop yields; there are other benefits to using red plastic mulch, though...Keep reading.)

Now, mulch of any kind is beneficial in the garden. It helps suppress weeds and keeps moisture and warmth in the soil. But it is red plastic in particular that is magical for tomatoes. This is because certain pigments in tomato plants, called phytochromes, are actually color-sensitive proteins that regulate plant growth and development. These phytochromes have varied reactions to different types of light, and when light wavelengths from particular shades of red bounce up to tomato plants, the phytochromes make the plants fruit more abundantly and quickly.

Deterring Tomato Pests

But wait! There's more! It turns out red plastic mulch also deters root knot nematodes - pests that feed on the roots of tomato plants. The Agricultural Research Service believes this is because the light reflection from red plastic makes more of the growth of the plant happen above ground. In other words, more of the plant's energy and nutrition goes into making fruit and leaves instead of into making deeper, more nutritious roots...And without lots of nutritious roots to eat, nematodes are far less likely to attack tomato plants.

Using red mulch can increase tomato harvests by up to 20%.

How to Apply Red Plastic Mulch to Tomatoes

You can find red plastic mulch in many places where garden supplies are sold. Because I live in a small community, I ended up purchasing mine off Amazon. Here's the exact stuff I'm using; I chose this particular plastic because it's a bit thicker (3 mil.) than many other brands, and I felt this would be easier to work with, would keep the soil warmer, and might be reusable for a few years. 

I was tempted by the red plastic mulch sold by Gardener's Supply because it's perforated, which would allow rain water in. However, this was the only place I could find perforated red mulch, and it was fairly pricey once I added in shipping. Plus, if perforations allow more water in, they also allow more light in, and that could lead to more weeds - which would be more difficult to pull if they are under plastic.

First, I laid the plastic over my beds; to eliminate frustration while working alone, I chose to cut smaller pieces of the plastic and lay them down individually. Then I determined exactly where I wanted to transplant my seedlings. Everywhere I wanted a plant to go, I cut into the plastic with scissors, making a plus-sign shape. I folded back the triangles this created and then planted my tomatoes in the resulting holes. Because it's windy here, I may end up cutting off these triangle flaps; we'll see if they inhibit the seedlings in any way. Another option is to use a mulch hole burner (sometimes called a horticultural hole punch) to create perfect holes to plant your seedlings in.

Cut a plus sign in the plastic.

Fold back the triangle flaps and plant a tomato seedling.

I think you could easily weigh down the plastic with mulch or soil (just make sure the red plastic is well exposed all around the tomato plants; landscape staples might be a good choice if you choose a thicker plastic. But we are in a very windy area, so I felt bricks (which I had on hand) would be the easiest solution to keeping the plastic in place.

To irrigate my tomato plants, I water by hand with a hose, focusing the spray inside each  hole in the mulch. Another good option is to install drip irrigation or a soaker hose underneath the plastic.

Is Red Mulch Good for Other Plants?

You might wonder if red plastic mulch works well for any other plants. Good question! I've found sources saying it is also helpful for peppers and eggplants (which makes sense, because tomatoes, peppers, and eggplant are all in the same nightshade family), as well as strawberries (studies show the red plastic not only increases yields, but also makes strawberries sweeter), beans, melons, and even more abundant turnip greens. As far as I can tell, not a lot of research has been done on other crops, but it could be fun to experiment and see what you think.

My garden in progress, with some of the tomato seedlings nestled into red plastic mulch.

BONUS: More Tips for Ensuring Ripe, Red Tomatoes

If you live in a cool climate or have a short growing season, there are a few other important things you can do to ensure you get a good crop of ripe tomatoes:

1. Choose the right variety. If you live where temperatures are not ideal for growing most tomatoes, choose varieties that were developed for cool climates, such as those in Russia and Alaska. If your growing season is short, or you really want to maximize the number of ripe tomatoes you get, select varieties that mature more quickly, too.

2. Winter sow your seeds. Not all tomato varieties will sprout when you winter sow them, but those that are ideal for cool climates should! Learn how to winter sow seeds here.

3. If you choose to start your seeds indoors, do so 6 - 8 weeks before you'll plant them outdoors. It's important to give your plants a proper head start.

4. Manure tends to warm the soil, so add it in the planting hole and consider using it as a top dressing underneath your red plastic mulch.

5. Every yard has micro-climates; put your tomato plants in the hottest spot you have.

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