Plastic sheet mulches seem like magic. Not only can they suppress weeds and help retain moisture, but some boost production and deter pests. Let’s look at what’s out there and their best uses.

When using any of these mulches, the best way to install them is to set out your drip irrigation hoses, then spread out the plastic mulch, tacking down the ends to prevent it from blowing out of place. When it’s time to plant, cut the plastic mulch, dig a hole, and plant your transplant. 

Garden Mulch: A Rainbow of Options

White on Black Sheet Mulch

The white on black mulch keeps weeds at bay because the black plastic reduces the light that reaches the soil so not as many weed seeds germinate. Some studies indicate that it cools it up to 12 degrees F. It’s often used for cool season vegetables such as broccoli, cabbage, especially for spring and fall crops. Yet, the white side of the mulch reflects the sunlight providing more light for optimum growth, which is especially important during the beginning and end of the season. 

Black Sheet Mulch

Gardeners have used black mulch probably longer than any of the others because it is useful in suppressing weeds, reducing evaporation, and warming the soli. But after reading the previous entry on the white on black mulch, you might ask, “How can it warm the soil when with the white on black mulch, the black side keeps it cool?” The thing is, with the white on black mulch, the white reflects the sun, preventing the black from absorbing the heat. Using just black mulch is a terrific way to warm the soil, particularly early in the season, ultimately increasing yields. 

When it comes to the black sheet mulches, there are paper options besides the plastic ones for those who prefer not to use plastic. 

What Pest Deterrents Worked

Red Sheet Mulch

Decades ago, a company sent me red plastic sheet mulch to try on my tomatoes. It claimed that it increased production by 20 percent. I was dubious, but decided to put their claim to the test, planting one row of tomatoes with the red mulch and one without. At the end of the season, the one with the red mulch had a significant advantage on growth and harvest. I can’t say that I counted the tomatoes that I picked, but I think claiming a 20 percent increase is within an accurate level. 

From what I understand, the red mulch works because it reflects a specific red light wave back to the tomato, which triggers a color-reactive protein within the plant that promotes growth. It definitely works for me here in Montana, although I have read subsequent studies that report it does not have the same results in Southern parts of the country. 

The red mulch is also being used more with strawberries with reported success. I have not tried it with them, yet, but it might be worth a test row or bed. 

Silver Sheet Mulch

I recently learned about silver mulches when researching white flies, and am impressed with the benefits of using this metallic colored mulch. The shiny silver disorients insects such as whiteflies and aphids that not only harm the plant, but are vectors of disease. Silver mulch would be terrific to use with Brassicas that are prone to flea beetles, as well as squash, cucumbers, and melons that suffer from viral infections spread by pests. 

There are some metallic mulches that have a black stripe down the center. This is to boost the soil temperature around the young plants. My recommendation is to try it with and without the stripe to see what works the best in your garden. 

It’s remarkable how utilizing these simple sheet mulches can offer a significant improvement to the harvest, as well as reducing the work in the garden. Give them a try and let me know what you think!