I was listening to a podcast by one of my favorite market growers from Alabama, Noah Sanders, and he had a guest on from Kaleva, (Northern) Michigan, Craig Shaaf, from Golden Rule Farm who mentioned that he put red dye in an empty soda bottle and it helped his tomatoes mature earlier than anyone else’s tomatoes in the area while also sighting a Clemson University Study.
So, being that we drink a lot of sparkling water in our house, I had an empty liter lying around (we typically repurpose these for terrariums in cold hardy annuals but that’s a something to discuss for another day), so I filled it with some water and added several drops of red food coloring to it and sat it on my indoor Tower Garden near some micro dwarf unripened cherry tomatoes I was growing. Low and behold, two days later, the cherry tomatoes closest to the red-colored water began to ripen from the bottom up!
Red reflective Far-Red light encourages tomatoes to ripen.
Studies using Red Plastic Selective Reflecting Mulch (SRM) Show Increased Yields for Certain Plants
Research originally started during the 1980s and led to development of SRM-Red, a selective reflecting mulch that has been available commercially since 1996. Plant physiologist Michael J. Kasperbauer, who retired from the Agricultural Research Service‘s (ARS) Coastal Plains Soil, Water and Plant Research Center at Florence, S.C. found that plastic colored-mulch’s controlling factor is not the colors themselves, but how the colors adjust the amount of blue light and the ratio of far-red (FR) to red light that plants receive reflecting from the ground upwards.
The studies used a red plastic mulch (also referred to as Selective Reflecting Mulch, or SRM for short). It is similar to black plastic mulch used frequently by growers to help warm the soil, prevent erosion, and retains moisture. The red plastic mulch is often thinner than most black weed block and allows more light (and sometimes weeds) through it.
But red plastic mulch’s true strength is in its ability to reflect certain red light waves back onto the growing plant, thereby accelerating fruit production and increasing overall yields. Past ARS work showed that red plastic mulch produced larger tomatoes and produced 20% more than black plastic mulch counterparts and the red plastic mulch also sweeter-smelling, better-tasting strawberries.
Similar results were found on peppers and eggplants as well as with lettuce.
ARS’ also tried the red plastic mulch with cotton, carrots and basil. They found that color of the plastic mulch can affect the roots, stems, leaves and seeds, as well as the fruits, of many other food and crop plants.
Research on cotton showed that cotton fibers grew longer in bolls exposed to increased FR-to-red light ratios. Another study, on carrots, showed that concentrations of nutrients and compounds such as vitamin C and beta carotene in the roots of food crops could be changed by reflecting the right waves of color onto the plants’ leaves.
What’s more, in studies with basil, the amounts of blue, red and FR light reflected onto developing leaves affected their size, aroma and concentration of soluble phenolics. The phenolics are natural compounds, including tannins and pigments that can induce color, some flavors and odors, and antioxidant activity.
Basil leaves developing above red mulches had greater area, succulence and fresh weight than those developing above black mulch. When grown above yellow and green mulches, basil leaves developed significantly higher concentrations of aroma compounds and phenolics than did those of plants grown above white and blue mulches.
The concept of colored mulch sprouted when Kasperbauer wondered whether phytochrome was equally distributed in leaves. He became curious about what would happen if light impinged on the leaf’s lower, rather than upper, surface. “The plant response was the same, no matter which surface received the light,” says Kasperbauer. “Although that experiment seemed somewhat unconventional in 1962, it became highly relevant about 22 years later, when we determined that red and FR reflected from the soil surface could act through the plant’s phytochrome system to enhance yield and quality. That led to our colored-mulch work.”
Red Plastic Selective Reflecting Mulch (SRM) helps to Deter Nematodes
What’s more, tests done by USDA’s plant physiologist Michael J. Kasperbauer and Clemson University nematologist Bruce Fornum showed that nematode damage can be lessened by red plastic mulch. They did an interesting study where they planted tomatoes into sterile soil — some rows covered in black plastic mulch and some covered in red plastic mulch. They then inoculated both rows with 0-200,000 nematode eggs. Their findings showed the black mulch produced 8 pounds of tomatoes whereas the red mulch produced 17 pounds! That’s roughly a 113% increase in yield battling the same conditions.
USDA’s Agricultural Research Service found that red plastic mulch suppresses root nematode damage to tomatoes because the light reflection keeps more of the plant’s growth above ground. The plant’s energy goes into developing fruit and foliage, rather than roots. Nematodes feed on roots. The far-red light reflection to the above-ground plant draws away nutrients from the roots – and nutrients away from the nematodes. Fewer roots mean less food for nematodes. Less food = fewer nematodes.
Things to Consider When Using Red Plastic Selective Reflecting Mulch (SRM)
- Carefully secure red plastic selective reflecting mulch underneath your plants so that there is at least a foot on every side of the plant in it’s mature stage of growth.
- Do not place the red plastic selective reflecting mulch in walking paths as it is thinner than other weed blocking materials.
- Consider placing a weed block material underneath your red plastic SRM to help limit weeds from growing underneath.
- Drip irrigation will be necessary underneath
Two other Bonus Tips for Boosting Flavor in Tomatoes:
- Place 1-2 TBSP of pure natural Molasses in a gallon of water and stir well to dilute it down and place into a spray bottle and spray your leaves. This will aid in bringing out flavor in your tomatoes.
- When your tomatoes are about 18″ tall, a little bit of stress at times can really boost flavor as well. Spray your plants about every 2 weeks with 1 standard strength 325 mg uncoated aspirin tablet mixed in a gallon of water and mix well until the aspirin is completely dissolved and then spray the tomato leaves with the aspirin solution (Salicylic Acid) to trigger tomato defenses. This will especially really beef up your Beef Steak varieties and boost the flavor profile as well.
Find Red Plastic Selective Reflecting Mulch for your Tomato, Pepper, Eggplant, Basil, Cotton, and Lettuce (and more) Crops
• “Colored Mulch Can Help Cotton, Carrots—and Basil, Too” by Luis Pons
September 5, 2003 https://www.ars.usda.gov/news-events/news/research-news/2003/colored-mulch-can-help-cotton-carrots-and-basil-too/
• “Review: Red Plastic Mulch for Tomatoes –Does It Make a Difference?” http://www.tomatodirt.com/red-plastic-mulch.html
• “More than Meets the Eye: New Findings on How Mulch Color Can Affect Food Plants” USDA ARS Online Magazine Vol. 51, No. 9
• “Color of Light Reflected to Leaves Modifies Nutrient Content of Carrot Roots” by George F. Antonious* and Michael J. Kasperbauer USDA
• “Colored Mulch Starves Nematodes” USDA agresearchmag.ars.usda.gov/ar/archive/1997/oct/mulch1097.pdf