Brick red-dyed mulch is the equivalent of the 1970s orange shag carpet. It was popular for about two minutes and then became the ultimate downer after the fad passed. While these colored wood chips are still around, there are many natural-looking alternatives available.
Mulch is a term applied to anything you spread out on top of the ground from straw to wood chips. While these mulches are organic matter, they’re not suitable for tilling into the soil and can actually reduce overall fertility if you do. In fact, the best mulches are made from woody organic matter that resists decomposition so it remains effective for a very long time.
When soil is covered with mulch, three good things happen. First, the earth is perpetually shaded from the hot summer sun, keeping its surface temperatures low so plant roots don’t heat up. Cool roots reduce the plant’s moisture demand so you don’t have to use as much water to keep it healthy.
Second, mulches seal in the water. This layer keeps moisture from rapid surface evaporation in the summer (direct sunlight quickly dries the soil surface). A mulch makes sure every drop you apply is used to its greatest extent by plants. When there isn’t any drying between water applications, plants don’t suffer the wet-dry yo-yo effect that occurs with fully exposed soils. Where soil is predominantly clay, mulch helps to prevent surface cracks that expose roots to air and cause uneven water penetration when you water.
Third, mulch blocks sunlight from direct exposure to soil around plants where weed seeds often sprout. Weeds are successful because they are opportunists adept at robbing other plants of soil moisture. With mulch in place, weed seeds still germinate, but the seedling dies quickly if the new shoot doesn’t reach sunlight. Controlling weed development with a mulch is key to ensuring there’s no competition for water.
It is a rule of thumb that mulch needs to be at least 2 inches deep to provide these three benefits. Mulch layers can be thicker, particularly when using fluffed up material like baled straw because it gradually mats down from watering or being walked on. But don’t pile mulch around the base of any plant, be it a tree or a tomato, or you risk rotting the stem and killing the plant.
Mulches can be decorative or practical. That red dyed wood chip mulch is supposed to be a decorative choice for beds and borders, but it’s not a natural color. Chips allowed to weather to a more appropriate hue or earthy ground bark is a much better choice.
When you select a practical mulch, it should be both cheap and plentiful. You can use bales of alfalfa or grass hay that are more expensive, but if you inquire about spoiled bales, which can no longer be used for livestock, they are much cheaper or sometimes free at feed stores. These compacted bales are easy to transport and fluff up to an incredible amount. Unlike other mulches, alfalfa hay contains nitrogen, which adds some benefit to the soil.
Now that the soil is fully warm in the vegetable garden, it’s OK to apply mulch if the soil isn’t soggy. Warm soil temperature is important for seeds and seedlings to enjoy a vigorous start. They’ll slow down if cool soil is shaded too early in the season. Now that temperatures have spiked and if the surface soil dries out by day’s end, it’s a good time to apply mulches.
Not only will you conserve water, but you’ll have fewer weeds to pick and plants will retain their vigor over those dog days of summer to come.
Maureen Gilmer is an author, horticulturist and landscape designer.