For our next installment of Garden Blog, let’s discuss Mulch. Most of us know what mulch is, we put it around our trees and around our perennial bushes and shrubs. But, many of us do not know WHY we mulch. For most the main reasons are to keep weeds down and to look attractive. And those are good reasons to mulch, but it they are not the only reason, nor in my opinion, the most important. Many people do not mulch their vegetable gardens, which is a big mistake.
First let’s go over some of the other benefits of mulching. Water preservation is #1. Mulch keeps the sun and wind away from the soil surface, this helps retain water. Dirt alone is very porous, or at least good garden soil should be, but this will lend itself to drying out quickly with sun and wind. Mulch holds a lot more water in the top layer of soil, where for a lot of plants, the majority of their roots are. This is especially important when fruit are setting. Uneven water availability causes fruits to split, crack and even become less flavorful. If the plant is lacking water and then suddenly gets a lot all at once, it will try to store as much as it can, and this often leads to the symptoms above.
#2 on the list, at least if you are using an organic mulch, is soil conditioning. Mulching with dead plant material like straw, grass clippings, shredded leaves etc. will condition your soil over time. Earthworms eat decaying plant material, so a nice 3 inch thick layer of straw is a perfect dinner bell to call thousands of earthworms into your garden beds where they will till and “fertilize” day and night for you. You have to add mulch continually because the worms eat it as it decays, adding the nutrients to the soil and ultimately to your plants. Mulching with heavy wood chips is OK, but they take a lot longer to break down, so soil moisture is preserved, but they don’t quite ring the earthworm dinner bell like faster decomposing mulches listed above.
#3 would be weed suppression. Not only will your mulch suppress weeds, because the soil underneath is moist and soft and fluffy; the weeds that do pop through can be pulled with much greater ease. Some mulch may contain seeds of their own, for example standard hay may have grass seeds and other weed seeds. For my money, the tradeoff is worth pulling a few extra seedlings, but if you really want to avoid it, you can find seed free straw or you can make your own shredded leaf mulch. Just make sure there aren’t any tree seeds present when you make your leaf mulch. I have been pulling little maple trees all spring, not that it’s hard, but it could have been avoided if I raked my pile around the yard a bit to allow the seeds to fall to the ground as the pile was moved.
#4 on the benefit list but certainly not the least is disease prevention. This is especially true for tomatoes, but certainly all plants are susceptible to disease, weather it be bacterial, viral or fungal. When you have heavy rain, or even a heavy hand with the hose, water puddles a bit and mixes with the dirt, then as the water keeps pounding down the splash-up carries soil particles with it. There are some disease problems that are air born or carried by insects, but many others live in the soil, especially the bacterial and fungal varieties. Mulch acts as a splashguard, preventing the water from mixing with the soil and preventing the droplets from hitting the muddy puddles and splashing up onto your leaves.
Ok, so now that we know mulch does a lot more than just block weeds, but when do we add it? The real questions, is when do you not add it. The bottom line is that bare dirt is vulnerable. You should always have at the very least a very thin layer of mulch on bare dirt. If you need to plant into it, you just sweep the mulch away from the planting hole, and then brush it back into place around the new seedling or plant. For areas you have planted with seed, I apply a very thin layer, usually of grass clippings that have been allowed to dry on a tarp for a day or two. They will keep the soil moist longer, usually long enough for the seedlings to emerge and tolerate a heavier layer of mulch. As a general rule of thumb I try to keep my plants mulched at a 3 inch thickness year round. Be sure to also give your empty beds a nice layer of mulch at the end of the growing season for the winter; your soil will be lush and productive for you the next spring. One last thing, do not let the mulch material touch the stems of your plants; a couple inches of space will be fine. Too much moisture around the stems of many plants can cause some other major problems.