Mulch is a layer of material placed on the soil around plants to help keep them healthy and strong. The material used depends on a range of factors such as the types of plants, the soil makeup and the local weather. You can use mulch on your outdoor vegetable garden, on raised beds and on your container plants.
There are two basic kinds of mulch: organic and inorganic. You can make your own mulch or buy it in bulk from a local nursery or in bags from online stores.
Once you learn about the benefits of mulch, you’ll understand why professional gardeners would never have a vegetable garden without it.
Before we get into the details of the different types of mulch, let’s first look at the many benefits of mulch and why you should use it in your vegetable garden.
Benefits of Mulch
Keeps Weeds at Bay
Weeds take up precious water and nutrients from the soil that are needed by your growing plants, so keeping weeds to a minimum is essential. A layer of mulch will help to keep sunlight from reaching the weeds below the surface, thus preventing them from growing. But, even with mulch in place, you’ll still get a few weeds popping up, so make sure you check weekly for any stragglers that need to be pulled up. It’s important to be careful when buying mulch as some may contain weed seeds.
When it comes to moisture in the soil, mulch works both ways to keep moisture levels stable, so that it is neither too wet nor too dry. On rainy days, mulch absorbs the surplus water and releases it slowly into the soil over time. On the other hand, when rain is infrequent and the days are warm, mulch helps prevent evaporation and keeps the soil from drying out.
Moderates the Soil Temperature
Rapid changes in soil temperature can play havoc with your plants and their tender roots. Mulch acts as an insulating layer, slowing down the temperature changes while keeping the soil cooler in summer and warmer in winter.
In addition, your winter vegetable plants will have a degree of protection from frost and be stronger and healthier overall.
And in hot weather, when the sun can bake the soil and prevent moisture getting through, the barrier that mulch provides will prevent that from happening.
Adds Nutrients and Organic Matter to the Soil
If you use organic materials such as leaves or wood bark for mulch, they add nutrients to your soil and improve its structure as they break down, which helps prevent disease. A healthy soil should be made up of about one third organic matter.
Erosion Control (Keeps the Surface of the Soil Intact)
Although this may not be the first thing that comes to mind when considering mulching your vegetable plants, wind and rain can do a lot of damage to the surface of your soil. A layer of mulch will prevent erosion and keep your soil intact and it also prevents compaction by heavy rain fall.
Reduces the Risk of Plant Disease
Plant diseases start in the soil but usually only thrive if they’re able to reach the foliage above ground. This can happen when the soil is disturbed by rain and direct watering. With mulch, water seeps slowly into the soil without disturbing it, keeping the pesky pathogens in their place below ground.
Many people use mulch, for example cedar chips, simply to improve the appearance of their garden. So, it’s worth keeping in mind, if you have a choice of mulch material, to consider if the look is pleasing to the eye. Admittedly, this is probably more important with a flower garden than with a vegetable garden.
Recycling of Materials
Many of the materials that make up mulch are ones that otherwise would be considered “waste” and end up in landfills. So, by using organic mulches like leaves and wood chips, you’ll not only be enriching your soil, but you’re helping the environment at the same time.
Organic mulches come from nature and break down over time while improving the nutrition and composition of the soil. Many organic mulches are simply garden waste that would otherwise be thrown away.
Always choose an organic mulch for your vegetable garden. Your fruits and vegetables will benefit from the nutrition in the soil, and your family will be safe from harmful chemicals.
Leaves are a favorite of some gardeners since they’re free, they look quite nice and they break down over the summer, just in time to be mixed in with the next addition of compost before winter arrives.
Once collected in the fall, the leaves will need to be shredded. You can do this with a lawnmower that has a collection bag attached and, hey presto, your compost is ready. But, make sure to allow any wet leaves to dry out before shredding. You’ll need somewhere to store the shredded leaves until the spring, unless you’re planting winter vegetables.
Wood chips and shredded bark are inexpensive and have an aesthetic appeal, especially when they are dyed an attractive color. A common concern is that chemicals from the dye can seep into the soil, but this is generally not an issue, since most dyes these days are made from soy products. However, it’s still a good idea to check what dye is used before buying.
Because wood chips and shredded bark break down slowly, they are not the best mulch for annual vegetables. At the end of the season, you’d be mixing wood pieces into your soil which would probably not be an improvement. This type of mulch, however, would be excellent for perennial vegetables like asparagus and garlic, and perennial herbs like rosemary, thyme, sage, oregano and mint.
Straw or Hay
Straw and hay are easy to work with but are not as attractive as other mulches. This, however, may not be an issue with a vegetable garden. Straw and hay both break down quickly, although straw is a bit slower to decompose than hay.
Straw comes from harvested crops like wheat, barley and oats and typically does not contain weed seeds. Hay on the other hand comes from grass or other herbaceous plants and may often contain seeds. Both straw and hay can have residues of pesticides or herbicides, so be careful to check where the mulch was sourced before buying.
You will, of course, need to have a lawn – or a friendly neighbor with a lawn to give you their grass clippings. And you’ll find it easier if your lawn mower has a bag attachment. Once collected, lay the clippings out to dry for between a few hours and a day, before spreading over your soil (you may need to place plastic over them to stop them blowing away).
To apply grass clippings, spread just a thin layer at first, then add another thin layer every few weeks. If you add the clippings more thickly all at once, they will mat down and you’ll lose the benefits of using a mulch.
A benefit of grass clippings, in addition to the fact that they’re free, is that they contain nitrogen and potassium, a nice addition to help fertilize your soil.
Pine needles are inexpensive and don’t wash away as easily as some other mulches, so if you live in an area with heavy rain, this might be a mulch for you to consider. They break down more slowly than some mulches and therefore don’t need to be replaced as often. This can be a benefit for perennial plants, but not so much for annuals when you want to mix your mulch into the soil in preparation for the winter.
Since pine needles are thin, they are not perfect at blocking out the light and are therefore not as effective at keeping weeds at bay as other mulches.
A word of caution: be careful to protect yourself with gloves and long sleeves when working with pine needles.
Shredded Paper and Cardboard
If recycling newspapers is your thing, this is an option to consider. These days, newspaper ink is soy-based so contamination is generally not a problem.
One option is to shred the newspaper or cardboard, but unfortunately this type of mulch doesn’t look particularly attractive and it does get soggy, so for those reasons it’s best used in a covered area such as a hoop house.
The other option, which is much easier and faster, is to place sheets of newspaper straight onto the soil, making sure there are enough holes for water to pass through. Two or three layers of newspaper should be enough. You can cover the newspaper with a layer of straw to make it look more attractive. The weight will also hold the sheets down.
Inorganic mulches such as plastic sheeting, carpet remnants and rubber are not recommended for growing fruits and vegetables.
These materials can increase the temperature of the soil and they do nothing to increase the nutritional content. Moreover, they may contain any number of chemicals that could get into the soil and eventually into your fruits and vegetables.
When and How to Apply Mulch
The best time to mulch around new plants in your vegetable garden is right after planting them. Generally, a 2- to 3-inch layer of mulch is the right amount, enough to prevent weeds from forming and not so much that water can’t penetrate. It’s a good idea to keep a 1-inch space around the stems of plants so they don’t rot.
As for newly planted seeds, unless you’re using a light mulch like straw, hold off on the mulch until the seedlings are a few inches above the ground. And of course, the soil should be cleared of any weeds before mulching.
Dyed or Colored Mulches
As mentioned earlier, most dyes these days are made from soy products. However, some mulches may contain older woods that contain chemical dyes that are no longer legal or safe to use. So, if you can’t ascertain for certain where a colored mulch comes from, it’s best to simply to avoid it, especially if using it in your vegetable garden.
Although indoor plants are not faced with some of the hazards that growing outdoors poses, your indoor plants will definitely benefit from a layer of mulch. In addition to keeping the soil moist, they will look so much better too. After all, who wants to look at “dirt” in their living room?
You can be a little bit creative here and use materials such as small stones, pebbles and shells. But, your fruits and vegetable plants will benefit more from fine organic mulches specifically designed for pots.
Your budget and how you want your vegetable garden to look might be a determining factor when choosing a mulch. But, for annual plants, the faster decomposing mulches like leaves and grass clippings are probably best. And you can of course experiment every year with different mulches to find the one that works best for you and your crops.
This University of California article Mulches for Landscaping goes into more detail on the science of mulching and has a chart on the benefits and problems with various mulch materials used in landscaping.