Mulching vegetable gardens: best type of mulch & instructions

Mulching in your vegetable garden is an excellent way to save water and improve soil health. The many aspects to mulching in your vegetable garden are described in detail in this article.

Bare exposed soil isn’t appealing to most gardeners, nor is it often found in nature. In most climates, plants will start to grow in order to cover, protect, and hold exposed soil in place almost immediately. In our vegetable gardens we have a propensity to remove the “weeds”, which are really just plants out of place, in an attempt to help our focus plants grow and reduce competition. This leads to patches of bare soil. Therefore, by mulching in your garden, you can reduce the germination of seeds of unwanted plant species and improve the aesthetics of your garden by eliminating the bare soil.

Should you mulch a vegetable garden?

The simple answer is yes, mulching is very important in a vegetable garden. There are, however, advantages and disadvantages depending on the material used, as well as how and where it is applied. There are four main benefits to mulching your vegetable garden: improving soil health, conserving natural resources, controlling the germination of unwanted plants, and improving aesthetics.

Advantages to mulching vegetable gardens

• Soil protection and water conservation: Mulch provides a cover layer that helps to reduce erosion from water and wind. Mulches also can help to insulate and increase soil temperatures in winter, while in the summer, shading the soil and decreasing evaporation, thereby maintaining a more consistent moisture level and cooler soil temperatures. By covering soil with mulch, you also reduce the formation of hard crusts brought on by water evaporating off the bare soil which is baking in the sun.
• Soil health: While mulch provides a protective layer for your soil, it also provides a protective layer for your soil microorganisms, which are very important in soil health. Soil microorganisms are vital for the nutrient cycle in the soil. They also churn the soil and keep it loose and friable, making it easier for the gardener to cultivate the soil. Depending on the type of mulch you choose, microorganisms will also break the mulch down and add to the nutrient levels in the soil.
• Unwanted plant control and aesthetics: While many gardeners do not like “weedy” overgrown gardens, bare exposed soil isn’t very nice to look at either. Mulch solves both problems. The many small seeds found in the soil will struggle to grow through a thick layer of mulch. Also, mulch reduces the light that transmits through to the soil, which is needed by some seeds to germinate at all.

Disadvantages to mulching vegetable gardens

• While mulch is good at preventing the growth of unwanted plants, it can also be detrimental to the growth of tender herbaceous focus plants and young seedlings which will struggle with heavy mulch layers. It is best to pull the mulch slightly away from these plants, so they have good air circulation and room to grow and develop.
• Mulches made of thick, heavy organic matter like wood shavings and bark can, in the short term, rob vital nitrogen from the soil while the microorganisms break down the mulch.
• Some mulches have to be removed in order to manually cultivate your garden soil.
• If the wrong mulch material is chosen, unwanted seeds of plants may be spread throughout your garden. It is best to use plant material without seeds as a mulch for your garden.
• Some pests, like slugs and snails, can benefit and find refuge from mulch layers too. So, when mulching, keep an eye on your tender, low-growing plants like strawberries (Fragaria) and lettuces (Lactuca sativa).

What vegetables need mulch?

Most vegetable plants will benefit from mulching, especially those that grow high off the ground and do not offer much shade for their soil. These include nightshades like tomatoes (Solanum lycopersicum), aubergine (Solanum melongena), and potatoes (Solanum tuberosum), as well as beans (Phaseolus vulgaris) and climbers like cucumbers (Cucumis sativus). Low-growing plants, like courgettes (Cucurbita pepo var. pepo convar. giromontiina), pumpkins (Cucurbita), and strawberries, also benefit from mulching. Mulches, as they protect the soil from erosion, also stop soil from splashing onto the leaves and fruit of low-growing plants. This stops the transfer of some fungal diseases, and keeps the fruits and leaves cleaner so they can absorb as much sunlight as they can.

It is best to keep mulch away from plants that come from dry Mediterranean climates, as the excess moisture can lead to fungal diseases and rot. This includes plants like rosemary (Salvia rosmarinus), lavender (Lavandula sp.), and other herbs. Members of the Allium genus like garlic (Allium sativum), onions (Allium cepa), and leeks (Allium ampeloprasum) can also benefit from mulching, but one must be careful as they need a dry period to trigger nutrient transfer to their bulbs.

When should I mulch my vegetable garden?

When you should apply mulch to your vegetable garden depends on which functional aspects of mulch you want to take advantage of. If you want to use mulch to prevent weeds in your garden, the best time to apply is early in the spring before seeds have a chance to germinate. This also helps to maintain moisture levels in your soils as temperatures begin to rise. It is also important to mulch your beds after planting them.

When direct seeding to start your vegetables, it is important to wait until your seeds have germinated and are growing into healthy plants before you apply mulch. As was stated earlier, mulch layers will slow seedling growth and even prevent some seeds from germinating. Tender, young vegetable starts can also be susceptible to fungal growth and microorganisms that help to break down the mulching products. Avoid direct contact of your plants to the mulch by leaving an air gap to keep the plants healthy and happy.

What type of mulch is good for vegetables?

There are many different types of mulches that can be utilised in your vegetable garden. The best mulch for your vegetable garden is the type that is readily available to you, and works with your garden management practices. There are two basic types of mulches, biodegradable, which will break down over time and feed your soil, and non-biodegradable, which will not break down. Keep in mind, when applying any organic matter to your soil, or as a mulch, microorganisms require nitrogen to break down the carbon in the organic matter. So, heavier carbon mulches, such as wood chips or straw, will take away large amounts of available nitrogen from the soil. It may, therefore, be necessary to add some nitrogen fertiliser to the soil when you mulch to help balance this. Our Plantura Tomato Food is a good choice for this purpose, as it is slow-release and long lasting so it becomes available as the mulches break down. The following are some of the most popular mulches used in gardening.

Biodegradable mulches

Lawn cuttings and grasses

Lawn cuttings and grasses make great mulches. They are usually tender and have a relatively high nitrogen content. So, when being broken down, they won’t consume all the available nitrogen in the soil. It is best to let your clippings or grasses dry out a little before you apply them as a mulch. Otherwise, they can form a thick mat that is susceptible to rot and mould. Apply your clippings and grasses in a thin layer of around 1-2cm. This layer will break down quickly or be spread thin by wind and animals. This is ok, as you can reapply regularly, as needed, throughout the growing season. It is important to note that your clippings and grasses do not have seeds. If you let your lawn grow too much between mowing, seed heads will develop. If you then go and spread this in your garden, you will be applying grass seeds to your garden, which will cause issues when they germinate.

Straw

Straw is a widely used mulch for vegetable gardens. Its loose structure usually allows for plenty of airflow while reducing light infiltration to the soil. It is also readily available and inexpensive. It does have less nitrogen then grass clippings and straw, so can use some nitrogen from the soil as it breaks down. Straw is a good choice for many different plants and can be pulled away easily if cultivation or replanting is necessary. One drawback to straw is it has a light colour and will reflect light. This means, in the spring, it doesn’t do as good a job warming the soil as a darker, richer, heavier mulch does. It is best to apply straw as a mulch in the spring after the soil has warmed up and while you are planting starts in your garden.

Pine needles

Pine needles, or pine straw is a great vegetable garden mulch. If you have pine trees around where you can collect them yourself, all the better. While straw and grass clippings can compact and cause issues in heavy rain, pine needles form a nice mat that is resistant to decay. As they break down, they also help to lightly acidify your soil. This is great for plants that love acidic soil, or for areas where your soil is too alkaline.

Nettles

Nettles (Urtica), while considered weeds by some, are amazing plants. If you are fortunate enough to have them growing in your garden or nearby, they can be an excellent mulch for your garden. They are naturally high in nutrients, so go ahead and clip them and lay them around your plants as a mulch. Like grass clippings, nettles also won’t consume all the readily available nitrogen from your soil, and as they break down, they will in turn, feed your soil. Be careful to harvest the nettles for mulch before they go to seed. Otherwise, you will be spreading nettles throughout your garden where you may not want them.

Sheep’s wool

Wool is a wonderful product. It is high in nitrogen, a great insulator, and is a deterrent to some insect pests like snails and slugs. It makes a great mulch layer in your garden. However, it can be quite expensive unless you find it as a waste product.

Compost

Composts of various types make great mulches. Typically, commercially-composted products go through a heat sterilisation process that kills most pathogens and plant seeds. This makes for a wonderfully nutrient-rich material, high in organic matter, that feeds your soil and plants while maintaining moisture levels and reducing the germination of unwanted plants. You can find various products on the market from mushroom compost, heavily composted manures, to composted garden clippings and waste products. Keep in mind though, most of these products can have a high level of nitrogen and other nutrients that may not be suitable for light feeders like many herbs and Mediterranean plants. It is also important to note that many home-composted materials will not have been exposed to sufficient temperatures to kill pathogens and weed seeds. Caution must be taken when using home made products so as not to spread diseases and unwanted plant seeds.

Non-Biodegradable mulches

Mulching films and landscape fabrics

Non-Biodegradable mulches are quite useful in the right space. Mulching films and fabrics are used in commercial agriculture quite frequently. They are also heavily used in professional landscaping. They do a great job as a barrier to unwanted plant germination, last a long time, and are relatively cost effective. The drawbacks are that they are usually made of plastic or plastic material, they are not easy to apply, soil cannot be cultivated unless they are removed first, and at times, they can also be a barrier to water penetrating into and evaporating from the soil.

Rocks and gravel

Rocks and gravel make an excellent mulch and are quite pleasing to look at, and they last a very long time. The drawback again here is that they will need to be removed to cultivate the soil or plant new plants. Also, in time, the rocks will sink into the soil. Temperatures can be an issue at times, as rocks and gravel will absorb sunlight and radiate heat. In the summers, this can be excessive for some tender plants growing in exposed locations in the full sun.

Mulching vegetable gardens: step-by-step instructions

• Prepare the area to be mulched by removing any unwanted plants, and raking the area smooth.
• Moist soil will adhere to the mulch better, so if your soil is too dry, give it a watering before mulching.
• To effectively prevent “weeds” from growing, mulch layers need to be between 5 – 10 cm thick. This provides an adequate reduction of light to prevent many seeds from germinating and creates a layer thick enough so that many seedlings will expend all available stored energy trying to grow through the layer up toward the light. As mentioned earlier, grass clippings and green mulches should be applied in a thinner layer, less than 2 cm, to prevent matting that will rot and cause issues.
• When mulching with a high carbon source like straw or wood chips, it is important to provide nitrogen from a slow-release long term fertiliser like our Plantura Tomato Food
• Ensure that the mulch is not in direct contact with any of the stems of your plants. Leave an air gap to keep your plants growing healthy and strong.
• When you have finished spreading the mulch, you can water it in your bed, which will help the mulch settle and hold in place.
• After some time, you will notice your mulch breaking down, or being moved around due to wind or rain. Reapply when necessary to keep a consistent layer over your soil.

Tip: Soil in your greenhouse and raised beds can also benefit from mulching. Follow the same steps as above for these areas, taking care that your mulch layer isn’t much taller than the edge of your beds to prevent spill over during watering.

Want to learn how to make your own compost to use as a mulch or soil amendment? Check out our detailed article for all the tips and tricks!