Mulching vegetable gardens: best type of mulch & instructions

Eric
Eric
Eric
Eric

I love plants. I have a BSc. in Turf and Landscape Horticulture, an MSc. in Crop Production, and a Ph.D. in Crop Science, as well as over 20 years of experience in landscaping, gardening, horticulture, and agriculture. The central focus throughout my career, has been on caring for the soil, as healthy soil makes for healthy plants, and plants are integral to the sustainability of life.

Favourite vegetables: basil, garlic, onions and leeks
Favourite fruits: ripe figs, blueberries and dates

Mulching in your vegetable garden is an excellent way to save water and improve soil health. Keep reading to learn more about the many aspects to mulching vegetable gardens.

Lettuce surrounded by straw mulch
Mulching improves soil health and when done properly, encourages plant growth [Photo: Lithiumphoto/ shutterstock.com]

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

Should you mulch vegetable gardens?

Yes, mulching is very important in a vegetable garden. That said, there are 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. In the summer, they can shade the soil and decrease 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 that has been baking in the sun.
  • Soil health: mulch provides a protective layer not only for your soil, but also for your soil microorganisms, which are very important for 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 us gardeners 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 of these problems. The many small seeds found in the soil will struggle to grow through a thick layer of mulch. Also, mulch reduces the amount of light that gets through to the soil, which can be helpful as it stops plants whose seeds need light to germinate from growing.
Mulch being applied around nightshades
When mulching in your garden, it is important to leave an air gap between the plants and the mulch [Photo: KaliAntye/ shutterstock.com]

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 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).
Strawberry half eaten near mulch
Mulches can at times harbor pests like slugs and snails [Photo: Isabel Eve/ shutterstock.com]

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. As they protect the soil from erosion, mulches 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 possible.

Courgettes in mulch
Mulching low-growing plants help to keep their fruit clean and healthy [Photo: Christian Storto/ shutterstock.com]

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 be careful, as alliums 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 had 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. To keep your plants healthy and happy, avoid letting the mulch come into direct contact with your plants by leaving an air gap.

What type of mulch is good for vegetables?

There are many different types of mulches that you can use 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 and non-biodegradable. Biodegradable mulches will break down over time and feed your soil. Non-biodegradable ones will not. When mulching or generally applying any organic matter to your soil, keep in mind that 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. Because of this, it may be necessary to add some nitrogen fertiliser to the soil when you mulch to help balance things out. 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. Keep reading to learn a bit more about some of the most popular mulches used in gardening.

Tomato Food, 1.5kg
Tomato Food, 1.5kg
star-placeholder star-placeholder star-placeholder star-placeholder star-placeholder
star-rating star-rating star-rating star-rating star-rating
(5/5)
  • Perfect for tomatoes, chillies, courgettes, cucumber & more
  • For healthy plants & an abundant tomato harvest
  • Long-lasting fertiliser that is free from animal products - child & pet friendly
£12.99

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 to 2cm. This layer will break down quickly or be spread thin by wind and animals. But don’t worry, you can reapply regularly as needed throughout the growing season. It is important to make sure your clippings and grasses do not contain 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.

Grass clippings as mulch
Lawn clippings make excellent vegetable garden mulch when utilized properly [Irina Zharkova31/ shutterstock.com]

Straw

Straw is widely used for mulching 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 is easy to pull away if cultivation or replanting is necessary. One drawback to straw is it has a light colour and will reflect light, meaning that, in the spring, it will not do as good a job warming the soil as a darker, richer, heavier mulch would. 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, are great vegetable garden mulch. If you have pine trees around, you can even go and collect them yourself. 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

While considered weeds by some, nettles (Urtica) 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 a great insulator, a deterrent to some insect pests like snails and slugs and high in nitrogen. Therefore, 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 and heavily composted manures to composted garden clippings and waste products. However, 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 last a long time, are relatively cost effective and do a great job as a barrier to unwanted plant germination. The downside is that they are not easy to apply and are usually made of plastic or plastic material. On top of that, 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.

landscape fabric around vegetable plants
Mulching films and landscape fabrics can also be used in vegetable gardens [Photo: Hans Verburg/ shutterstock.com]

Rocks and gravel

Rocks and gravel make an excellent mulch and are quite pleasing to look at. They are also naturally occurring materials and 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 summer, this can be too much 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 5 – 10cm 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, apply grass clippings and green mulches in a thinner layer (less than 2cm) 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, for instance.
  • 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, water it in your bed to 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.
Mulch being applied around tomato plants
Mulch will adhere better to moist soil than to dry soil [Photo: Jurga Jot/ shutterstock.com]

Tip: soil in your greenhouse and raised beds can also benefit from mulching. Follow the same steps as above for these areas, making sure your mulch layer is not 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!

Subscribe to the Plantura newsletter