Mulching is a very beneficial gardening task, particularly in polytunnel growing. However, out of the 27 million people in the U.K. who indulge in the hobby[i], many of us underestimate its significance. The benefits of using mulch include suppressing weed growth, protecting plant roots, nurturing healthy soil organisms, and reducing your water waste by as much as two-thirds![ii] So, whether you’re growing your bulbs in a polytunnel or the great outdoors, this is everything you need to know about mulch to give your garden a boost this spring.
What Is Mulch?
Mulch is a layer of material or loose covering applied over soil and around plants. Although gardeners generally use mulch to add moisture to the soil and suppress weeds, they can bring many other benefits to a garden depending on the type you use. These include:
- Reducing the need for watering
- Improving soil’s organic matter
- Protecting plants from changing weather conditions
- Helping soils retain moisture
- Deterring pests
- Helping to combat climate change
- Providing nutrients
- Protecting plant roots from extreme temperatures
- Giving the garden a tidy appearance
Different Types of Mulch
Mulch can be made of several different components, though this depends on the type you use. We can separate each type of mulch into two main groups: biodegradable and non-biodegradable.
Biodegradable mulches gradually decompose and break down to release nutrients into the soil. This helps improve the soil’s structure; however, layers of biodegradable mulches need replacing when the current coating has completely rotted down. Since biodegradable mulches are naturally occurring materials, they are an eco-friendly choice. Examples of biodegradable mulches include wood chip mulch, compost mulch and bark mulch.
Since non-biodegradable mulches don’t release nutrients into the soil, they have little effect on the structure and fertility of the ground. Despite this, they do retain moisture and suppress weeds, allowing plants to thrive. Non-biodegradable mulches also look more decorative and attractive than biodegradable mulches. Examples of non-biodegradable mulches include seashells, slate, pebbles, stone chippings and tumbled glass.
|Common Types of Mulch||Where Are They Best Used?|
|Wood Chip/Bark Mulch (Biodegradable)||The type of wood used, the size of the pieces and several other factors will determine how useful wood chip and bark mulch will be for different plants. Since they are low in nitrogen, wood chip and bark mulch is best used on flower beds or vegetable gardens alongside a nitrogen-rich mulch, such as grass clippings or leaf mulches.|
|Straw Mulch (Biodegradable)||Straw mulch is best used around strawberries and similar fruiting plants to help elevate the fruits from the soil.|
|Compost Mulch (Biodegradable)||Although compost and mulch are not the same things, compost does make for excellent organic mulch. Compost is rich in nutrients, so will be best spread around common crops. In a polytunnel, getting into the habit of adding compost whenever a space frees up before planting new crops will be highly beneficial.|
|Manure (Biodegradable)||If available, manure from horses, goats, cattle, or sheep makes perfect mulches. Poultry, rabbits, and small rodents’ waste may also be used but must be composted before use since it can burn plants if added directly.|
|Leaf Mould (Biodegradable)||Leaf mould is an excellent mulch since anyone can make it by collecting fallen leaves and rotting them. Both partially decomposed leaf mould and the finished product can be valuable as general-purpose mulch in your garden and polytunnel.|
|Leaf Mulches (Biodegradable)||There are plenty of green, leafy materials that you can use as a mulch to add slow-release nitrogen fertiliser to your garden. However, using organic, nitrogen-rich material is always a better option. Mulching with weeds (that have not yet gone to seed) is one good example.|
|Grass Clippings (Biodegradable)||Grass clippings that have not been treated with any chemicals can make a great mulch. But it is important to remember that this and other nitrogen-rich mulches should only be used around certain plants. Too much nitrogen can sometimes burn crops. Grass clippings should be used early in the season when crops are starting to grow.|
|Seaweed (Biodegradable)||Seaweed can provide several micro-nutrients that are not as readily available in other plants. As well as retaining moisture and suppressing weed growth, it can help add fertility to your growing areas.|
|Living Mulch (Biodegradable)||A living mulch is a living plant grown to create ground cover between other plants. Examples of living mulches include clovers, alfalfa, phacelia and creeping thyme. You should sow these around annual crops, vegetable gardens, perennial planting schemes, orchards, and sloping sites.|
|Gravel or Slate (Non-biodegradable)||Stone chippings are an attractive mulch choice that works well on flower beds, particularly in smaller gardens. However, soil with stone chipping mulch will require extra watering to ensure enough nutrients and moisture.|
|Rubber Mulch (Non-biodegradable)||Perfect for containers and polytunnels, rubber mulch is long-lasting, low maintenance and non-absorbent. However, rubber contains small amounts of zinc, which may affect certain plants and crops.|
When To Mulch Your Garden
It’s best to apply mulch to your garden in mid-to-late spring and during autumn. Plants will benefit from mulching in spring since weeds will not have taken root yet, and the soil will be warming up, and it is necessary for winter when the plants have begun to die back to protect their roots for next year. However, you can mulch new plants that need to be established at any time of the year since weed suppression and extra moisture will boost their growth.
How To Make Mulch
Depending on the type you wish to use, mulch can cost. However, making your own is simple, cheap and completely eco-friendly. On top of this, making your mulch means you can add whatever you want to it. Leaf mulch is the easiest to make yourself, plus you can mix it with several other biodegradable materials to help boost the growth of your plants, reduce your waste and save the planet.
How To Make Leaf Mulch
- Rake up and collect any fallen leaves from your garden, or gather leaves you have pruned from plants. However, avoid using the leaves of walnut and eucalyptus trees. These can prevent other plants from growing.
- Collect the leaves into a pile on a flat section of the lawn using a leaf blower, rake or shovel. Ensure that this pile is no more than 2 inches thick.
- Use a lawnmower to mow over the thin pile a few times, so the leaves are chopped into small pieces.
- Spread your leaf mulch along your flowerbeds and in your polytunnel as soon as they have been shredded. Any extra mulch can be stored in a large bag pierced with ventilation holes or spread out on a tarp and covered.
- If you’d like, you can add several other mulch materials from the garden to your leaf mulch for added nutritional benefit. For example, chopped up tree branches and bark work perfectly with leaf mulch, as do grass clippings, pine needles, and shredded paper.
Where To Apply Mulch
You can spread mulch across entire flower beds and vegetable gardens. There aren’t many plants that you can’t apply mulch to, but there are specific areas that you should focus on. Pay particular attention to the roots of spring bulbs as the foliage dies back, under hedges, herbaceous perennials that have just been divided and watered, the roots of fruit trees and bushes, and any fruit and vegetables being grown inside your polytunnel over winter.
How To Apply Mulch
Applying mulch is a simple task. Just be careful not to smother low growing plants or pile mulch against the stems of woody plants – this can affect the growth of the plant’s roots and girdle the stem.
- Clean your beds of any debris and old mulch, water them well and pull out any weeds.
- Spread your mulch. Biodegradable mulches must be at least 5cm thick, so lay your chosen mulch onto the bed or around essential plants steadily using a spade or your hands.
- Finally, gently rake or hoe your beds to ensure the mulch is evenly distributed.
- Mulched beds may need watering not long after mulching to ensure moisture reaches the plant roots. After this, they shouldn’t need watering very frequently.
For such a beneficial addition to any garden, mulch needs very little maintenance once you’ve spread it. However, here are some final points to keep in mind once mulch has been laid:
- You don’t have to remove mulch to add fertiliser. Fertilisers can be spread over mulches in late winter and will still reach roots.
- Don’t hoe weeds growing in mulched beds. Instead, remove them by hand and follow this with a layer of fresh mulch.
- A thick layer of mulch will prevent plants from growing. If your mulch is thicker than 6 inches, use a rake to thin it out.
- If you use manure, ensure that it is well rotted. Otherwise, this could scorch plant leaves and distort them.
Mulching is perfect for polytunnel growing since it reduces watering needs and adds fertility to the soil. However, mulch is incredibly beneficial for the rest of the garden too. Different mulches will benefit different plants and gardens, so try a range of materials to find the one that will set you ahead of the rest next spring!
Which mulch do you use in your garden? Share your favourites in the comments below!
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.