We are experiencing unusual weather patterns; extended droughts or deluges of rain seem to be occurring more frequently. How can gardeners cope with these alternating extremes? There is a simple answer; plenty of mulch.
By way of introduction I have an allotment in Kettering, Northamptonshire, one of the driest areas of the country. The soil is quite heavy clay loam on my plot, with limestone bedrock underneath. I have tended the plot for 25 years and gradually adopted a no-dig approach using thick mulch with great success. My crops grow well in both droughts and deluges.
In the summer of 2018 we experienced many weeks of hot dry weather. I did not irrigate any of my crops and only used a small quantity of the rainwater I had collected to apply liquid feeds or transplant seedlings, such as leeks. The crops were successful and yields high. Instead of watering I mulch heavily. Mulch prevents evaporation from the soil surface and plant roots grow deeper to seek out the moisture that was in the soil from winter rain and snow.
Mulch needs to be thick, ideally 10-15 cm between established plants. With small seedlings the mulch cannot be that thick initially, but as soon as they are big enough add more mulch to get the required depth.
Mulch is added in layers and my technique is sometimes referred to as lasagna gardening. I started using this method of mulching to reduce the time spent on weeding and discovered that I didn’t need to dig or irrigate, so it has three amazing benefits. No digging, much less weeding and no watering.
The first layer to go on the soil is often cardboard or newspaper. Use whole newspapers overlapping, not just a single sheet or thick plain brown card. This layer blocks the light, kills any weeds present and prevents weed seeds germinating. A layer of card will soon break down and blow away so needs more layers on top to secure it and make an effective mulch. There are many suitable materials for these layers including:
- Grass cuttings
- Pulled-out weeds
- Shredded prunings
- Wood or bark chips
- Tree leaves
- Weed-free compost
- Anything else that will decompose sensibly in a compost heap. For example if you have access to a wheelbarrow full of banana peels, comfrey leaves, coffee grinds or tea leaves that would be great.
Things that are less suitable for mulches include:
- Weeds with seeds. Late in summer some weeds have started to flower and seed. These seeds may germinate in the mulch. You can reduce the risk of the weed seeds germinating if you place them underneath a thick layer of card, then use other mulch on top of the card to smother it.
- Pernicious weed roots such as bindweed or couch grass (between November and March). These roots may re-grow and spread the weeds. You might have to dispose of these in your municipal green waste. However, most roots will not re-grow if placed on top of card in the mulch between April and October in dry weather and exposed to the sun and wind. The roots will dry out and die quickly.
- Be cautious about manure. This often contains many weed seeds, so adding this manure may give rise to many weeds. Again, best to put manure underneath a thick layer of card, then other mulch on top of that to smother it.
Finding enough mulch for a thick layer is the main challenge. I have found several sources, including friends who mow their lawns and don’t want the clippings, mowing the tracks and paths around my allotment and buying straw in bales from local farmers. Perhaps your allotment has a corner that is less productive or difficult? Consider sowing grass and clover and mowing it or planting comfrey or other green manure as a source of mulch. Why not offer to mow the tracks and paths around your allotment field or offer to clean up an untidy corner and start mowing it? Are there vacant plots on your site; perhaps you can offer to mow them? That way you get the benefit of the grass cuttings for mulch and the allotment site looks better for everyone.
Mulch can be applied at any time of year. In autumn and winter, instead of digging, I mulch. Most crops are planted straight through the mulch by making a hole into the soil below, for example potatoes or courgette seedlings. In spring and summer I mulch between crops as they establish. Once a crop is harvested I mulch the ground to prevent weeds germinating.
A few weeds still find their way through the mulch but if the mulch is thick enough they are easily pulled out and then simply dropped back on top of the mulch where they wilt and decay. They instantly transform from being a liability to being an asset!
Lasagna gardening could be re-named the horizontal compost heap. In a traditional compost heap, material is added in layers and ideally there should be a balance between “brown” and “green” waste. “Brown” waste has a high carbon content, such as card, straw, woody material and “green” waste has a higher nitrogen content, such as nettles, grass clippings or comfrey leaves. These principles apply to lasagna gardening just like a compost heap. If your mulch is “brown” then you will need to “feed” your crops with a high-nitrogen fertiliser. A liquid fertiliser gives a quick boost if crop leaves look pale green. Fertiliser such as growmore or blood, fish and bonemeal added to the hole when planting your crops is also a good idea if your mulch is very woody or high carbon.
Another way to mulch is to buy weed control fabric. This is woven black plastic. Be sure to get the high quality 100gsm (grams per square metre). If thinner plastic is used it will shred in the first gust of wind; if non-woven plastic is used it may kill weeds, but does not allow rain through. 100gsm woven weed control fabric will last for many years. Weed control fabric is excellent at weed control on its own, but if a thick layer of organic mulch, such as straw or pulled-out weeds it placed on top the benefits are much greater. The pulled out weeds will die and rot, becoming compost; they will weigh the fabric down, reducing the chance that it will be blown by the wind; they will protect the black fabric from the sun’s rays, so extend its life; they will insulate the soil and retain more moisture, so no need to water crops. The weed control fabric can be placed directly on top of a weedy patch, so no need to remove the weeds or dig as they will die, decay and improve the soil fertility. Small holes can be cut through the fabric to plant seedlings at intervals or the fabric can be placed in a strip between rows of crops.
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