I read with interest your article in the telegraph last September and have kept the cutting ever since. I just wanted to ask you about mulching. Do you mulch everything? If so, what with? I'm particularly interested in giving our courgettes/squash a boost but am not entirely sure how to go about it. We're in the Isle of Man, so would have seaweed at our disposal, also plenty of grass clippings (though my Dad is sceptical about this approach!).
Aalish in Isle of Man on 24 June 2013
I am flattered you have kept that article for so long and delighted you are asking a question.
I am a fantastic fan of mulching and do it to almost everything to some degree or other. I am not keen on the idea of bear ground so almost always cover it with something even if it’s only something like sand to get a better tilth on the ground.
Nearly every plant will benefit from having a little mulch put round it just to keep the ground moist, stop drying out and cracking as well as adding a boost to the plant while it’s growing. The old Chinese system of No Dig is based on mulching. Instead of digging nutrients into the ground and also open up the soil texture they used to put all the organic matter on the top of the soil and let the earth worms do the digging. I am a great believer in this system but I like to get the ground in good order first and then no dig, but that’s another article.
Mulching does many things and it is a good idea to think through what effects there are in the longer term before mulching.
The main benefits are weed suppression, adding bulk and nitrogen or changing the acidity of the soil. Another effect which I often use is to make the top of the soil look nicer and cover up some unsightly part as well as making a nice tilth on top of the soil.
Weed suppression. If the sole idea is to suppress weeds then almost any material will do, even if it has weed seeds in it itself. If the mulch is plant based it will eventually break down. If it had weed seeds in it will leave the seeds behind to eventually germinate, as with your grass. You have to re mulch with more material to stop this germination. You could carry on like this for some time but you have to remember you are building up quite a store of weed seeds. If you are mulching with grass, which is quite acidic but very good for weed suppression, you will also need to put some form of lime or chalk on to correct the increased acidity.
I do use grass for mulching but I only use the first one or two cuts in the spring for this. If you take the grass in February or early March there will be very few weed seeds in it so you have quite clean mulch. I use this to mulch things like my Step over Pears in the vegetable patch. I put a good 4in to 6in of new mown grass under the pear trees and it will last all year. At the end of the year when the grass has gone I add a little chalk to neutralize the effect.
I also harvest clover and use it in the same manner but unfortunately it always has lots of weed seeds. I mulch one year, again 4in to 6in thick and leave it clear the next and hoe to help get rid of the seeds. As the clover dies away it makes a lovely tilth on the soil so hoeing is quite easy.
Adding Nitrogen. Adding a mulch of some plant material will contain quite a large amount of nitrogen and enrich the soil this way. Adding homemade compost is a perfect example. The clover example above will do the same. I add large amounts of Seaweed to my Asparagus bed which acts as a weed suppressor (only to a certain extent) but manures the Asparagus very well. Asparagus is a sea side plant so both the seaweed and the salt on the seaweed are perfect for Asparagus. It also changes the taste slightly. It gradually rots down into the soil.
Changing Acidity. Some plants like it slightly acid or alkaline so adding a mulch of either will change the ph. Strawberries like it slightly acid so adding a mulch of leaf mould (slightly acid) will help change the ph and also help with water conservation.
I am lucky enough to be able to get a lot of oyster shells which I crush and add around brassica plants. Oyster shells are alkaline and so help with the ph and prevention of club root as well as giving the slugs a hard time (unfortunately that’s all as the don’t kill them). Wood ash would do the same.
Water Conservation. Once you put mulch on top of the ground you stop some of the water evaporation from its surface and so help water conservation. Some plants really benefit from this; celeriac is a perfect example as it likes a slightly damp soil. The thicker the mulch the less water evaporation. Courgettes are a great example and I mulch a large circle (3 foot in diameter) of quite course compost round each plant 6in high. I looks quite a lot when the plant is small but the leaves should cover this later on. It does lots of things; helps weed suppression, adds a lot of nitrogen to the hungry plant and aids water conservation. Your courgettes should grow very well if you have enough compost.
I hope this has helped with some of your decisions