The Pros and Cons of Mulching

Mulching is the practice of covering the soil around the vegetables and plants you want to grow.  This is done to boost the various natural processes that help growth and to suppress weeds.  It’s something that nearly all organic textbooks recommend and is amazingly easy to incorporate into any garden system.  So why do more of us not mulch around our plants?

Mulching can be done in several ways: organic matter (such as woodchip, straw or leafmould) can be placed around plants and will eventually rot down into the soil improving its structure.  Alternatively, sheet mulches (such as cardboard or permeable black plastic) can be used or even more permanent materials (such as slate, stones or gravel), although the latter are only usually used for low-maintenance ornamental areas.

The benefits are:

• Mulches suppress weed growth
• Mulches retain moisture - particularly helpful in hot summers
• Mulches reduce soil erosion – useful during winters and heavy rain
• Mulches can insulate crops from extreme temperatures – especially useful for early and late crops
• Organic mulches can rot down to provide soil nutrients and encourage beneficial soil organisms and worm activity
• Mulches can be used to prevent some crops rotting (such as strawberries) by lifting them off the ground

There are some things to be aware of too:

• Mulches can be homes to pests, although combining with other good organic practices should minimise this
• Organic mulches usually need to be applied in a loose or partially-rotted state or the first stages of decomposition, otherwise they can lead to nitrogen being taken from the soil, or anaerobic decomposition which can lead to ‘sour mulch’ which turns acidic and damages the plants it is supposed to be protecting. 
• Organic mulches usually need to be quite thick - generally a good 1 to 3 inches thick placed around plants; more if the mulch will rot down to something smaller.

I’ve been growing poached egg plant (Limnanthes douglasii) in huge quantities this year.  Apart from having wonderful flowers that attract bees and other beneficial insects, it makes an excellent ‘green manure’ to dig into poor quality sandy soil.  After clearing one area I was just about to dig it into the ground when a gardening friend suggested I use it as a mulch around my sweetcorn.  So, I now have most of my sweetcorn duly mulched, with a few left without to compare with (I always like to run little ‘experiments’ like this in my garden to learn from). 

I have also been growing the wonder-plant comfrey next to my compost bin, which has leaves rich in nitrogen, phosphates and potash.  Once harvested and dried, these will be used for mulching around hungry fruiting plants such as tomatoes and peppers to suppress the weeds and feed the soil.  And finally, I have a big bin of rotting leaves turning into leaf-mould which makes an excellent cover around plants – not rich in nutrients but very good for soil structure and weed suppression.

My big problem with mulches is generating enough organic material to do it well.  It’s like compost – fantastic in theory but you never seem to have enough to go round.  I’d love to hear what you do to generate good mulches and what successes you’ve had, so please do add a comment below.