Does Mulching Work?

 Thanks to Lori McCarter for the image

Is using mulch around plants and shrubs a good idea?  Like most things in life there are no simple answers, it depends who you talk to.

Personally I would think that generally, yes, mulching around plants is a good idea. There are voices of contradiction in the air though.

What if you put too much fresh mulch like wood shavings around the young plants, would it rot the stems?  Do pests and disease live in the bark put on the paths, were chemicals used in the process that would compromise an organic garden?  I really don’t know and I’m sure we could debate it over many pints in the pub.  

The one thing I would agree with is nature, and how mulching happens naturally in woodlands and wild places.  There’s a balance of decaying matter that helps to both promote new growth and sometimes deter others. Balance, that’s what it’s all about and how we can replicate it in or own gardens.

Mulching

Mulch can be used for a lot of things in the garden.  Some discourage seed germination and help to retain moisture.  During warm weather the soil under cover of mulch stays cooler and retains moisture longer than uncovered ground, which reduces the need for watering. 

I like to think that the best much is free mulch, or as near to free as you can get. So what other benefits does mulching bring?

In winter, heat that rises off the soil is held in place. It's the same as when we sleep under a blanket in an unheated house. During the summer, it's like insulation that keeps the heat out.

Add to its other benefits that mulch aids in erosion control, reduces compaction from rain and foot traffic and releases nutrients.

Some of the biggest criticisms about mulching is that different materials could either steal the earth of nitrogen/put too much nitrogen in the soil, not break down quickly enough and can rot plants. 

I think that these issues are overshadowed, not by the mulch itself, but the materials the mulch is placed on around the plants and on paths.  Non-biodegradable plastic, old carpets with nylon thread that tangle up in the fork are the biggest issues as they can get really untidy and make the ground hard to work.

The amount of nutrients available or how quickly they break down varies a lot with different mulches. Compost is quickest to decompose and one of the most nutrient-rich, so that really wouldn’t need a membrane other than a few sheets of newspaper underneath it.

Newspaper

Regardless of the type of mulch, I’d say put down at least 5 to 10 layers of newspaper before spreading. The newspaper lasts longer than you may think, under wood chips over a weedy lawn it can last up to seven years.  Landscape fabric would do the same but you’ll be picking pieces out of the soil for years. Mulch can be used on paths, but keep in mind it’s different to gravel and will need replenishing annually.

Application

When applying mulch, how much depends on which type you're using. Spread finer-textured products such as yard debris compost or mint compost 2-5cm inches deep. Coarser wood products such as bark dust, wood chips and arborist waste can be as deep as 8-10 cm. Try to keep any material at a few cm away from the base of trees, shrubs and woody perennials.

Some Choices

Bark dust. Good weed control but can tie up nitrogen in the soil so not good for plants that aren't established.

Wood chips. Easily available. Lasts a long time. Good weed control but again can tie up nitrogen.

Bark nuggets. Attractive appearance and easily available. Lasts a long time. Good weed control but again it’s a nitrogen thing. It can be expensive if bought in bags too.

Garden/municipal compost. Good source of nutrients. Locally produced.Can promote weed growth. Doesn't last long so might need to be refreshed each year.

Tree leaves. Free and easily available. Good source of nutrients. Not easy to spread to a consistent thickness. Must be mowed or turned to get it to break down in a season.

Sawdust. Good for vegetable paths. Holds down weeds well. Repels moisture because it's so fine. Fresh sawdust isn’t really good for bedding plants.

Coco hulls. Decorative but could be expensive and a bit dangerous for pets. HUGE carbon footprint coming from the other side of the world.

Stray/hay. Great for keeping the strawberries dry, could attract rodents and be a storage space for weed seeds

Grass clippings. Breaks down well and gives nutrients back to the soil. Could get a bit crusty stopping water getting to the soil and if it’s not yours there might be chemical residues.

Leafmold. Straight from the woods this is a great mulch but can have weed seeds in it. Getting permission to dig some up is a bit tricky sometimes. 

My Conclusion

All in all I think mulching works and helps to improve the health and appearance of the garden, although I must confess, I haven’t done any mulching this year apart from throwing a few comfrey leaves around. I have a covering of chickweed instead.