Mulch Types for an Organic Garden
Linda, one of the Sustainability Nuts who frequents the Sustainable Living Wise site wanted to know what mulch I would recommend. I was going to tell Linda that it depends on her environment (is her land sloped? is it a small suburban block?) and what she wants to mulch (is it a large orchard? or a small vegetable plot?) because each mulch has its own advantages and disadvantages, and then I would have recommended…
But then LTSH (Long Term Suffering Husband) became involved. And since he’s become the ‘Mulch-o, Mulch-o Man’ there was suddenly a need for more indepth research and detail. So, Linda – here’s the long LTSH answer.
There are a large variety of mulches – from living ones (living plants) and non-living (yup, you guessed it – dead stuff). Here are the advantages and disadvantages of each:
| Mulch | Advantage | Disadvantage |
|---|---|---|
| Bark | Biodegradable | Fine grade can compact and stop water from getting through to soil |
| Takes a while to break down so doesn't need constant topping up | Can come from non-sustainable forestry practices | |
| Has a very natural look to it | Not good on sloped land as it will just slide | |
| Available in fine grade, medium and coarse grade | ||
| Black Plastic | Suppresses weeds | Can cook the soil - deterring earthworms and killing useful bacteria |
| Warms the soil - good for strawberries | Doesn't allow air to circulate and can encourage root pathogens | |
| Not biodegradable | ||
| Doesn't allow water to penetrate all areas | ||
| Expensive | ||
| Can blow around during strong wind | ||
| Bracken Fern | Contains nitrogen, phosphorus and potassium | Difficult to get |
| Untidy | ||
| Breaks down quickly requiring constant top up | ||
| Cardboard | Cheap | May not be the look you want to achieve |
| Recycling | Heavy coloured print can leach into soil | |
| Biodegradable | ||
| Good weed supressor | ||
| Dead plant matter (leaves and twigs) | Airy mulch | May not be able to find enough |
| Full of useful nutrients | Classified as untidy to some | |
| Native plants love native leaf mulch | ||
| Cheap | ||
| Recycling | ||
| Grape Residue | Holds valuable nutrients | Can hold pesticides |
| Disintegrates quickly requiring constant top-up | ||
| May be hard to get hold of | ||
| Gravel | Good drainage | Needs to be added thickly |
| Allows all moisture to get down into the soil beneath | Can be expensive | |
| Insulation protects soil from extreme temperature fluctuations | Doesn't break down | |
| Light coloured gravel reflects sun's rays keeping soil cooler | No nutrient benefits | |
| Darker gravel absorbs sun's heat warming soil | ||
| Won't blow away in strong winds | ||
| Hay | Contains valuable nutrients | If 'spoiled' it can lead to dreadful fungal infestation |
| Biodegradable | Seeds can germinate creating a weed problem | |
| Has been linked to Aspergillosis (fungal infection) in birds | ||
| Can contain herbicides | ||
| Lawn Clippings | Easy to get | If used fresh they will generate heat while decomposing burning plants |
| Cheap | If used fresh they draw nitrogen from the soil while decomposing | |
| Biodegradable | Have to store somewhere to dry (Best used after they've dried) | |
| Living Mulches | Assist other plants as companions | Takes time for plants to spread |
| Add valuable nutrients to the soil | ||
| Roots help to aerate soil | ||
| Cheap | ||
| Feeds animals (bees and any poultry you may have) | ||
| No need to top-up | ||
| Easiest way to mulch a large area | ||
| Helping carbon emissions with more plants | ||
| Lucerne Hay | Contains valuable nutrients | Expensive |
| Medium time for breaking down | Has been linked to Aspergillosis (fungal infection) in birds | |
| Looks good | ||
| Mulch Blocks | Neat | Can be expensive |
| Easy to use | ||
| Choose Coir Product (Coconut Peat which is a renewable source) | ||
| Airy mulch | ||
| Biodegradable | ||
| Newspaper | Cheap | Coloured print can leach into soil |
| Recycling | t can harden (like papermache) and stop water from getting to soil | |
| Biodegradable | ||
| Old clothes and rags | Cheap | Slow to break down |
| Recycling | Untidy | |
| Biodegradable | ||
| Pea Straw | Contains valuable nutrients (high in Nitrogen) | Expensive |
| Retains water | ||
| Biodegradable | ||
| Looks good | ||
| Pine Needles | Controls weeds | Slightly acidic (negligable) |
| Breaks down slowly | Difficult to get in some areas | |
| Doesn't attract termites | ||
| No tree harvesting used | ||
| Allows all moisture to get down into the soil beneath | ||
| Looks good and smells nice | ||
| Sawdust | Excellent snail and slug deterrent | Can cause breathing difficulties when laying it |
| Timber may have been treated | Can come from non-sustainable processes | |
| Biodegradable | Sucks up the nitrogen from the soil as it breaks down | |
| Seaweed | High in nutrients | Smells |
| Controls weeds | Need to wash it beforehand to get rid of salt | |
| Biodegradable | ||
| Stones | Looks good | Doesn't break down |
| Excellent drainage | Hard to keep neat when leaves, etc. fall on them | |
| Allows all moisture to get down into the soil beneath | Can be expensive | |
| Insulation protects soil from extreme temperature fluctuations | Good gliding surfaces for snails and slugs | |
| No nutrients | ||
| Straw | Popular on paths - provides traction if icy conditions | Wet straw attracts slugs |
| Can hold pesticides | ||
| Has been linked to Aspergillosis (fungal infection) in birds | ||
| Sugar Cane Mulch | Contains helpful nutrients | Can hold pesticides (choose organic) |
| Clumps together so good for sloped land | ||
| Easy to use | ||
| Reasonable cost | ||
| Biodegradable | ||
| Tea Tree Mulch | Smells nice | Expensive |
| Looks good | ||
| Great for native trees | ||
| Biodegradable | ||
| Weed Mats | Controls weeds | Dangerous to birds - getting pieces caught around legs which either cut off circulation or cause bird to be trapped in a trees (usually hanging upside down by one leg) |
| Non-biodegradable | ||
| Wood Chips | Look good | Expensive |
| Biodegradable | Can come from non-sustainable timber production | |
| Can come from treated timber |
I hope this table helps to answer your question, Linda. Each has good and bad characteristics. According to your budget and land size choose what works best for you. A retired couple I know who have their ‘vegetable patch’ in pots on a patio use stones as mulch, quite successfully. They add nutrients in the form of liquid fertilizer from their worm farm. Stones, however wouldn’t be economical or provide nutritional value to plants in a large vegetable garden.
Being on an average sized alotment we use live mulch (in the form of Companion Plants – lots of them!) and Sugar Cane Mulch for my Vegetable Garden and Orchard. But my biggest fear now is that LTSH will want to ’split-test’ mulches and graph the outcomes…
sigh…
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About the Author: 
Scott Jacobs | Nov 23, 2008 | Reply
Although I definitely have a vested interest in selling pine needles/pine straw, I did want to give you some additional information on it for your chart besides the fact that it controls weeds and is acidic. On our website, there is a list of lots of other positive properties of pine straw. That pine straw is highly acidic and only acid loving plants can be grown in it is mostly a myth. Pine straw in itself is slightly acidic. As it naturally breaks down, it becomes even less acidic. For it to lower your soil’s pH even a little, takes many years, and even then, the decrease is only very slight. Most any plant that can be grown with other mulches can be grown with pinestraw as a mulch. I would like to either link to your table or use it on my site and giving you or your site credit in the future if it gets some updates to the pine straw section. Very nicely done chart by the way!
admin | Dec 4, 2008 | Reply
Hi Scott – Thank you for your comment and for educating us on Pine Straw. I’ve updated the table. For anyone else reading this, if you would like to find out more advantages of Pine Straw please check out:
http://www.pinestrawdirect.com/