An Introduction To Organic Mulches
Gardeners are very fond of using mulch for a few reasons:
- It helps prevent weed growth by forming a barrier over the soil, this makes it more difficult for seeds to germinate.
- Helps control the soil temperature (especially useful in hot summer weather).
- Helps retain soil moisture by reducing the amount of evaporation.
- Helps protect plants over winter (from freezing/thawing/heaving soil).
Organic mulches not only do all of the above, but they also help enrich the soil with nutrients as they break down. The added bonus is that cost is minimal since you’re repurposing materials…many that nature readily provides.
Here’s a list of items you can use and a general introduction to each. I’ve also added several sources at the bottom of this page so you can gain more in-depth knowledge about everything “Mulch”.
- Wood Chips: One of the best performers in terms of moisture retention, temperature moderation, weed control and sustainability (pdf source). There is a lot of information provided in the pdf I linked to (including addressing common concerns…in a nutshell: they’re much ado about nothing). Takes longer to break down but you can shred it finer to help it decompose quicker.
- Grass Clippings: Avoid applying any thicker than 2″ since it can form a mat and start repelling water when it’s too thick. Breaks down quickly which benefits the soil though you can mix it with peat moss if you want it to slow down a bit. May contain weed seeds. For best results, allow to dry out for a few days first. If using around food plants, don’t apply any clippings from a lawn that was treated with chemicals.
- Hay/Straw: Excellent to use as winter protection (for bulbs, strawberries, perennials) though can be a haven for rodents if piled too thickly. Straw is a good choice for using around strawberries in the summer, they seem to love it. Semi-rotted considered best. May contain seeds.
- Leaves: Shred or allow to partially rot first before applying (in Spring/Summer) since whole leaves can mat together and form a water/oxygen barrier. Fine to use whole leaves for over-winter applications. They contribute humus, nitrogen and other nutrients to the soil as they break down.
- Manure: Only use when well rotted. High-Nitrogen Recipe: Layer fresh horse manure with old, partially rotted alfalfa hay. Leave it alone until it turns a dark brown (will take a few months), no tossing necessary. From The Magic of Manure.
- Compost: Only use mature compost, this is an excellent source of nutrients, attracts earthworms and is a warrior for disease control.
- Plant Debris: A good over-winter mulch that nature itself uses, gather up all plant refuse (leaves, twigs, garden growth) at the end of the season and shred it all up together. Rake up any remains in the Spring so the soil can warm up and get ready for planting.
- Newspapers: Either shred or lay in sheets (at least 6 pages thick), spray with water then cover with a thin layer of organic material (pine needles, compost, manure, etc.) to help hold the paper in place. Will break down quickly adding organic matter to the soil.
- Pine Needles: Thought to make soil more acidic so only use this around plants that will love it (blueberries, hydrangeas, etc.). Will take awhile to break down. Good to use over winter.
- Sawdust: As with pine needles, use around acid-loving plants.
Mineral Mulch: If you’re looking for something that will serve its purpose for a long time and is fairly hands-free, gravel and pebbles are a good option. They’re decorative, won’t break down (though they can settle in the soil) and won’t be tossed around on windy days. They can be helpful in cooler zones since it will help keep the soil warmer longer.
How to apply:
- Clean area of all weeds.
- Apply in mid to late Spring when the soil has thawed and is starting to warm up. Watch you don’t cover new seedling growth. Apply again in the Fall for overwintering, if there is still a layer of mulch on the ground, dig it into the soil (turn it over) and apply a fresh layer.
- Depending on what you are using, layer the material evenly 2″ to 4″ deep (4″ to 6″ deep for winterization).
- Pull away any material touching plant stems so it doesn’t cause them to rot or create a disease friendly environment (space about 2″ or so).
- Top up as needed as the material slowly incorporates itself into the soil.
- If you want to speed up the decay process, chop or shred materials first and mix with compost or well-rotted manure.
The above list is not exhaustive and there are plenty more items you can use. I found a lot of great information from the sites listed below if you’re interested in further reading: