Mulching is the act of applying a layer of material, usually natural, on the ground surface, around growing plants. It prevents the growth of weeds and the loss of moisture. Average thickness is 5-7cm of mulch. It encourages the activity of earthworms and keeps the soil from becoming hard. In the long term it breaks down and forms humus and nutrients.
Closely related to mulch is the use of cover crops, i.e. crops that grow relatively close to the ground and prevent weeds emerging.
Benefits[edit | edit source]
Mulch offers many benefits:
- Greatly reduces weed growth, and makes weeds much easier to pull out with their root systems.
- Prevents erosion.
- Retains moisture.
- Prevents a hard surface forming on the soil, allowing it to more effectively exchange oxygen and carbon dioxide and absorb water.
- Organic mulch breaks down and provides nutrients and organic matter to the soil, and encourages activity by earthworms and other helpful organisms.
- Dark mulch absorbs warmth from the sun, helping to warm the soil in child climates and after winter. (Dark plastic is most effective for this purpose as it is thin and transmits the heat easily to the soil, and quite effectively traps the heat.
Methods[edit | edit source]
With mulching, organic matter is applied in thin layers between the plants. The application of a mulch layer can only happen when the seedlings have grown well above the soil or if the plants are planted. Sowing or planting in a mulch layer is an inefficient task. Do not apply the mulch layer near frost sensitive plants before half May. By covering the soil, it will not be able to radiate heat at cold nights, so the danger of frost damage is then greater.
Very thick mulch can be very effective, without harming the plants.[verification needed] deep enough that you have to dig a bit to find what's underneath, e.g. 10cm/4in or more.
Mulching also poses some dangers as it also closes off the soil, so the temperature is lower at night; more risk of nighttime frost (temperate climate countries).[verification needed]
Weeds have to fight to get through such thick mulch, and often fail. If they do make it through, they can be easily pulled out of the loose, moist soil that develops beneath the mulch.
Pull out big weeds before mulching. Or, for a lazy gardening approach, try tramping them down - this assumes you're ok with coming back to pull them out later, if they don't stay stay down - but the soil should have softened and it will usually be much easier.
Weed inhibiting crops cover the soil off completely or are spaced so far apart that we can properly hoe between it. Weed promoters do not have these qualities (eg garlic and chive).[clarification needed]
We can use Organic mulch:
Lay down at least 5” thick of mulch that does not have weed seeds in it such as straw. Mulch can be put around transplants or over plants like garlic, onions, and potatoes.
We can also use Plastic mulch:
Lay down plastic and plant in poked holes. Some problems are that plastic breaks down quickly, makes a lot of trash, and blocks water.
We can plant a cover crop: Plant a cover crop that out grows the weeds, such as summer buck wheat and vetch or winter oats, bell beans, and vetch.
Finally we can have parts of the field (between crops) irrigated poorly For areas with long dry seasons bury your drip irrigation tape and irrigate only where needed.
Types of mulch[edit | edit source]
Many materials can be used as mulch, including:
- Bark (but beware of problems with fungus - see below).
- Leaves. These break down quickly and improve the soil.
- Straw. Be particularly aware of seeds in the straw, as the straw is likely to have been cut after the grass or other plants have gone to seed. They will probably be easy to pull, but if left they can become established and hard work to pull out.
- Shell grit
- Plastic. This offers most of the benefits of organic mulch (protects from weeds, prevents erosion and retains moisture) and it also helps to trap the sun's warmth. However, it adds no organic matter or other nutrients to the soil.
- Red plastic mulch reflects certain wavelengths of light back into the plants, especially those that encourage fruiting and the ripening of fruit.
- Lucerne hay. This contains a good amount of nitrogen, along with trace elements. It can be a good addition to an infertile soil or when establishing a garden.
- Meadow hay. This contains weed seeds though, so isn't always a good choice.
- Seaweed. This is suitable for gradual breakdown and slow release of trace elements. Otherwise, it can be too slow to break down for many garden uses.
- Cardboard. Often free or very cheaply available and breaks down quickly. There may be problems with contamination.
Cautions[edit | edit source]
- Mulch containing seeds, such as lawn clippings when the grass is seeding, or straw, can result in an increased number of weeds. Ways of dealing with this are:
- When mowing, or growing a crop for mulch, cut it before the seeds approach maturity.
- Have an additional thick layer of seed-free mulch on top.
- Be sure to pull out the weeds before they become too established, while it is still extremely easy.
- Compost the mulch before adding it to the garden. Form the mulch into a pile, wet it or let it soak up rain, and let it sit for a few months. Moisture in the pile will germinate the seeds. Turning the compost every few weeks will bury any germinated seedlings on the top deeper into the pile, where they will die and decay. Decay heat will build up in the interior of the pile, cooking seeds and killing them.
- Cocao mulch can be harmful to dogs (if they eat it - and not all dogs eat it).
- Your Best - and Worst - Mulching Options WTOPnews.com claims that rubber tires are bad, and wood and bark mulches promote certain fungi that cause damage and nuisance, and should be kept approx 10m/30ft from houses and cars.
- Avoid mulch made from old roofing shingles.
- Some advise keeping mulch away from the foundation of buildings, to avoid pests. (It might be expect to affect rising damp as well, if the building is prone to that.[verification needed])
- This list should be added to. Do a google search ignoring the main warnings mentioned above, and of course read critically.
Note that an email warning about termites in mulch in 2006 was dismissed as a hoax
Notes and references[edit | edit source]
- Shell grit as much
- Review: red plastic mulch for tomatoes – does it make a difference?
Is There A Difference In Red Mulch? — Plasticulture — Penn State Extension, Department of Horticulture, Pennsylvania State University
- Cocoa Mulch, Snopes Urban Legends Reference Pages and Cocoa Mulch Toxic to Dogs Warning Email hoax-slayer.com.
- (Oregon) State issues warning about mulch made from old roofing shingles
- Formosan Termites, Snopes.com and Formosan Termites in Mulch Warning, hoax-slayer.com
See also[edit | edit source]
[edit | edit source]
- Wikipedia:Sheet mulching
- Guide to Selecting a Garden Mulch | Tips & Techniques - GardenGuides.com, includes information on a large number of different organic and inorganic mulches.
- Mulching - NRCS - public domain, planned for porting.
- Mulch Clemson University - Clemson Extension, Home & Garden Information Center