A thick cover of mulch protects the soil, prevents weeds from growing and provides food for beneficial creatures in the soil. If you know the properties of the different materials, you can use them in a targeted manner.
Covering the soil with leaves or shredded material improves soil quality, protects the delicate fine roots of shrubs from direct sun, suppresses weeds and increases soil moisture: here are 10 tips for the proper use of mulch.
In a nutshell: How to mulch properly?
The biggest mistakes in mulching are made in the choice of material, the thickness at which it is spread, and by not applying nitrogen fertilizer when using bark mulch, for example. You mulch properly if:
- You apply organic nitrogen fertilizer to the soil before spreading bark mulch or wood chips.
- You apply lawn clippings preferably dry and no more than two centimeters (1 in) thick.
- You spread bark mulch to inhibit weed growth at least five centimeters (2 in) thick in beds where no herbaceous young plants are growing.
What does “mulch” mean?
Mulch usually refers to a soil cover made of natural, easily decomposable, organic materials. Depending on the material, the layer, which may be more or less thick, protects the soil from the effects of weather such as frost, wind and rain, prevents water stored in the soil from evaporating too quickly in summer and regulates undesirable wild weeds. In practice, this means less watering, hoeing and weeding. And just like on a compost pile, the material is gradually transformed into fertile humus by soil organisms. This makes mulching an important measure for building up humus in the garden. Only those who prefer to use fleece or foil do without this important effect.
Mulching with foil, fleece and paper
The advantages and disadvantages of ribbon fabric or fleece made of dark plastic fibers balance each other out. Under them, the soil warms up quickly, remains moist for a long time, and even areas colonized by root weeds can be rehabilitated. However, the first few centimeters/inches of the soil surface are really heated up and aeration is restricted. Biodegradable films made of paper or corn starch decompose within a few months, so they are only recommended for short-term use, for example, for beds with cucumbers, pumpkins and other vegetables that require warm, but at the same time quite moist soil.
Bark mulch and bark humus
Bark residues come from forestry or sawmills. Products made from medium coarsely ground pine, Douglas fir or spruce bark are most effective in suppressing budding weeds. Use it to mulch newly planted perennial beds, paths and ornamental shrubs. For long-term protection, a layer thickness of 7 to 10 centimeters (3 to 4 in) is required. Carefully remove root weeds such as goutweed or couch grass beforehand, otherwise they will soon grow through the mulch cover. Vegetables and herbs do not tolerate bark products, also mulch roses with fermented bark humus at best.
Fresh wood chips for woody plants
Even a simple garden shredder can be used to make good use of regularly occurring wood cuttings. Because fresh wood consists mainly of lignin, it decomposes very slowly. This is why the material is used as permanent mulch under ornamental shrubs. Important: Above all, do not apply finer chaff, as produced by most devices for hobby gardeners, too thickly, otherwise the air circulation in the root area will be restricted too much and the woody plants will care.
How to dispose of lawn cuttings?
Fresh lawn cuttings or grass clippings usually accumulate in abundance in the summer. The stalks provide plenty of nitrogen. Because the clippings are very moist, the layer thickens within a few days. On sunny days, the surface dries out and becomes crusty, and rot develops underneath. Therefore, spread fresh material only very thinly and renew it weekly. For a thicker layer, allow the mown material to wilt for a few days, loosening or turning it several times. Do not reapply until the previously applied layer has collapsed.
Straw protects against fungus and secures the harvest
A bed cover made of coarsely chopped straw has proven especially useful for growing strawberries. The fruits remain clean as well as dry and are less affected by gray mold or rot fungi. The straw should only be applied after the soil has warmed up or during the main flowering period. A small bale (10 to 15 kilograms / 20 to 30 lbs) is sufficient for an area of about 100 square meters / 1,100 square feet.
Mature compost – not only for roses
Mature compost can be used to cover seed furrows and planting pits, where it specifically promotes seed germination and rooting of young vegetable seedlings, fruit trees and other young plants. To improve the soil structure when planting new beds, the compost layer can be several centimeters high. Rule of thumb: To cover a square meter of area about one centimeter high, fill a bucket with a capacity of ten liters. Five liters are sufficient for mounding the sensitive grafting site of freshly planted roses.
Coconut mats as a protective cover
Whether used as winter protection mats to protect against ice and frost or to prevent the upper soil layers from drying out due to wind and sun, all plants benefit from the air-permeable bed cover, especially shallow-rooted plants such as blueberries and cranberries, kiwis or elderberries, but also ornamental plants such as woodbine and honeysuckle. The three to five centimeter (1 to 2 in) thick mats are made from the edge layers of the coconut, with organic natural rubber serving as the binding material. A pair of garden shears is all that is needed to adjust the width and length or cut out planting holes. Alternatively, there are round mulch discs, already slotted, which are placed around the trunk or the base of the bush like a collar. Shelf life of coconut products: two to three years, after which rake and compost the remains.
Mulch with leaves – it’s all in the mix
As in nature, you can simply leave autumn leaves under ornamental and fruit trees and shrubs; provided that the trees and shrubs were free of pests, fungal infestations or other easily transmissible plant diseases. Oak, walnut or chestnut leaves contain abundant tannic acid. Unmixed, you can use previously chopped leaves as mulch for bog plants such as azaleas or hydrangeas. For other plants, it should be shredded before use along with “neutral” garden waste such as grass or crop residues.
Balancing mulch and fertilization
Green mulch materials supply the soil with all important nutrients, and additional fertilization is usually unnecessary. However, straw, bark mulch and wood chips remove nitrogen from the soil as they decompose. To avoid disturbing plant growth, rake horn shavings into the soil before spreading. Permanent mulch, as in the bed with blueberries or rhododendrons, push aside in spring, apply acidic special fertilizer, cover the soil again and supplement the mulch layer if necessary.