Growth in gardening: Mulching Magic

As the days of June get warmer I am reminded that summer’s “serious heat” is just around the corner. Every year about this time I get folks asking for advice on preparing their garden and flower beds to handle the heat. My answer is to employ the magic of mulch.

Mulching is the practice of covering the soil around the plants you want to grow. This is done to boost the various natural processes that help growth and to suppress weeds. It’s something that nearly all organic textbooks recommend and is amazingly easy to incorporate into any garden system.

Adding mulch is one of the best things you can do for your garden. When used properly, mulch will help soil retain moisture and an even temperature, suppresses weeds, encourages worm and microbial activity, prevents erosion and adds organic matter to soil. What’s not to like?

As much as I love the practice of mulching, there are both pros and cons the home gardener needs to be aware of. Wow, I feel almost like an “organic heretic” just thinking about saying anything negative about mulch, but here goes…

First off, we need to understand that mulching can be done in several ways: organic and inorganic. While there are several types of landscaping mulch available, each with its own pros and cons, they all fall into one of those two categories. There is a difference in the two types of mulches. Inorganic mulches do not decompose, so they do not get absorbed into the ground. Inorganic mulches include such things as plastic, gravel, shredded rubber and landscape fabric. Organic mulches, on the other hand, will break down over time, which adds nutrients and texture to the soil. Organic mulches include such things as bark or hardwood, woodchips, straw, newspaper, sawdust, pine needles and grass clippings.

Let’s look at some of the most common types of organic and inorganic mulches that are readily available to the home gardener and evaluate a few pros and cons with each type of mulch.

Shredded Hardwood Bark Mulch:

Shredded hardwood bark mulch is made from pure tree bark and not ground up wood.

Pros: It contains a lot of nutrients that will improve the soil as it decomposes.

Cons: Wood chips may wash away as the wood decomposes, and they pull some nitrogen from the soil.

Grass Clippings Mulch:

Grass clippings mulch should be used after they are dried and spread in thin layers to prevent them from rotting.

Pros: Grass clippings are free from your lawn and supply compulsory nitrogen nutrients to the soil. If you do not use lawn chemicals, it is also organic.

Cons: It is often difficult to separate the grass from the weeds, which can increase weed growth in the garden.

Straw Mulch

Straw mulch has become increasingly more popular over the last several years.

Pros: Straw is inexpensive, provides good insulation for a winter vegetable garden and suppresses weeds.

Cons: Straw decomposes quickly, can be unattractive, may contain weed seeds and is flammable.

Rock, Gravel, Stone & Lava Rock Mulch

Rock, gravel, stone and lava rock mulch materials do not break down. If this type of mulch is properly installed, it may never need to be replaced.

Pros: It is available in a wide range of colors, sizes and shapes. It will not decay or blow away.

Cons: These can be difficult to keep clean and difficult to remove. Rocks draw heat and should not be used with acid-loving plants, such as rhododendrons. Must use fabric under the rocks to prevent them from sinking in the soil.

Shredded Rubber Mulch

Shredded rubber mulch offers the benefit of using recycled rubber as a mulch so that you will be preventing the material from ending up in a landfill.

Pros: Available in several different colors and it will not blow away or decompose.

Cons: It is often difficult to remove, it is inorganic and is flammable.

Plastic Mulch

Plastic mulch is typically sold in sheets that are placed directly over the soil. In most situations, a layer of another type of landscaping mulch is placed over or mixed with the plastic.

Pros: It is very effective at controlling weeds and absorbs heat, making it especially useful in gardens where warm soil is desired.

Cons: Soil cannot breathe under the plastic. It’s also inorganic, unattractive and may tear easily.

When choosing landscaping mulch, it is best to research the type you are considering ensuring it is appropriate for the area where you want to install it. For example, if you want an attractive mulch in a flower bed that is in front of a business, rock or gravel may be the most appropriate, because it is both attractive and low maintenance.

In my own yard and garden, I go with organic mulches, mainly wood chips, grass clippings, leaves, and cardboard. I recommend mulching 100 percent and truly believe it is among the best ways to combat our hot summer months.

That having been clearly stated, and without wanting to be denounced as an “anti-mulchite,” I must point out a few more cons. First, a too thick layers of mulch can absorb light rains – and water from sprinklers – and stop it from getting through to the soil. Secondly, mulch can keep soil too cool in spring, when you want it to warm up. Thirdly, with woody mulches there’s a phenomenon called nitrogen drawdown, caused by microorganisms drawing nutrients out of the soil to break down mulch above. A layer of compost or a sprinkling of blood and bone meal beneath the mulch can help counteract this. Finally, mulches can attract slugs, snails, mice and other unwelcome guests to the garden.

My hands down favorite mulch is cedar mulch. It offers an excellent option when it comes to perennial flower beds and other landscape gardens.

Cedar mulch, as well as other bark and wood mulches, are quite long lasting and break down over time to provide added nutrients to the soil. Cedar mulches also discourage insects from taking up residence in the garden, thus making the use of insecticides unnecessary. It is also readily available in most nurseries and garden centers and presents an organic and cost-effective option for mulches.

Although cedar mulch breaks down and is organic, it takes longer to break down than alternative bark mulches or wood mulches. Because of this, cedar isn’t as effective in returning nutrients to the soil as some other forms of mulch. Cedar mulch does discourage insects from moving in, but it must be remembered that not all insects are harmful. Cedar mulch may discourage beneficial insects as well as traditional pests from entering the garden.

Whichever way you choose to mulch, just do it. The positive benefits absolutely outweigh the negative, so get out there and mulch away.

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Joe Urbach is the publisher of GardeningAustin.com and the Phytonutrient Blog. He has lived in the Central Texas area for over 30 years. Urbach is a certified Texas Master Gardener from Hays County and is currently serving as the director of training. For more information on the Master Gardener program contact the Hays County AgiLife Extension Service at 512-393-2120.