Flowerbed Mulching 101

Mulching Basics for Flowerbeds

Using spade to apply loose mulch around Erica carnea in flowerbed
Dorling Kindersley/Dorling Kindersley/Getty Images

Flower gardeners know that soil, fertilizer, and water are important elements of a healthy flower garden. The proper use of mulch helps all three of these garden elements work the hardest for you.

Why Use Mulch?

Mulch helps to keep soil and roots cool, which is especially important for young plants struggling to become established in hot weather. Part of the way it does this is by retaining soil moisture.

Mulch can prevent weeds, both by denying the sunlight that triggers germination of seeds, and by acting as a physical barrier between seeds and the soil. And, unlike artificial landscape fabric, it fertilizes the soil (in the case of organic mulches like compost, manure, grass clippings, and aged wood chips). Furthermore, mulch encourages earthworms, which come to the soil surface in the evening to feed on decomposing organic matter.

Mulch keeps plants pretty by preventing soil from splashing on leaves, which can stop the spread of soil-borne diseases. Mulch itself adds a decorative element to the landscape, providing a sense of unity between flowerbeds.

What Kind of Soils Benefit From Mulch?

Both sandy and clay soils need mulch in the flower garden. Mulch helps sandy soils retain the moisture that drains quickly away, and clay soils get the benefits of aeration from increased earthworm activity. Every soil type receives beneficial nutrients as organic mulches break down.

Organic vs Inorganic Mulch

Organic mulch does not refer to the presence of chemicals in mulch; rather, it refers to mulch made from carbon-containing materials that were once living. Wood chips and compost are two of the most popular organic mulches sold in home improvement stores. Gardeners can make their own mulch by raking up pine straw, making leaf mold, or composting garden waste and kitchen scraps at home. Organic mulch will acidify soil as it breaks down, and will improve soil tilth.

Inorganic mulches include non-carbon containing soil covers like rocks and rubber playground mulch. Rock mulch like gravel or lava rock is an excellent choice for alpine garden plants that need sharp drainage and thrive in lean soil. In this case, rock mulches function to keep loose soil from washing away in a heavy rain, and also add a sense of definition to the flowerbed.

Rubber mulch is usually reserved for playground surfaces, where the elastic properties protect children from falls. Rubber mulch does suppress weeds and retain soil moisture, but it does not enrich the soil and can migrate into the yard, getting caught in the mower.

About Dyed Mulch

As hardwood mulch ages, it weathers to a natural grey color, losing the vibrant golden brown that pops against green foliage and colorful flowers. An antidote to this fading is the use of dyed red or black garden mulch, but is it safe? Carbon-based dyes produce black mulch, and iron-oxide dyes produce red mulch. Neither are considered harmful for the soil. The sources of the hardwood themselves, such as wood treated with arsenic-based wood preservatives, are usually more of a concern than the dyes used to color the wood. Cocoa bean mulch is one alternative that holds its natural reddish-brown hue.

Determine How Much Mulch Your Garden Needs

Gardeners should strive to keep one to four inches of mulch on their flowerbeds. More than four inches of mulch can cause problems like fungal diseases. Whether you use one or four inches depends on the type and size of the mulch particles: use less mulch if you’re using sawdust; use more mulch if you’re using straw. Apply these calculations to estimate how much mulch to buy.

Mulch Is not a One and Done Activity

Don’t be the gardener who applies mulch one time, and never does again. Small mulch particles break down quickly in hot or wet weather, and you may need to add mulch more than once in the growing season to maintain a functional layer. Large mulch particles, like pine nugget bark, break down slowly and may only need refreshing once every two to three years.

When to Apply Mulch

You can apply mulch whenever the soil is bare. In the spring, mulch suppresses weeds. In the summer, plants appreciate protection from scorching temperatures. In the fall, gardeners take advantage of the bounty of fallen leaves to renew their mulches and amend the soil. Even the winter garden needs mulch, as it prevents frost heaving of plants.

Save Money on Mulch

Check your local utility company for a truckload of free tree trimming remnants. Newspaper and cardboard also make a fine mulch base, which you can cover with prettier materials. Serious gardeners have even been known to muck stables, root through coffee shop dumpsters for grounds, or scour neighborhood curbs for leaf bags in order to feed hungry flower gardens.

Should I use mulch in my flowering containers?

Yes! Mulch provides all of the same benefits to container flower gardens that it provides to plants in the ground. Flowers in containers are particularly susceptible to drying out, especially those in terra cotta pots, and mulch helps to prevent this. Since flowerpots are subject to closer scrutiny than plants in the ground, consider investing in a premium mulch that has a high aesthetic quality. Sphagnum moss, pottery shards, or common glass marbles are three attractive options. Decorative seashells are fun to use in a container garden by the lake, pool, or ocean.