If you follow the gardener’s adage of spending nine dollars of your ten-dollar gardening budget on the hole, and one dollar on the plant, part of that nine dollars needs to be allocated towards mulch. With so many colors, textures, and materials to choose from, flower gardeners need to invest carefully in this soil-building essential.
The Best Mulch for Flowerbeds
The best mulch is the one you are willing to maintain. Some gardeners swear by compost or manure for their enriching properties; others demand specialty mulches like cocoa bean hulls for their ornamental value. Experiment and invest in the one that suits your landscape and climate.
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Compost
Compost is organic material in various stages of decomposition. Mature compost is dark brown and crumbly with soil-like particles, and it has an earthy smell. Applying a thick layer of compost over soil around your garden ornamentals helps to suppress weeds like most mulches but it also leaches nutrients constantly into the soil whenever it rains or you irrigate your plants. The compost will slowly work down into the soil and need to be refreshed over the growing season.
Mushroom compost is a substrate that is specially blended and used by the mushroom growing industry, then, when spent, is bagged for use as a soil conditioner. Used fresh, it is a good mulch option because it’s harder for weed seeds to take root in it. It also will eventually break down into the soil.
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Organic or Inorganic Mulch?
In reference to mulch, organic doesn’t mean the absence of chemicals. Organic mulches are derived from living things, such as shredded bark, grass clippings, leaves, and even paper. Shredded bark from native trees is always better than other wood-based mulch options. Organic mulches will eventually break down and need to be refreshed. Inorganic mulch examples include rubber, plastic, rocks, or even aluminum foil. These materials will not decompose into the soil.
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Dyed Mulch
Red, brown, and black dyed mulches are showing up in landscapes everywhere. The product is usually waste wood (like shipping pallets) ground up and sprayed with a variety of dyes. The mulch is 20-40% more expensive than traditional mulch, and the vivid color may steal the show from your flowers. The color will fade over time, making the landscape seem reminiscent of a down-at-the-heels office park. However, some gardeners like the aesthetics of dyed mulch, and the fad continues.
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Rocks
There are pros and cons to rock mulches. Rocks don’t break down, and therefore provide a semi-permanent mulch (even rocks get dispersed over time). Rocks won’t improve your soil and may look untidy when dead plant material accumulates on them. Reserve rock mulches for alpine flowers, which thrive in rocky sites in nature.
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Rubber Mulch
If you’re worried that your mammoth sunflowers or hollyhocks might fall and hurt themselves, use rubber mulch. Otherwise, save this product for playground areas, or if you crave the cushioned feeling underfoot, use it on your garden paths. Rubber mulch does nothing to amend the soil, and the pieces have an unpleasant way of migrating all over the landscape, creating a debris field that never goes away.
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Sawdust or Fresh Wood Chip Mulch
Horticulturists warn of the dangers of fresh wood chips robbing nitrogen from the soil as the wood decomposes. Fresh chips are safe to use as mulch, as long as they aren’t mixed into the soil. Finely ground sawdust can mat in the rain or blow away in dry weather and may make a better mulch when blended with straw or shredded bark.
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Landscape Fabric
Properly maintained, there’s nothing wrong with landscape fabric in the flower garden. However, gardeners try to camouflage it with wood chips, and the chips will eventually break down. Then, weed seeds can germinate on top of the fabric, creating an unholy mess that’s nothing like the maintenance-free garden the gardener intended when he installed the fabric.
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Living Mulch
A living mulch is another term for cover crops, most common in agriculture. Plants like clover, buckwheat, annual rye, or alfalfa are grown in an empty garden bed and then tilled into the soil for enrichment. Also known as green manures, these crops are usually used in fallow vegetable beds. Flower gardeners preparing a new bed may find a living mulch useful to prevent erosion and add organic matter to the soil before planting the flowers.
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Pine Straw Mulch (Pine Needles)
Pine straw mulch is made from fallen pine needles. After the pine needles have dried, they become pine straw. Pine straw can be used as a yard or garden mulch, much like wood mulch, straw, or shredded leaves. Gardeners with camellia or azalea plants may seek out pine needles to help acidify the soil. In fact, any organic mulch will slightly increase soil acidity as it breaks down, including shredded leaves and compost. Aged pine needles average 6.0 pH, a slightly acidic pH that allows most flowering plants to thrive.
Pine straw mulch offers additional advantages, such as being dense yet porous, attractive, stable, and low-cost or even free.
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Straw Mulch
Straw mulch is a by-product of grain plants; rye, barley, oats, rice, and wheat.1 Threshing removes the grain and chaff, and stalks are baled and sold as mulch, animal bedding, and for other purposes.
Straw mulch is added to lawns, vegetable gardens, and small fruits. Its messy appearance doesn't offer an aesthetic appeal in ornamental flower beds, so landscaping use is limited. It is, though, an efficient insulator for winter protection—it breaks down rapidly and enriches soils, which makes it ideal for edible gardens.
Can I Mulch With This?
Here are additional organic and inorganic mulches to experiment with in flowerbeds. Save the most expensive mulches on this list for your containers or the front of the border of your flowerbeds:
- Alfalfa hay adds nitrogen to the soil; you can use freshly chopped alfalfa that hasn't gone to seed.
- Aluminum foil may repel slugs and aphids and reflects light onto plants.
- Buckwheat hulls have an attractive dark brown color and fine texture.
- Burlap should be 100% natural jute so it can break down in the soil.
- Cardboard can be covered with a thin layer of bark chips to disguise it.
- Cocoa bean hulls smell great and add an attractive reddish-brown hue.
- Coffee grounds may be free at your local cafe. Grass clippings should be dried out before application applying to prevent odors.
- Ground corncobs won't blow away and enrich the soil with nitrogen.
- Lava rocks are ideal for rock gardens.
- Newspaper works well on paths; top with wood chips.
- Rice hulls aren't widely available; use this lightweight material in containers.
- Salt hay doesn't carry weed seeds, as material comes from saline marshes.
- Seaweed (rinsed with fresh water) doesn't need to be composted; add straight to flowerbeds.
- Sphagnum moss is expensive and works best in small containers.
Worst Types of Mulch for Flowerbeds
Avoid these types of mulches in your ornamental beds and borders:
- Artificial turf
- Plastic weed block
- Gravel or crushed rock
- Wood chips made from old pallets
- Rubber mulches made from ground tires