Mulch Types for Flowerbeds

Mulches to Improve Your Flower Garden

Gardener Spreading Mulch in Garden, Toronto, Ontario, Canada
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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.

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. Inorganic mulch examples include plastic, rocks, or aluminum foil.

The Dyed Mulch Choice

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.

Rocks as Flowerbed Mulch

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.

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.

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.

Landscape Fabric Pros and Cons

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.

Living Mulch Pays it Forward

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.

Mulch and Soil pH

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 allow most flowering plants to thrive.

Can I Mulch With This?

Here is a list of 25 organic and inorganic mulches to experiment with in flowerbeds. Not all mulches will be available in your area; check your region for sawmills or food processing centers for waste products. 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.
  • Bark nuggets are ornamental and long lasting. 
  • Black plastic is excellent for smothering stubborn weeds in new gardens.
  • 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. 
  • Compost is a great choice for any flowers that need a nutrient boost.
  • Cornstalks work well mixed with other materials for a no-till garden.
  • Grass clippings should be dried out before application to prevent odors.
  • Ground corncobs won't blow away, and enrich the soil with nitrogen.
  • Landscape fabric must be maintained annually to prevent weeds from anchoring it to the soil.
  • Lava rocks are ideal for rock gardens.
  • Leaves improve soil tilth, especially when chopped.
  • Newspaper works well on paths; top with wood chips.
  • Pine needles won't become compacted, and slightly acidify the soil. 
  • 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. 
  • Sawdust is fine if you don't mix it into the soil. 
  • 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. 
  • Stones are fine for rock gardens, but avoid limestone to prevent pH changes. 
  • Wood chips are inexpensive, widely available, and suitable for most gardens.