Using glass mulch in the landscape
Story by Margo L. Emery, Ph.D.
I first encountered the magical material known as glass mulch at the University of Tennessee Gardens, Crossville. My body froze as my eyes took in a large, neat bed of shiny, multicolored … something. Meanwhile, my brain was clamoring to know what it was and – just as urgently – where I could get some. That pretty much captures how many gardeners react when they come across this sparkly stuff. The glass can appear so otherworldly; it is perfectly reasonable to wonder if unicorns are involved.
While gardeners are quick to view the glass pieces as mulch, the terms used by the processing centers that produce them are chips, jellybeans or jelly stones. They are the output from crushing the bottles we place in our recycling bins and represent the final stage of processing before many recycling centers haul glass to a landfill. Yet, a growing trend is to find alternative uses for this resource. These include grading roads, as foundations for concrete pads, and even to form decorative countertops.
If you’re reading this and envisioning sharp glass shards, well that has changed. Some processors are adding equipment that tumbles and polishes the pieces. Run them through your fingers, and they’re as silky as beach glass, but with a shine to rival any diamond Tiffany cares to display in its windows. These are the recycling centers to seek. They may sell the material at a low cost for you to haul away. Others, such as the processor in Crossville, now offer chips free to community members.
Many large urban recycling centers have partnerships for their glass output. While you may get lucky finding free or low-cost glass chips, chances are greater at processors in smaller communities due to their lower volume of output. City and county public works departments can provide you with information about their processors and help you reach them. Ask if glass chips are available, their cost, size, and available colors. Most likely you’ll find the bottle colors mixed together. If a center does not offer polished chips, it may know of another that does.
Glass chips can also be purchased from retailers and by special order from Internet sources. The plus here is that single colors are available. The downside for special orders is the high cost of shipping heavy material.
The first thing to know is that glass mulch gets hot in the sun. So, if you’re using it around plants, opt for heat-tolerant, less water dependent ones – such as marigolds (Tagetes spp.), Petunia, and Lantana. Even so, keep an eye on their moisture during hot, dry periods. Yucca is a good choice, as are cacti and succulents.
If you’re a shade gardener, glass mulch just may become your new best friend. It adds light to dark areas, gleam to a bed’s surface, and pops of shine where needed.
Containers beg for mulch, especially dish gardens. Indoors, it can garnish houseplants. A layer of dark stone underneath the chips only heightens their dazzle.
Architectural elements and accents are also good uses. Think Zen gardens, areas around statuary, or between pavers.
For more impact, place rope lights below a deep layer of the mulch for a glowing display in the darker hours.
In general, if you like its appearance, glass mulch can provide a pulled-together, finished look to your garden’s beds and borders.
• Rinse and soak chips to remove glass sand and bottle labels. For large installations, rain will do this for you.
• Layer cardboard between the soil and the glass when using plants. It will decompose and a layer of compost will develop. Choose high quality soil to reduce the risk of weed seeds. A generous layer of glass will need less frequent topping off.
• If you use the mulch in a walkway, channel, or foot traffic area, a hard layer underneath adds stability and prevents mulch from sinking in the soil.
• A leaf blower clears away surface debris.
ON A TRIP TO A PROCESSOR
• Wear closed shoes and bring gloves.
• Take plenty of sturdy containers. Glass is heavy and, depending on the container’s size, it may be easier to maneuver when only half-full. A full contractor’s bucket, for instance, weighs roughly 60 pounds.