Uprooting plastic: Why and how to reduce plastic in the garden

Plastics took root in garden culture around the mid-19th century: “Commercial farmers began switching from reusable terra-cotta pots and biodegradable burlap to single-use plastic containers and bags during and after the 1960s,” says Erica Cirino, communications manager for the Plastic Pollution Coalition and author of “Thicker Than Water: The Quest for Solutions to the Plastic Crisis.” Plastic was more durable and flexible and often cheaper than traditional materials. In the decades since, plastic has been adopted for a multitude of  horticultural purposes, including mulching and cladding materials in greenhouse manufacture.

The bad and the ugly of plastic in the garden

Although plastic has great utility, it also poses significant dangers. For eco-conscious gardeners such as Petersen, the crux of the issue lies in how plastic disintegrates into microplastics, and how the chemicals designed to make plastic flexible and durable — such as phthalates and bisphenol A (BPA), respectively — leach into garden soil. “Studies have shown,” says Cirino, “that plants take up microplastics through roots and leaves.”

The Rodale Institute, an organization that researches and promotes organic growing practices, estimates that for every acre of land farmed using plastic weed barriers, between 100 and 120 pounds of plastic end up in the landfill or break down into a farmer’s field. As plastic decomposes, it releases greenhouse gases into the atmosphere or breaks down into tiny microplastics that are absorbed by a vegetable’s root system, accumulating in the plant tissues and eventually ending up in some foods. According to two new studies from Rutgers Health, “Micro- and nanoscale plastic particles in soil and water can significantly increase how much toxic chemicals plants and human intestinal cells absorb … [raising] fresh concerns about food safety from plastic pollution.”

Plastics in the home garden pose similar risks. Plastic weed barriers, for one, are also used by gardeners to suppress invasive plants. On top of releasing toxins and microplastics into the soil, they also prevent water and airflow from getting deep underground to the root of the plant. This can suffocate the underground microbial life responsible for carrying essential nutrients, such as nitrogen, to the plants.

Instead, Petersen recommends bypassing plastic for another alternative. “For the weeds, I’ve been using wood chip mulch and cardboard,” she says. When you top-dress your soil with mulch instead of plastic weed barriers, some nitrogen at the surface gets locked up, which helps inhibit weed seed germination. But as mulch decomposes, it increases nitrogen in the soil — something plants need to grow.

Recyclables aren’t an easy fix

Even though recycling plastic or using recyclables may seem like a great solution for keeping plastic out of the landfill, it can pose significant problems for the garden. There are seven types of plastic that, in one form or another, are all used or can be found in garden tools and equipment. The small triangle with a number in the center is a decoder ring of what can and cannot be recycled.

Type 1, PET (polyethylene terephthalate), is typically used in garden netting and containers. It is one of the most common types of recycled plastic. However, it breaks down in sunlight, something gardens have in abundance. Over time, some PET products may release phthalates, chemicals that have been linked to reproductive issues, heart disease in older adults, and numerous other deleterious health and environmental impacts. What’s more, netting can clog recycling machinery, making it unrecyclable.

Type 2, HDPE (high-density polyethylene), is found in nursery pots. But in many instances, the HDPE plastics used by horticulture supply companies are black — a color difficult for the near-infrared recycling sorters to discern as clean or dirty. Instead, many head straight to the landfill.

Then there’s the rest. Type 3, PVC (polyvinyl chloride), common in irrigation systems, also leaches phthalates into garden soil when exposed to sunlight. Type 4, LDPE, used in hoses and drip lines, must be squeaky clean to recycle. Type 5, polypropylene, is used for plant pots, landscape fabric and in gardening tools like hand forks or trowels. Not all polypropylene products are created equal, and many will degrade when exposed to UV light and extreme heat; this raises concerns about its long-term impact on the environment after disposal and if it can be recycled — a process requiring high heat. Type 6, polystyrene, crumbles into microplastics.

Plastics that don’t fit into the first six categories are stamped as Type 7. These aren’t easily recyclable, and are often mixed with other materials that are impossible to separate (for example, fleece frost covers are made using a combination of plastic and cloth). Biodegradable, vegetable-based plastics are generally labeled as #7; they present their own environmental challenges and also are not recyclable.

Cirino adds: “When plastic is actually recycled, which is rare, manufacturers mix in a large portion of newly made plastic or toxic additives to shredded, melted-down plastic waste to restore some of its desirable properties.” This degrades the quality of the new product being made, and eventually this lower quality item will not be able to be recycled further and will ultimately end up in the landfill.

The EarthWays Center at the Missouri Botanical Garden reports that more than 350,000 pounds of horticultural plastic ends up in U.S. landfills annually. Here, all that plastic continues to leach toxins and break into microplastics that seep into waterways and oceans, further affecting the food chain. The botanical garden also reports that in 2022, public plastic pot recycling was discontinued in their region because the kind of plastic used to manufacture garden containers has a negative value in the recycling industry — in other words, it simply wasn’t worth the cost.

Plastic alternatives

There are companies offering nonplastic options, particularly for containers and pots. For example, the company CowPots, founded by dairy-farming brothers in Connecticut, makes garden pots from composted cow manure. The manure is processed through a methane digester that captures gas for energy, returns liquid to the fields and turns solids into odor-free, weed-free garden pots.

RootMaker, an Arkansas-based horticulture company, recently worked with Footprint, a manufacturing company developing plant-based fiber solutions, to create a biodegradable pot for its product line. “We’ve been testing alternatives to plastic for a number of years now,” says Wayne Hinton, founder of RootMaker. Their BioPot improves water retention, reduces root rot and keeps plants cooler than its plastic counterpart. It is made of biodegradable cardboard, which breaks down in the soil, where it is consumed by microbes.

Taking responsibility

One possible solution to gardening’s plastic problem could be Extended Producer Responsibility (EPR) legislation, which makes producers financially responsible for collection, sorting and recycling. “Switching the burden of the costs of managing materials from taxpayers to companies in theory should encourage the companies to use less packaging and opt for materials that are more recyclable,” says Cirino. However, she also cautions that EPRs can only succeed if legislation incorporates specific plastic-use reduction requirements, as well as standards for recyclability, recycled content and elimination of toxic substances. But because manufacturers view these responsibilities as burdensome, they’ve lobbied hard to blunt the passage and implementation of effective EPR laws in the U.S.

“Thankfully, most of what you need to build a plastic-free garden is available in local hardware stores,” says Cirino. That includes basics like untreated wood for raised beds and metal trellises for climbing crops like peas and beans. Here are a few more ideas.

Upcycle: Pick up used garden tools at yard sales, community swaps or thrift stores.

Buy in bulk: This reduces plastic packaging. Petersen avoids plastic packaging by purchasing loose soil and compost in bulk from her local garden center and having it delivered.

Make your own compost: Compost adds nutrients to the soil, and making it at home reduces food waste. (If you need guidance on getting started, check out FoodPrint’s Compost 101.)

Share: Donate the plastic pots and seed trays you no longer need to a local farmer or farmer’s market. This not only keeps plastic out of the waste stream, but also supports smaller growers.

Plant labels: Use wooden popsicle sticks or paint names on rocks with waterproof paint instead of plastic tags.

Ties and supports: Trade plastic ties and netting for jute twine, burlap strips or wire mesh — all durable and compostable or recyclable. Even strips cut from old towels can become garden ties.

Advocate: Support nurseries committed to reducing plastic, especially those that ship without plastic packaging or offer garden pot return programs. Ask your local garden center if they have plants available in biodegradable pots.