Which Plastics Are Safe to Use as Containers to Grow Food?

Gardening outdoors may not be an option if you have limited space or a short growing season. Enter "container gardening," where you sow seeds in containers rather than the ground. And using safe plastic planters for vegetables and other sprouts can help you make the most of your little garden.

So, why exactly is it important to know which plastics are safe for gardening? Well, it's possible for the chemicals in certain types of plastic to leach out, according to the University of New Hampshire.

That said, while it's typically better to grow food in the dirt and away from toxins, it is safe to grow vegetables in plastic containers so long as the planter is made of certain types of plastic approved for use with food. Here are the safest types of plastic tubs for gardening to help you get started.

High-density polyethylene (HDPE) is a type of food-safe plastic used in milk jugs, water bottles, trash bags and some buckets, according to the Environmental Protection Agency (EPA). You can identify HDPE by locating a triangle with the number 2 on the bottom of your container, per the EPA.

HDPE planters are typically considered safe containers for growing vegetables. What's more, HDPE is recommended as a type of food-safe plastic sheeting for garden beds that are made of treated wood, as this type of plastic can shield plants from the chemicals in the wood, according to Iowa State University.

However, if your garden is outside in your yard, it's important to remember that HDPE containers aren't typically made for outdoor use — exposure to the elements can break them down, so it may be wise to replace these planters often, according to the University of Maryland.

Low-density polyethylene (LDPE) is another common plastic also used to make milk jugs, water bottles and trash bags, according to the EPA. You can identify it by finding a triangle with the number 4 on the bottom of your container.

Similar to HDPE, this type of plastic can be used as sheeting to protect your plants from chemicals in treated wood, according to Iowa State University.

But you may have to replace them often, per the University of Maryland, as this type of plastic can break down.

Polypropylene (PP) is a strong plastic often used to make caps and lids, denoted by the number 5 on the bottom of a product, according to the EPA.

PP has a high melting point and is approved for food contact, according to the U.S. Food and Drug Administration. And when it comes to growing plants in plastic containers, this type of plastic is also sometimes recommended as a cover to protect sprouts against elements like frost, per New Mexico State University.

PP fabric liners can also be used to protect plants from the chemicals in treated wood, according to Iowa State University.

Polylactic acid (PLA) is a newer type of plastic derived from renewable resources like corn, wheat and rice, according to December 2016 research in ‌Advanced Drug Delivery Reviews‌. It's most commonly used as a material for 3D printing.

But it may also make for a safe plastic planter for vegetables and other plants. That's because the material is bio-based and compostable, making it less of a concern for soil contamination.

Polyethylene terephthalate (PET) is a clear, tough plastic mostly used in water, juice and soda bottles, identified by a number 1 on the bottom of a product, according to the EPA.

PET is considered safe for single use, but less safe as a reusable plastic container because it can release harmful chemicals like bisphenol A (BPA) over time, particularly when it's heated up, according to a September 2014 study in ​‌Environmental Pollution‌.

While this is more cause for concern if you're hoping to reuse plastic water bottles, it still may be best to opt to grow vegetables in plastic containers made from different types of the material.