Which Plastics Are Safe for Gardening

Last Updated on October 31, 2021 by Phil

“Which plastics are safe for gardening?” That’s a question I asked myself when I was starting out with gardening. And, it is something I still hear a lot today it is a common question I get once people know I spend quite a bit of time around plants.

Whether you’re into soil gardening, hydroponics or aquaponics, you’ll likely deal with a lot of plastic products when setting up your garden.

More importantly, if you’re growing food for your family, it is essential that everything you use is safe for health, not just in the short term but also for the long term.

As such, I’ll go in depth about the different kinds of plastics and which ones are safe for gardening. Along the way, you’ll also see some types of plastics that are unsafe and which you should avoid when planting.

Table of Contents

What Kinds of Plastics Can You Use for Gardening?

When it comes to commercial plastic products, there will be 7 kinds you’ll see. Each of them are different. And, depending on what you’re using them for, you may choose one over the other.

Also, their costs vary.

As you would expect, the better quality ones will be more expensive.

For gardening, you may or may not want to use plastic products depending on what your goals are. For example, if you’re looking to be more environmentally friendly, then plastics are probably not the best option.

Another thing to consider is organic gardening. This also eliminates plastics or at least minimizes their use.

You likewise want to be more cautious when growing vegetables, fruits or herbs since you’ll be eating the harvest.

The good news is, plastic products come with labels. They are numbered according to the type of plastic. So, all you need to do is check for the triangle label on the product and compare it to the descriptions below.

Plastic Type 1 – PETE (PETE or PET bottles – Polyethylene Terephthalate)

This is probably the most common type of plastic you see because it is used in drinking water bottles. You’ll also see them in soda bottles as well as peanut butter jars.

PET or PETE bottles are recyclable.

But as you probably already know, they cannot tolerate very hot conditions otherwise they’ll leach chemicals. As such, don’t leave your bottled water or other bottled products in the car during very hot summer days.

Also, as you’ve probably noticed, over a long period, the material also breaks down, albeit slowly. It tends to deteriorate faster with repeated or continuing exposure to heat and light.

This is why water bottles are designed for single use.

Another thing with this kind of plastic is it will take on the smell of whatever has been in there.

Overall, type 1 plastics are okay for gardening. But, ideally for indoor or somewhere away from the heat and sunlight. While they will work, they’re not the best option.

That said, if you’re on a budget and you’re not going to plant vegetables, fruits or herbs in the pot, it will work fine.

Plastic Type 2 – HDPE (High-Density Polyethylene)

HDPE is also called high density polyethylene. These are similar to type 1 plastics but have higher density. As such, it is also more costly.

Like PET and PETE you’re also familiar with these products as they’re commonly used for beverages and household products. The two most popular are milk jugs and detergents.

You’ll easily notice they are thicker, slightly heavier and don’t have a translucent appearance. This makes them stronger, sturdier and longer lasting. They are also harder to breakdown which is good for regular use.

Like type 1, type 2 plastics are recyclable as well.

The best thing about HDPE is that it is safe for food consumption as well as beverage storage. Its high density structure also makes it resist sunlight including the ultraviolet rays.

Just as importantly, it will tolerate cold and hot conditions (from -148 degrees Fahrenheit to 176 degrees Fahrenheit). This makes it great for gardening even during the hottest times of the summer.

And, you can leave them in the cold outside during the winter and not worry about them degrading.

Plastic Type 3 – V (PVC or Polyvinyl Chloride)

This is another type of plastic you’re probably familiar with. But, unlike the two above, you’ll see these used for tools and objects outside the house.

PVC is most commonly used for water pipes.

Yes, that’s the hard plastic that comes down the side of your home or for other piping needs.

While strong and sturdy, they are known to leach chemicals when left under the heat. These chemicals include phthalates, which helps make the product durable yet flexible.

Unfortunately, phthalates are toxic to humans as they mess up our hormones. This can lead to long term health problems including abnormalities in reproduction.

Additionally, they can only be recycled in a specific way.

As you can already guess, it is a good idea to avoid PVC in your garden. That said, some type 3 plastics don’t contain phthalates. As such, these are okay to use. However, you need to be absolutely sure that the manufacturer is reliable.

Plastic Type 4 – LDPE (Low-Density Polyethylene)

LDPE is much like type 2 plastics (HDPE), but the material is not as dense.

Like those above, you’ll likely come across these. LDPEs are often used for squeeze bottles, food storage bags and shrink wraps.

These are reusable. But, they are not always recyclable.

In the garden, you’ll see them used as polytunnel covers as well as in compost bags.

Since it is being used for food and in the garden, it should be safe to use in your yard as well, right?

If you said yes, you’d be correct!

Like HDPE, LDPE is able to tolerate varying temperatures. You’ve probably tested this without knowing it since you’ve likely placed some LDPE plastic products in the microwave before.

Plastic Type 5 – PP (Polypropylene)

Polypropylene is a word you’ve probably come across. It is easy to remember because it sounds very different from other words. Plus, next to PVC it is the most produced plastic in the world.

This type of plastic is commonly used in microwaveable trays, food containers, bottle caps, yogurt and margarine tubs.

While it is not able to tolerate heat as much as LDPE and HDPE, it is still safe to use in the garden as well as food products.

As such, you’ll see it in garden centers in the form of pots, netting and trays for plants.

Plastic Type 6 – PS (Polystyrene)

Type 6 plastic is Polystyrene. It is widely used for many different products. The most common ones you’ll come across include styrofoam food containers and cups. Also, there are plastic forks and food trays made with them.

If you buy eggs that don’t come in the cardboard cartons, then the plastic holding the eggs are likely Polystyrene plastic.

Since it is used for food products, it is also safe for gardening, right?

Well, yes. But, not as safe as HDPE or LDPE.

The good news is it has gone through lots of studies that say it is safe for food. But, there’s still lots of conflicting data and uncertainty about microwaving it.

For gardening, it is likewise safe.

Again, it is a decent plastic to use, but not the best one. I find that it is more porous which can be good for letting excess water escape. But, structurally, it is less sturdy and less likely to last as long.

As such, there’s not problem in using type 6 plastics for gardening. But, there are better options like HDPE and LDPE.

Plastic Type 7 – Other

This covers all the other plastic products that not covered by the other 6 types above.

As you can guess, there are many kinds here. But, most of them are toxic or not recyclable, some both.

Many type 7 plastics are made from Polycarbonate or Polylactide, with the former being the most common. Unfortunately, it leaches BPA which is harmful to health in the long term.

Because type 7 plastics are often harmful to health or toxic in one way or another, this is something you want to avoid for food and gardening.

Which One Should You Choose to Be Safe?

From above, 4 of the 6 types of plastics are deemed safe. These include

Type 1 – PET and PETE
Type 2 – HDPE
Type 4 – LDPE
Type 5 – PP

And while you shouldn’t have any problems with any of the 4, it is good to keep in mind that 2 are better than the other 2.

The 2 safest plastics to use for gardening are HDPE and LDPE. Unfortunately, they do cost more as well. As such, you’ll want to weigh the pros and cons of cost to health and safety.

For plants that are not edible, you can go with PET/PETE or PP to save some cash. But, for those that you’ll eventually end up consuming, use the higher quality plastics just to be sure.

If you’re into recycling, you’ll need to consider it into your decision as well.

Can You Grow Plants in Plastic Pots Safely?

Yes.

You probably already know that from the descriptions of the different types of plastics above. The key is to choose the right kind of plastic to use to ensure safety.

Of course, many gardeners opt for other kinds of pot materials including terra cot, metal and so on.

But plastic pots are cheaper, lighter to carry, very durable, don’t crack or break if you drop them, flexible and strong.

You can also get them in all sorts of colors. And, in many cases (but not all) are recyclable.

As long as you choose the right kinds of plastic, you need not worry about safety or health with plastics in the garden.

How to Grow Plants in Plastic Containers

In addition to knowing what kinds of plastics to use and avoid, knowing how to use them also helps. This way, you don’t compromise the material (especially for the cheaper, lower quality types) and prolong the life of the products so you don’t need to go out and buy more in the future.

Here are my top tips.

Always check the kind of plastic. Types 1, 2, 4 and 5 are all safe for gardening. Both types 2 (HDPE) and 4 (LDPE) are your best options assuming that you don’t have a problem with spending extra. Types 1 and 5, in many cases, the latter, will make up the budget gardening plastics you’ll be using. It is also handy to keep in mind that anything with BPA or other toxic and chemicals are no-no’s. So, skip them even if they’re on sale or look really cheap. It’s just not worth the long term risk.
Avoid keeping them under very hot conditions. If possible, help keep them cool during the worst times of the day or year. These are during the afternoons as well as the peak of summer. The higher the temperature and the lower the quality (cheaper) the plastic, the more likely they can degrade over time. Additionally, black and other dark colored containers may look awesome. But, they also absorb more heat and sunlight compared to light colored plastics.
Use potting soil with high organic material content. Here’s an interesting one. You already know why more organic matter is better for plant growth and health. But, in addition to that, the organic matter will help catch some of the leached chemicals (in case that happens) to prevent or reduce the amount that actually reaches the roots.

Conclusion

Hopefully, this article gives you peace of mind knowing that using plastic is safe in the garden.

Although, I do need to qualify that statement since only certain plastics are safe to use for gardening. The others, including those with BPA and other chemicals or toxics, you should avoid.