Which Plastics Are Safe For Gardening?

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One of the more common questions I’m asked on the blog is about plastic use, specifically, “What plastics are safe for use in the garden?”  Since a lot of Epic Gardening readers are into hydroponics and aquaponics over soil gardening, there are a lot of people with a lot of plastic in their setup that are curious about their safety and place in the garden.

Well, I was curious too, so I decided to go deep into the world of plastics and figure it all out for you all!

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Here’s what I found.  It turns out there are 7 different types of plastics that are labeled.  If you’ve ever seen those little triangles with a number in it on your plastic products, you’ll know what I’m talking about.  Here’s a picture:

Below is a breakdown of what each type of plastic is, what products use it, and if it’s safe to use in the garden.

Plastic Type 1 – PET

Plastic marked with a 1 is made of Polyethylene Terephthalate, or PET.  It’s one of the most common plastics for food items like soda bottles, jars of peanut butter, or if you’re like me, jars of ghee you use for cooking.  One of the issues with this type of plastic is that it tends to take on the aroma of the food that is stored in it.

It’s one of the most commonly recycled plastics and is almost exclusively used for single-use items since it can break down when exposed for long periods of time to light or heat.

If you’re paying attention, that means it’s not the best choice for your garden, since ​gardens typically are exposed to quite a bit of light and heat!

Yes, it’s probably going to be fine, but why take the chance of some leaching, especially when you’re running a soil-free setup, meaning that the leached chemicals will go straight into your reservoir rather than the bit of soil next to the plastic.

Verdict: While it’s probably OK to use, there are better plastic choices out there, so why not use those instead?


Plastic Type 2 – HDPE

High Density Polyethlene
Source: Public Domain Photos

Plastic marked with a 2 is made of High-Density Polyethylene.​  You see HDPE everywhere, from milk jugs to detergent bottles.  It’s one of the best and safest types of plastic for food consumption as it resists UV rays and is extremely heat tolerant ( -148 to 176 F / -100 to 80 C ).  Because of this, it’s an excellent choice for the garden.

Verdict: Very safe, not known to transmit any chemicals into soil or food.  An excellent choice for the garden.


Plastic Type 3 – V

Plastic marked with a 3 is made of Polyvinyl Chloride​, better known as PVC.  One of the more commonly known types of plastic, PVC shows up in plastic pipes, irrigation, salad dressing bottles, and liquid detergent containers.

Most PVC products contain chemicals known as phthalates, which essentially help the PVC be more durable, flexible, etc – all of the qualities we associate with plastic.​

While this is great for making PVC a quality building material, phthalates are not the best for us humans.  In fact, most of us have some small concentration of phthalates in our urine due to leaching, though the CDC believes that our diet is the reason for most of the phthalates in our bodies.​

For this reason, try to stay away from PVC setups in your gardens.  I know it’s attractive to have a cheap PVC garden, but if you value your health, choose an alternative plastic.

*Note: not all type 3 plastics use phthalates as a plasticizer, so you may be OK using some PVC products – but be sure you know that phthalates weren’t used before you make the decision.​

Verdict: We’re already exposed to enough phthalates in our daily lives, why grow with a material known to leach them into the environment?


Plastic Type 4 – LDPE

Plastics marked with a 4 are made with Low-Densidy Polyethylene.  Some products that use LDPE include plastic produce bags, trash can liners, and food storage containers.

Are you seeing a trend here?  The plastics that are already used for food storage tend to also be safe to garden with.  Like it’s older cousin HDPE, LDPE plastic is very safe in a wide range of temperatures and can even be used in the microwave.  Conclusion?  It’s a good choice for the garden.

Verdict: Very safe, not known to transmit any chemicals into soil or food. An excellent choice for the garden.


Plastic Type 5 – PP

Plastic marked with a 5 is made of Polypropylene​.  Commonly used in products that require injection molding like straws, bottle caps, or food containers.  While it’s not as universally tolerant to heat as HDPE or LDPE, it generally is safe for use with food and the garden.

There are some minor concerns about leaching that came up after Canadian researchers found that the leaching was affecting their labwork, but for the most part it’s regarded as a safe plastic ​

Verdict: A decent choice for the garden.


Plastic Type 6 – PS

Plastic marked with a 6 is made of Polystyrene​.  You see polystyrene based plastic everywhere – packing peanuts, styrofoam cups, plastic forks, meat trays, to-go containers, etc.  It’s one of the most widely used types of plastic in a variety of industries.

​Being so widely used, it’s also been the subject of many scientific tests on health and safety.  The general conclusion is that it’s safe for use in food products, which doesn’t necessarily mean that it is safe for gardening.

One interesting fact is that the food products that are contained in polystyrene (meat, berries, etc) all have styrene as a naturally occurring compound.  Polystyrene is a continual topic of discussion in scientific circles due to it’s wide use.  One particularly popular topic is the safety of microwaving polystyrene products with food – the jury is still out on that one.

All in all, it’s a decent plastic to use for the garden, but my only concern is that it is a more porous material and less sturdy, making it not a good structural choice for the garden.​

Verdict: Seems fine safety-wise, but structurally may not be the best choice for the garden if you need it to support weight or water.


Plastic Type 7 – OTHER

Polycarbonate

 

Plastic marked with a 7 is made from anything other than the materials listed in numbers 1-6.  Typically this means plastics made of Polycarbonate or Polylactide​.  Polycarbonate is the most common type 7 plastic, and also one of the most harmful plastics that we have ever created.  It’s been proven time and time again to leach BPA, which has been linked to a lot of different health problems.

The thing to know about plastic type 7 is that it’s a catch-all for anything that doesn’t fit into the first 6 categories.  That means that there are also some safe plastics in this category as well, but you’ll have to do further research to make sure that you’re using one that’s safe.

Why go through the trouble when there are other, safer plastics to use like HDPE or LDPE?  My vote is to stay away from type 7 in the garden simply due to better options elsewhere.​

Verdict: Some type 7 plastics contain BPA, a harmful compound that has been linked to many adverse health effects.  Stay away from type 7 plastics in your garden.


Which to Choose?

Hopefully this breakdown gives you a good idea of what to look for when it comes to using plastic in the garden.  I’m all for recycling materials and using what you can to build out your garden, but not at the expense of your health or the health of the people who are eating what you’re growing!

My personal choice is to go with HDPE or LDPE, just because they’re the safest by far when it comes to actual scientific tests and potential concerns.  Yes, they’re a bit more expensive to purchase, but they last a long time, which means they’re actually cheaper when you consider the fact that you won’t have to replace them often.


Have any thoughts or suggestions about plastic use in the garden?  Let me know below!

Knowing which plastics are safe for the garden is key to making sure you don't use harmful materials that leach chemicals into your food.
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45 thoughts on “Which Plastics Are Safe For Gardening?

  1. Thank you! I’ve read about ten answers/articles on this subject- yours is the BEST! You provided the most information and reasoning about the appropriateness of each type of plastic to use for vegetable gardening and composting. Some articles presented in response to my search did not even address the issue (including one from a well-televised gardener). Thanks again!

  2. Thanks for this research and article! My dad broached the topic of hydroponics for both of our new gardens, and because we live in Hawaii, my first concern was leaching, because the sun is SO brutal here. Seeing that PVC pipe might not be an ideal option, I’m curious what you’d use as a substitute? So many of the DIY plans I see are PVC dependent.

    • Yeah, PVC *should* be fine but in extreme sun conditions I’d be cautious – no reason to risk if possible. HDPE will be your best bed, but it is definitely more expensive. You can also cover your PVC with shade cloth or something similar to reduce UV exposure.

  3. Hi,
    My question is about soil (composts or soil amendments as well) being sold in large flexible soft plastic bags. These sit out in extreme temperatures. I’ve purchased some recently on several 85 + degree days in a row and they sat out on the sun. Are there plastic chemicals leaching into the soil products? then therefore are these plastic chemicals hanging out in a garden , possibly being taken up by edible plants?

    • I hear you on your concern Maureen. This is one of those things that’s something you have to either get around by not buying soil in those types of bags, or play the risk vs. reward ratio on the leaching. As far as I know they don’t sit out long enough to leach much into the soil, if anything. But I haven’t studied it in depth enough to provide a conclusive answer.

  4. Merci pour ces explications claires et bien utiles pour mieux comprendre ces composants plastiques.
    Je vais partager cet article

  5. I been thinking about this for a while, I been gardening for two years and only use the orange containers from HD but this year am growing a larger crop and need it more container, I have a friend who give me 100 use 5 gallons paint container and I didn’t know is they would be safe, thank to your article now I know that they are HDPE, also I look at the HDs containers and to my surprise they were also HDPE so all is good to for my little backyard farm, of course I will be cleaning the containers before using them.

  6. I recently bought some black plastic bins that were the perfect shape and size for my hydroponics, but I noticed when I got them home that they have a weird chemical smell when they are warmish. Instead of having the typical triangle symbol, they are marked “Recycled Plastic”, which implies they could contain anything. So I’m thinking these aren’t worth the risk? I thought of lining them with a trash can liner, but these are also marked “Recycled Plastic”.

  7. What about UV degradation, you twit? Many of these plastics are made from molecules that are fine while linked together, and therefore unavailable to be absorbed into soil or plants, but are reactive to sunlight UV and break off into individual subunits that are SERIOUS carcinogens. EG polystyrene + UV = many individual styrene subunits.

  8. So I am going to use some large galvanized metal water troughs for some planting beds… Not wanting to have to fill the whole thing with soil, so looking at what I can use to fill up the bottom a bit that isn’t going to end up leaching chemicals into my soil… From reading your post, I could use plastic milk jugs? Other thoughts?

  9. We have a use in mind that puts re-usable fertilized water not taken up by plants during a two hour period back into a mixing tank to be brought up to par and in the process it travels six inches into collector and then on to the safety food grade protected mixing tank another 6-8′ away. Do we need this recommended CPVC quality in both short sections to avoid 1ppm detection of disinfectants, etc. being leached out?

      • When the government invented the EPA, the FDA, and maybe a dozen or more others among hundreds, all trying to survive by proving that they are essential to human survival, they get very anxious to prove some evidence and if this exposure is more deadly than cyanide, they will be praised for shutting down every non-conformer. Of course,most of the world will still see expanding population no matter how many drop dead of such toxic exposure in Uganda or Nigeria, for example. So your being ‘save’ is more a political choice than a scientific one…isn’t it?

        • Actually, the industries that make these synthetic products, including medicines and food (much of which is synthetic) have so much money and such powerful lobbyists that the FDA overlooks the dangers of these products rather than announcing it to public, let alone regulating it. It is after a sufficient number of people have suffered disease and died, that the problem becomes politically charged enough for them to make small announcements that there may be some danger from these substances. It takes a good while for them to completely ban these poisons, if they ever do. So erring on the side of safety, is in our own best interest.

          It is not a question of increase or decrease in population that is of concern here, rather of a disease ridden, suffering world.

          • You win! Lets have a disease free environment in which starvation wins the honor of killing most humans; or can you invent a food that also kills the disease causing impurities?

          • There is no reason people should starve on this planet. The amount of food thrown in garbage each day in most western households can feed the hungry all over the world; add to it the dairy and crop that is purposefully dumped by producers because it’s more than they can sell. The main disease we have is lack of awareness and apathy.

            One reason underdeveloped countries have overpopulation is because they need their children as old age insurance to look after them. Not all children survive and not all will be capable of looking after them. Another reason is lack of education and resources. In same countries, the better off areas have much lower birth rates.

          • Qudsia is right about surplus- in fact we pay huge subsidies to grow more corn, potatoes, and many other agricultural products to store or destroy. But, finding ways to preserve, store, protect, remove, ship and distribute is neither easy or without conflict from impact on value of what is otherwise paid to growers for what is sold. Ideally, government can control weather, and planting of all and distribute output equally to feed the entire world what it allows our species to eat- the same for all. Of course, it must also control DNA so all bodies need the same nourishment and do the same work in the same weather everywhere so as to only need minor adjustments for location or expense in getting food to them.

            Does this appeal to you as it did to the masters of the Soviet Union?

  10. What about Driveway Fabrics. They can be quite large and say they are polyethelene. (not sure if it is #2 or not.) Do you have any links to suggestions for large ground covering for weed barriers. Something like the large blue tarps but that is safe for vegetable garden? I have used poly tarps in the past but I don’t know if they are safe.
    thanks

      • Kevin thanks for the video. It was very informative. One thing that it lacked was a discussion on what types of tarps are ok? Also it sounds like he uses tarps to pre-treat the soil not as a continuous use throughout the growning season. Do you have any experience or know of any that have used tarps for the whole season and have considered the health effects of using plastic tarps. i.e. are some better/safer than others?
        thanks
        Jason

        • I would default to getting ones specifically made for horticultural use and just double check the plastic. It sounds like the one that you mentioned is iffy and you should stick to one that is created specifically for row cover / etc.

          • I will. garden mats company looks pretty nice, but the one thing I REALLY like about tarps is that they are big! I can get any size I want, put holes any where I want and every spring I can just throw it out like a bed sheet on my 10×20 garden. I till all the soil very well before so crop rotation isn’t that big of a deal and I’m not selling produces so a few less tomatoes isn’t a bad thing. the problem with garden mats company is like all landscape fabric. it is only 4 feet wide so I have to do multiple strips. while this seems trivial it is a pain. There is gaps, weed grow in between, blah blah.

  11. What about mesh/nets that we use for protection from pests, what are they made of? I also have a portable greenhouse that has clear PVC roofing/body, but is only exposed to morning sun. Will that affect my plants?

    • I am not sure what those are made of in every case Joy, but I would suspect that they’re quite safe as they’re not in direct contact with the soil in most cases. Your greenhouse should also be fine!

  12. Sometimes people use rain gutters purchased at home improvement stores to build a DIY nutrient film technique hydroponic system. Do you know what kind of plastic is used for rain gutters? Thanks.

  13. Thanks for a concise summary of the research. I don’t dispute that PVC has toxic chemicals that can leach and be broken down in the environment, but is there research that these chemicals are absorbed by plants?

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