How to Choose Second-Use Items for Container Gardening
Since container gardening has become even more popular, and getting a second use out of materials becomes ever more important, we want to take a moment and explain some of the best (and worst) items to use second-hand for gardening. Before choosing any item ask yourself these questions to get a better understanding:
Where did this item come from?
This is by far the most important question to ask yourself before choosing a container. See a clay pot on the curbside? Seems perfect right? The truth is you have no idea what that pot was used for and why it is being thrown out. That clay pot could've been tossed because it became moldy, became infested, or was used to store hazardous material. General rule of thumb is to use YOUR second use items; not only do you personally get a second use of your own materials, but you also know the complete life cycle of the item.
Always try to figure out what the item was used for if possible. Sanitize the item thoroughly even if it appears to have been used for plants. If the item was used for food storage, it most likely can be used for container gardening.
What material is the item made of?
Always choose natural materials when possible. Although biodegradable pots have become more widely available, by design it may be difficult to find as a second use item. Glass is a great option, as many food items are stored in glass, and glass items are frequently thrown out along with plastic. Plastics, unfortunately, will be the easiest material to find and get a second use from. Not all plastics should be used however, as they may leach toxic chemicals into the soil such as BPA, phthalates, and others. Recently it was discovered that 99% of Americans had phthalates in their urine when tested. One 2015 study found phthalates in the tissue of carrots, lettuce and strawberries that were absorbed through their roots. Plastics generally should be used with caution. ONLY use food grade/food safe plastics if you decide to go that direction (see below for details). If using plastic materials pay extra attention to temperature changes and abrasions to the plastic material; this is when plastics will most likely release chemicals.
Some egg cartons, and the roll from paper towels are made from biodegradable material and are great for transplanting. You can see how they compare along with other items in our other guide.
Find the plastic code
On most plastic materials you will find a plastic code. Labeled 1-7 this marking is internationally recognized and will determine the material of the item and how it should be recycled. This code is generally imprinted on the bottom of the item. Take a look at the picture below and you will see the recycling symbol with a number in the middle. You probably see this symbol several times a day without realizing it:
This specific item has a "2" plastic code, which means it is made of High-Density Polyethylene.
Plastic codes explained
Code 1: polyethylene terephthalate (PET)
Most commonly used in single use plastic bottles. Although food safe, code 1 plastics should generally be avoided for planting because they are solely designed for single use. Use with caution.
Code 2: high-density polyethylene (HDPE)
Most commonly used in milk jugs. This is a hard plastic considered food safe and can be used for gardening.
Code 3: polyvinyl chloride (PVC)
Most commonly used as piping, PVC is very widely used despite it's known cancer risk. This plastic is known to seep into soil and should not be used for container gardening. Always avoid.
Code 4: low-density polyethylene (LDPE)
Most commonly used in plastic bags. This plastic is considered food safe and can be used for gardening.
Code 5: polypropylene (PP)
Most commonly used in food containers and pill containers. This plastic is considered food safe and can be used for gardening.
Code 6: polystyrene (PS)
Most commonly used in styrofoam this plastic is made of a known carcinogen. Although this should be avoided when directly used as a container, styrofoam works great to house other containers due to its insulation properties. Always avoid direct contact.
Code 7: every other plastic
Code 7 is basically a fancy way of saying "other." Any plastic that does not fall into another code gets labeled as code 7. Although there are RARE exceptions, always avoid.
What are you planning and how are you growing your plants?
Different plants need different containers. Indoor plants have different needs from outdoor plants, and plant varieties have different needs in terms of container depth. All of this will help determine which size and what material is best.
Outdoor- Always pay extra close attention to the material used. Outdoor growing means your container will be subjected to weather and heat which means it should be made from a very stable material. If using plastic, use extra caution, as this form of gardening will be most likely to leach chemicals into your soil.
Indoor- Consider using items that come with a clear lid. This will help with retaining humidity during germination and will produce a mini green house effect during the infancy of the plants.
Transplanting- Highly recommend trying to find biodegradable material. Biodegradable materials are perfect for transplanting because they are stable enough where you can start them inside, but are generally weak enough to allow roots to pass through. The best part is you don't have to fiddle with trying to get your plant out of the container because the container can be planted directly into the ground.
Container size- Always take into consideration the complete life cycle of the plant. Depth is as important as width. Tubers (beets, carrots, parsnips, and turnips) will need a much deeper container than others. Always check our free online grow guide to see the needs of your particular plant.