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Adventures in Compostable Pots

4/09/2024


Last year, in search of non-black plastic pots, I went to my local gardening store and bought one of every single kind of compostable pot they were selling. Then, I went online and bought several other kinds of compostable pots in hopes that I might find one that was durable but also more Earth friendly. 


Peat pots are the most abundant and easiest to buy. Admittedly, they were initially great. They held decently to a degree, but some of them did start to tear and bust at the edges. However, I was happily willing to live with some problems to not add more black plastic to the world. I thought I had found a solution, but then I learned that peat has its own and serious problems with sustainability, which rules peat out for me.


One of the natural-fiber (non-peat) seed-starting trays I purchased had great promise. It seemed very sturdy, and considering that I was going to transfer the seedlings to four-inch pots, I didn’t think I needed it to be much sturdier than what they were. Unfortunately, I found that the seedlings’ moisture was very uneven. When I would come back to check on the seedlings, parts of the tray were very wet where other parts, especially on the edges, dried out too quickly. Problems were compounded when the trays started to collapse and warp on me in random places before the seedlings were ready to transfer. Finally, the lack of consistent germination along with the mildew and general funk that accumulated underneath the seed-starting tray was a deal breaker.


I fully admit that I could have done more to avoid these issues if I had been more diligent about not letting the tray sit in any amount of water for any length of time. Unfortunately, my schedule and my available seed starting area just didn’t allow for me to exercise that kind of diligence. Your mileage may vary. Given these constraints, I’m hesitant to recommend natural fiber seedling trays to most gardeners because of how quickly they either collapsed or dried out unevenly. An extraordinarily fastidious gardener with a tremendous amount of space and time could successfully pull this off, but a gardener with less time and resources available could find themselves disappointed and frustrated.


Other compostable, non-tray pots were promising, but they absorbed a lot of water, a few developed mold and mildew problems, and a few others collapsed faster than I could transplant them. Again, the time and attention required for these pots leaves me fairly reluctant to recommend them to anyone that isn't willing and able to be exceedingly attentive to their seedlings.


Finally, I found and have overall been impressed with the cow-manure based pots. They aren't perfect, and can be significantly more expensive than peat or plastic pots. However, I was pleased with how the seedlings did in the pots and how well the pots held up. I’ve only used one brand, but it seems reasonable to conclude that from brand to brand you could expect a solid pot that held its own, came from an abundant source, and would compost eventually. At the end of last year, I did end up throwing one of my very failed seedlings along with the cow-manure based pot into my cold compost bin and a significant portion of the pot is still there.


Common Issues for Non-Plastic Pots

  • Uneven moisture where the edges of the seedling-starting trays tend to dry out faster than the center

  • Some non-plastic pots will absorb a lot of moisture making it so the soil dries out, but the actual pot will still be quite moist

  • Mold/mildew can build up underneath the pots, especially with the seedling trays sitting in a tray

  • With non-plastic pots, it can be easier for the pots to split or fall apart before you're ready to transfer your seedlings due to moisture build up in the pot

  • Be prepared to be much more attentive to your seedlings, checking on them at least three to four times a day, especially if you're using a heating mat for your seedlings


Recommendations for earth-friendly solutions

  • Read about the harvesting of peat and understand why peat may not be as earth-friendly as you initially thought

  • If you are intent on using plastic pots (and I understand if you are), avoid black plastic if you can and look for other colors. Check with your local recycling facility and see what types of plastic they recycle. Reusing food-grade takeout containers with proper drainage might be a great option for starting seedlings.

  • Be careful not to flood your seedlings. Use just enough water, and a spray bottle can help with that, to keep the soil consistently moist. Too much water can prematurely compromise even the most durable compostable pot.



Tiffa Foster

RCMG New Member Committee

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