Coconut shells

I recently harvested a compost pile, a pile of the leave it there and let it do its thing without interference variety. Essentially, we just put kitchen scraps mixed with some dry brown stuff on the top of the pile and let it do its thing for several years. So, to get to the point, when I harvested the pile recently, I discovered, in addition to a few plastic spoons (toddler additions most likely), most of a coconut shell at the bottom of the pile. So, my question is, just how long does it take a coconut shell to decompose?

Forever. Part of why it makes such good charcoal. Crack it up and put it in the soil, it will be a carbon source for years to come.

As you've discovered, coconuts take a long time to degrade. Therefore I do two things with my coconuts.....make biochar with them or put them in my biotrash pits (large pits filled by hugelkultur method).

I'm glad to see it isn't just me, then... I am considering putting some holes in the bottom of the shells, and using them as small planters since they don't compost.

Thanks for all the tips; might indeed try to put the coconut shells directly into the soil, as I too have been wondering how to compost them.

In regards to using them as planters : be careful to not overwater them though, there had been a lot of rain when I had just experimented with coconut shells as planters [with holes in the bottom, as there's this hard shell that retains the coconut water that I guessed would retain the water too], and the water would just not flow through correctly, and ended up drowning the seedlings....

I use shredded coconut shells for vermicomposting (redworm composting) bin filler. . .as already noted it lasts a long time. Shredded, it still lasts 2-3 years.