I had the pleasure of hearing Norman Smith from Mass Audubon talk about his work with snowy owls at the International Festival of Owls this year.  One of the things he talked about was that anyone can do science, or help with science projects.  You don’t need to be an expert, you just have to be curious and willing to devote a little time and energy.  You can either help with one of the many citizen science projects you can find on the internet or come up with your own. I decided to come up with one of my own.

I drink coffee almost every day, and I always end up just chucking out the leftover grounds when I’m done.  The other day as  I was trying to figure out what to do with some of my peppers, I wondered if the coffee grounds could make a good medium for plants.  A little bit of Googling revealed that coffee grounds contain a number of nutrients that could be beneficial to plants and encouraged spreading them around your garden.  Maybe someone has already tried this, but I didn’t find anyone that had done a side-by-side comparison of using them like a potting mix.  I decided to give it a try and see what happens.

I took a couple of cups and put my coffee grounds in one, and a commercially available potting mix in the other.  I used roughly the same amount in each cup and added enough water that they both seemed about equally moist.  I know this isn’t very precise, but I couldn’t think of any easy way to determine the moisture content of the two materials.  I decided that I’d just treat them roughly the same way and that would be close enough.  If an average person like me wanted to swap out coffee grounds for potting mix, it’s unlikely that they’d have the equipment necessary to get an accurate measurement of the moisture content.  They’d probably just dump some in a container and throw in some plants.  So, I’m doing the same.

It’s pretty easy to tell the difference between the two cups.  The coffee grounds are very uniform.  It’s just coffee grounds.  The potting mix is a mixture of soil, bits of what looks like mulch, and some little white balls that feel a little like pumice.

For my plants, I decided to use sweet basil.  I have a ton of sweet basil seeds, and I know they’re viable because the ones I planted in the AeroGarden came up pretty enthusiastically.  They stuck their heads out of their pods on the 4th day, so I have a pretty good idea of what to expect.  I decided 3 seeds per cup would be a decent sample.  Basil seeds are tiny.

I made 3 holes in the medium in each of the cups.  If you look really closely you can see them.  I was careful to try to keep each hole approximately the same depth.

I dropped a seed in each hole, and now we wait.  I’m expecting I should see something happen in about 4 days.  I don’t imagine that the medium will matter much as far as getting the seeds to sprout.  As long as they’re moist, I think they’ll germinate.  That’s my assumption based on the fact that I was able to germinate pepper seeds on a wet paper towel.  They didn’t need any special sort of soil to get them to sprout.  Sweet basil isn’t the same thing as a pepper, but I imagine that seeds in general behave similarly.  After they sprout, I can watch the two cups to see which one grows better.  Do coffee grounds work adequately as potting soil?  We should know in a few weeks!