Most people never stop to think much about the little white particles in a bag of potting soil. They are noticeable but a very minor presence in the overall amount of soil in the bag. In years past, I remember thinking about those little white pieces with some annoyance because I didn’t know what they were or why they were there, only that they seemed less than natural, and definitely not organic. Now I know those chunks are usually one of a few ingredients—either vermiculite, perlite, or pumice rock.
Now, if these three particles were attending a dress event, I’d say pumice might be commented on as having a solid, even staid, character but definitely understated in the appearance department—dull grey, large holes everywhere, irregular in shape—generally reminding me of craters of the moon. But wow, can it have a big impact on how great things can look above ground when used in soil. It solves so many soil issues! I encourage gardeners to experiment with using pumice as they plant and amend their garden soils.
While compost is recommended to improve the porosity and friability of clay soils over time, a compost and pumice combo would be an even better remedy for clay soil. Pumice more effectively improves drainage but adds particles that also help break up the clay—both things that compost helps with as well.This fall, as you begin preparing your beds and planters for winter and next spring, think about dressing up your garden with pumice in addition to compost. Then amend again in the spring with this duo. For troublesome heavy clay soils, it can take repeated diligence over a few years but your soil will reward you for it. Drainage and aeration problems can also be resolved by adding pumice. A couple BONUS “accessories” of pumice are that it retains both moisture and contains and slowly releases trace amounts of minerals plants like and need.
I mentioned buzz words, “natural” and “organic”. Pumice is a rock and as such a mineral. Therefore it is not organic in the true sense that organic means a carbon life form. Rocks aren’t that. But they definitely fit into the definition of being “natural”.
Finally, I can’t help mention I’ll be writing soon about a new addition to our line of soils, one where pumice will play its most significant role in our lineup. You may be able to guess what it is. I’m excited and can’t wait to tell all!
~ Linda Brown