Cathy Isom explains the chemistry behind raised bed gardening and why you should avoid rock dust in a raised garden bed. That’s coming up on This Land of Ours.
Rock dust, in all its various forms, can be useful in some gardens. But it may not be useful in raised beds.
With raised beds, at best you have 6 to 8 inches of planting medium for plants to grow in. Most of the time, there’s not a whole lot of actual “soil” in that planting medium.
Raised bed or potting mixes include peat moss, compost, and sand or perlite, but not clay or silt. The reason they don’t contain either one is that those things impede drainage and encourage soil compaction.
When you garden in incomplete soil that doesn’t contain all the various inorganic elements like rocks, silt, and clay, you need to garden in a different way than you would in soil. The chemistry of those planting mixes is completely different than natural soil. That’s why when you add rock dust to your mix, your traditional raised bed gardening method becomes less effective.
I’m Cathy Isom…