Hope no one minds me posting this in the two places where the folks with the best shot of knowing the answers might be.
I am planning on adding a small bed (which may expand into a border if it works well) of deer resistant, xeric plants, that prefer a very lean well drained soil.I'm thinking Lavenders and the like. My native soil is a glacial till mix of clay, silt and rock certainly lean, but hardly well drained and not at all easy to dig ( we have bent several small pick-axes trying). I have rather a lot of a very rich compost, loam, and sand mix that I use in my raised beds. What would I best add to that to lower the richness and increase the drainage and in about what proportions? Coarse sand and fine gravel? Or should I just mix something from scratch? I am gardening on the Sammamish Plateau just east of Seattle in US Zone 7, Sunset zone 4. Thanks for your thoughts.
Kyra
How to make poor soil?
NO SAND that will make it worse use something more like pea gravel (coarse gravel) qty depends on size of bed..
Hi Kyra - when I'm putting something like cactus in, I usually add pumice - anything kind of bulky and irregular like that or smallish gravel should help a lot. If your sand is nice sandbox-type stuff, it can actually cake and on occasion mix with other stuff and get really hard.
Good luck, HTH!
Decomposed granite makes the soil well-drained also. I mix it in for some of my native plants that like well-drained soil. Raised beds are good when you're dealing with difficult soil conditions. I have caliche. That stuff can kill more plants than anything else I know about! Raised beds are great!
Kyra - I have lived on the plateau for 20 years - on the SW end of Pine Lake. My soil is variable, depending on where you dig. It tends to drain well, but is exceptionally rich. I have had success with amending the soil - the gravel idea is the best, unless you can raise the level. It has been difficult to grow certain xeric plants - too much foliage, at the expense of flowers. I normally do NOT recommend Cedar Grove compost as I brought in 20+ yds of it years back - but it will work well for most things that require excellent drainage. I mixed it with native soil 1/1, then spent years rebuilding my soil in certain areas. My experience is that excellent drainage with the amount of rain we typically get = nutrient depletion. But again, xeric types should love it. The best to you! K