The soil is made of butterfly wings, dinosaur teeth, pumpkin seeds,
lizard skins, and fallen leaves.
Put your hands in the soil and touch yesterday, and all that
will be left of tomorrow shall return so that new life can celebrate this day."
Soil is a wonderful thing. It grows our food, anchors our trees and provides a foundation under our feet. But it sure can be hard to work with when it's not the soft, crumbly loam that many plants prefer. It's amazing that anything grows in some of the soils here in the Santa Cruz mountains. Some folks near Quail Hollow garden in an ancient sea bed of sand and there are others who have such heavy clay in their gardens that you wonder how anything survives.
I used to live up under the trees in Felton where the soil was heavy clay. Now in Bonny Doon, I garden in gritty soil. Both soils have their challenges, but I think clay soil is the hardest to deal with. Soil that doesn’t drain quickly during the winter is especially challenging. Where’s that perfect loam when you need it?
Some soils in Boulder Creek requires a pickax to break up enough to plant. Sound familiar? Although rich in nutrients, clay soil requires compost to provide the environment necessary for beneficial microbes, worms and other critters could do their work and aerate the soil. A thick layer of mulch spread over the soil helps to preserve soil structure and prevent it from packing down again.
There are plants that are tolerant of clay soils but California native plants won’t tolerate standing water for any length of time. They’ll die from either root rot or suffocation as saturated soils prevent oxygen from getting to plant roots. You can plant on a slope where the water is unlikely to saturate the ground around the plant.
Search for native plants that will survive slow draining soils at Calscape - https://calscape.org. Using the Advanced Search Tool you can see which plants tolerate different conditions. Enter your address to find plants for all kinds of sun, moisture and drainage situations. I found 48 plants native to Boulder Creek that tolerate slow drainage on the website. From ceanothus to manzanita to California fuchsia to Douglas iris you’re sure to find plants that look great and perform well.
There are plants from similar environments in other parts of the world that would also do well if you garden in heavy soil. One of my favorite trees for these conditions is the strawberry tree. Also hackberry, ash, gingko and paperbark trees work well also. Shrubs to try to include; flowering quince, bottlebrush, Australian fuchsia, smoke tree, escallonia, pineapple guava, mahonia, osmanthus, Italian buckthorn, elderberry and vitex. Easy perennials for clay soils are yarrow, bergenia, carex grasses, fortnight lily, coreopsis, echinacea, nepeta, salvia, teucrium and verbena to name just a few.
If you're not familiar with some of these plants, it's easy to see what they look like by Googling images. It's what I do to see a plant full grown and not just a line drawing or a close-up of the flower.
So you see, there are plants that will be successful even in heavy, clay soil, you just have to pick the right ones.