Sunday, September 23, 2007

Erosion control

It's because the driveway in the back of our house goes like this:

that there's a bit of an erosion problem at the bottom of the drive.

Access to the back driveway is by means of a blind alley, and on the other side of the alley, the ground slopes steeply down into the neighbor's yard. Winter rains go sluicing down the drive and can tear up the slope, which the downhill neighbors keep barkdusted and free of weeds, so there's nothing to hold the slope together except some photinia bushes. The neighbor kids go running up and down the thin strip of bare dirt that technically belongs to the people on the side of us, but the neighbors don't take care of it, and then they go down the steep barkdusted slope, tearing furrows in the already threatened banks. Their experiments in using a hose full blast to carve canyons into the slope didn't help any, either. After I carefully raked the dirt back into place they kinda got the hint that maybe that wasn't a good idea.

I'd placed a row of rocks along the edge of the paving, trying to divert some of the water, but I'm not sure how effective it's been. So I took stronger measures this weekend. After picking up the rocks, I dug a trench along the edge of the pavement and the top of the slope, piled some of the dirt on the slope side of the trench, and mixed the rest with some compost and steer manure to increase the organic content of the red-clay-and-rock mix that serves as soil in this neighborhood. Then I set the rocks against the small ridge I'd raised, making in effect an very narrow "rain garden" -- or rather, a runoff garden. Here 'tis, freshly dug:

Since our monsoon season is late October through the end of June or so, I planted some native spring-blooming damp-meadow plants, specifically Sidalcea (Checker mallow) and Camas, which I picked up at the fall sale at Wallace Hansen Gardens. I know where I can collect Camas seeds in the spring, too, so I'll sow the plot with seeds later. Since the slope bakes in the summer, I ordered some native Goldenrod and some Zinnia grandiflora, both western prairie plants that do well in dry areas and tolerate clay. I just ordered a few from High Country Gardens to try out. If they can tolerate damp winters, they should flourish in the dry summers. All of these plants are butterfly plants, so if they colonize, I may start getting a healthy population of butterflies around here.

As for the bare dirt slope, I wanted to plant that with something that would hold the slope together, but wouldn't need much care, since it's an awkward place to get a hose into. I also wanted something good for birds or beneficial insects. My Red Hot Poker plants needed thinning, so as I was pulling out big, fat corms I thought, "Well, why not these?" They tolerate shade pretty well, they propagate easily, they exist on little water all summer, they're green in the winter, and the blossoms feed hummingbirds and finches. I collected a bucketfull of healthy corms, used my mattock to dig holes in the compacted soil on the slope, and planted the whole bank in Red Hot Pokers. If I'd thought of that sooner, I'd have tried ordering some fall-blooming ones. Oh, well, these were free. I gave the slope a thorough soaking with a sprinkler while I went inside and cleaned out the guinea pig cage, then lightly mulched the slope with the used shavings.

Now to go talk to the kid next door about the problems of erosion...

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