Elkhorn Garden and while I stood there dazed before the photos of all the gorgeous blooms, the exhibitor started chatting with me and before I knew it he had walked me through some options and helped me pick out four varieties.
I'll be planting my dahlias this week and here's how it will go. I'm planting them in a bed in my front yard where they'll get full sun. Before planting, I'm going to add some compost and work it into the soil. The tubers don't need to be planted very deep--only about three inches below the soil line--but it's important that the "eyes" of the tuber (where the sprouts will grow from) are facing up. Not every tuber has eyes, or eyes that are easy to spot, anyway. A couple of my tubers have already started to sprout but on the other two, I can't see any eyes. I'm planting them anyway and I'll wait to see if anything sprouts. I'll add a small stake next to each tuber with a label with the cultivar name. Dahlias don't need frequent watering until they start to bloom; then Elkhorn recommends soaking them about every 10 days. Avoid high-nitrogen fertilizers, which will encourage too much green growth. The dahlias should bloom throughout the summer and into fall, until there is a frost.
One of the great things about gardening in a mild climate with sandy soil is that you don't have to go through the tedious process of digging up dahlia tubers each autumn, storing them through the winter, and replanting them in the spring. Because we don't have hard freezes here in the Bay Area, and because the soil drains quickly enough that the tubers aren't likely to rot, I can leave these dahlias in the ground. In a few years I'll need to dig them up and divide them. But until then, they can stay put and it will be one less thing to worry about getting in the ground in the spring. And the guy from Elkhorn Garden gave me a great tip: At the end of the season when I cut the spent bush down to the ground, he recommended leaving a stub of a stem a couple inches above the soil line, then covering it with an overturned pot or saucer. That will prevent rainwater from accumulating in the hollow stem and rotting the tuber, and will also serve as a plant marker so I know to plant around where the dahlia will come back the following spring.