The Q&A Archives: Dahlias

Question: In California (Zone 8)is it true that you can leave your Dahlias in the ground in the winter? If so what mulch should I use and should I cut back any of the foliage. We just got our first rain today.

Answer: Dahlias grow easily in zones 4-10. In zones 8-10 you can leave the tubers in the ground over the winter (zone 8 with mulch), providing the planting bed has good drainage. In all other zones it is best to dig the tubers up before or just after the first mild frost.

Here's how to grow impressive dahlias: After frost kills the foliage, dig the dahlia tubers, shake off excess soil, and store the tubers in peatmoss or sawdust. The tubers should look like the spokes of a wheel with the original stem in the center. Place the entire group on a layer of peat and place more peat around them. Store your dahlias in a cool, dark location where it remains above freezing during the winter months. In the spring you can divide the tubers. Look for a tiny bud (or eye) on the topmost part of the tuber, closest to the stem. As you cut each tuber away from the old, dried stem, make sure each tuber has a bud. When you're ready to plant, choose a site that gets sunshine all day, and dig a hole about one-foot deep for each tuber, spaced about three feet apart. Mix 1/4 cup of complete fertilizer into the bottom of the hole, add about 4 inches of soil, and drive a 4-5 foot stake into the hole. Then plant each tuber, with the eye pointing toward the stake, and cover it with 3 inches of soil. Water well, and when the tuber sprouts, gradually fill the hole in with soil. Don't completely cover the emerging stem and leaves, but keep building up the level of soil. This method will give your mature dahlia lots of underground support. As the stem grows above soil level, tie it loosely to the stake. Dahlias growing in enriched soil won't need additional fertilizer throughout the season, but should be watered every week during the growing and blooming season. Plan to supply one-inch of water per week to each of your dahlia plants. Following the above guidelines should provide you with healthy, happy dahlias.

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