Regional Gardening Reports :: National Gardening Association

In the Garden:
Pacific Northwest
November, 2009
Regional Report

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This gnarled cluster of dahlia tubers will eventually be divided. Each division will produce a bushy, multi-stemmed, 6-foot plant loaded with spectacular flowers.

Time to Dig Those Dahlia Tubers

I never met a dahlia I didn't like. They come in all sizes, from miniature plants that look great in borders or containers, to almost bush-like giants, perfect for focal points or as background plants. They come in a wide variety of blossom shapes and shades that range from white to yellow, orange, pink, red, lavender, purple, and bronze, along with variegated and bicolor petals. And in my garden, depending upon the weather, dahlias can bloom right up through Thanksgiving. What's not to like?

Dahlias thrive in sunny beds amended with lots of organic matter. I grow the larger bush-type dahlias by digging a 12-inch-deep hole for each tuber and mixing a handful of bonemeal into the hole. Then I lay the tuber in the hole with the bud facing up, drive a 6-foot-tall stake next to the tuber for future support, backfill with soil, and water well. The bonemeal provides initial nutrients for the young tubers. I side-dress the plants with a granular 6-10-10 fertilizer just before the first blossoms open, to ensure continual flowering. I always space my dahlias 3 feet apart to give each enough room to grow and to encourage air circulation around the plants, which reduces disease problems.

Pinching Dahlias
Some gardeners pinch off side buds to direct growth to one flower bud per stem, which results in fewer but larger flowers. If I were growing for a show, I might be tempted to pinch off buds, too, but I prefer to leave my plants alone and enjoy the multitude of slightly smaller flowers they produce all summer long.

Dahlia Care
Aside from regular, deep watering and occasional deadheading, I've found dahlias to be relatively carefree plants. I like using the flowers for indoor arrangements and have discovered that earwigs like to hide between the flower petals. Rather than have them crawl out onto the dinner table, I'm careful to immerse the entire flower in a bucket of water to dislodge any hitchhiking pests before bringing the flowers indoors.

Storing Tubers in Winter
Even though they are hardy here, I've found the tubers tend to rot if left in our wet soils over the winter months. For this reason I dig my tubers after the first frost, usually in late November. I leave 6 inches of stem to serve as a handle, brush off excess soil, and store tubers in plastic mesh bags in my unheated garage. An alternative storage method I've had good luck with is simply burying the tubers in a bucket filled with vermiculite and storing them in a room protected from freezing temperatures.

Making More Tubers
Tubers can be divided immediately after digging, but I prefer to store them in one big clump, dividing them in spring after the eyes (new growth points) begin to swell. By waiting until spring, I'm assured of cutting them apart in the right place, without injuring the dormant eyes. It's also easier to know which side faces up. Some of the stored tubers look plump and some look dehydrated. The plump ones will be planted first, in the choicest garden spots, followed by their wrinkled relatives, placed in an out-of-the-way garden plot, just in case they don't survive and need to be replaced midseason.

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