Pacific Northwest

October, 2008
Regional Report

Books

Rock Garden Plants: A Color Encyclopedia
Rock Garden Plants: A Color Encyclopedia, by Baldassare Mineo (Timber Press, 1999; $59.95), is a truly inspiring book by the owner of Siskiyou Rare Plant Nursery in Medford, Oregon. Over 1,300 plants are described, from herbaceous to shrubby, succulent to woody, along with their growing requirements. There are lists of plants for specific situations, from dry sun to moist shade, and suggested collections of plants for specific rock garden themes. The photos are spectacular!

Clever Gardening Technique

Digging and Storing Dahlias
Because they're hardy only to USDA Hardiness Zone 8, dahlia tubers need to be dug up in the fall here in the Pacific Northwest and overwintered in a cool, dark, dry place. A root cellar or unfinished basement is ideal. A garage or a shed will also work, as long as the temperature doesn't drop below freezing and doesn't get too warm, which would cause the tubers to break dormancy prematurely.

Dahlia tubers can be dug up anytime after the first killing frost. Before harvesting my dahlias, I cut the plants off just a little above ground level, rediscovering the identification tag I placed next to the plant back in June. I've been very careful to keep the plants accurately identified so I can arrange them for color and form in my garden.

Digging up dahlia tubers is work, but it's enjoyable. Every time my shovel turns over a bundle of tubers, it's like finding buried treasure. An amazing thing about dahlias is the number of new tubers produced by one plant. Typically, there's a clump of six to eight, each of which will grow into an identical dahlia the following year.

After I dig them up, I tie a tag around the bundle and place the tubers in a heavy-duty paper bag with vermiculite. Though some dahlia growers dust their tubers with a fungicide before storing them, I haven't found this necessary. I fold the top of the bag down loosely to enable air circulation and to prevent disease. I don't let the tubers dry out before storing and I'm not fussy about getting all the dirt off of them. I find they stay nice and plump this way.

Some dahlia growers store tubers in cardboard or wooden boxes, but paper bags work perfectly for me. In addition to tagging the individual stalks, I also group dahlias with similar-sized flowers in the same bags and label the bags accordingly.

Come spring, I take my tubers out of storage and prepare to pot them up for an early start on the new year. I divide the tubers by cutting them apart, off of last year's stalk, being sure there's at least one eye (just like on a potato) up near the stalk end. This year's plant will grow from this eye. If there's no eye on a tuber, I toss it.

Generally, I plant one tuber per pot, or if they're small, perhaps two or three. Pot size isn't important; whatever I have, I use. I fill the pots about two-thirds full of potting soil, set the tubers in place, and fill the pots to the top. A label goes in the pot. The pots are watered regularly for the next two months, and when the tubers start sprouting, I add fertilizer to the water. Then, come mid-May, it's time for planting them out again and another dahlia year is in full swing.

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