Hurrah! ….it is a frost! The dahlias are all dead!
Surtees, Handley Cross 1843
Alas the poor dahlia has been something of a garden misfit since it first departed the New World for the Old. Beloved by the Aztecs as a medicinal plant, the dahlia left its native Mexico for the Royal Gardens at Madrid in 1789, imported not for its flowers – which in the original species were a rather mundane yellow – but because it was thought its fleshy tuber might make a new and useful vegetable. Judged “edible, but not agreeable”, the tubers never made it to the table. But the “brilliant, barbaric flowers” of dahlia pinnata did manage to attract the attention of various European hybridizers, who thought the six-foot high plant might hold some promise as an exotic annual. Crosses were made in France and Spain, and Empress Josephine planted some of the first new cultivars in her gardens at Malmaison. Several of these varieties were imported to England after the Napoleonic Wars, where by 1830, they had become all the rage. D. pinnata was rapidly transformed through cross-breeding from a fairly simple, large, flowering plant into an almost unimaginable number of different varieties in all sizes, shapes and colors.
The dahlia’s popularity did not come without controversy however. Considered by many to be garish, as early as 1823 English nurseryman Thomas Hogg considered them “too large for the small flower-garden” and “best adapted to fill up the vacancies in the ornamental shrubberies.” Some people felt even that usage too much, and dahlias, whose big, loud flowers are always hard to ignore, were one of the first casualties when garden fashion changed at the turn of the century away from brilliantly colored exotics to a more subdued, perennial palette. Dahlias have always had their ardent admirers though, and hundreds of new introductions continued to be made over the years. Today, dahlias have regained much of their popularity: Thousands of varieties exist, divided into 18 classifications according to flower type, ranging from human sized plants with 8 inch peony like flowers, to small single varieties only six inches high. These days, there really is a dahlia for almost every garden style and setting.
I’ve always enjoyed dahlias in my garden, in moderation, and try to include some in the borders each year. Their culture is really quite simple. Purchase tubers (or young plants) now at the nursery, and plant in rich soil. (Tubers may be started early indoors, planted in pots about 6″ deep.) Do pay attention to individual growth requirements however: dahlias very wildly in habit, and you need to make sure that you choose a variety which will be the right height for your site. After planting, mulch, keep well watered, fertilized, and you’ll soon see them take off – dahlias grow quickly and aren’t especially troubled by pests. Occasionally diseases such as mosaic virus can be an issue. Quick removal of infected plants can generally keep the problem from spreading.
Although many people treat their dahlias as annuals, they are actually tender perennials, hardy to zone 10, and particularly nice specimens are often worth saving. There are many different ways to over-winter dahlias, and I have read some complicated methods offered by dahlia aficionados. I’ve had good luck with the following: Simply cut the plant back to one foot above the ground just prior to hard frost, and carefully raise the tubers. Carefully remove any attached dirt, (you may need to wash them with a hose) as well as any rotted or injured parts of the tuber. Let dry for a few hours. Prune the stems back to the tubers, label, and place in loose plastic bags, with a few holes punched in for air circulation. Store the tubers just like you would potatoes: in a cool, dry place at 35-40 degrees. (The veggie drawer in the refrigerator is ideal, which is why in my house, between the dahlias, seed potatoes and other bulbs, rarely sees a an edible.) Replant in the garden when all danger of frost is past.