Plant of the Month

July 2004

Delphinium

by Helen Dillon

Delphinium 'Perlmutterbaum' © Bill O'Sullivan

I keep threatening to give up the large hybrid delphiniums. Without doubt they are one of the more glamorous members of the buttercup family, but troublesome to grow. You must feed, protect young shoots from slugs, thin out overcrowded shoots, mulch, give special extra cans of water, stake and readjust your staking continuously. And then, just as their glorious blue spires of bloom are reaching their zenith of beauty, along comes one of those late June gales...

We still have one (cultivar name forgotten) ordered thirty-two years ago from Blackmore and Langdon's stand at Chelsea Flower Show. And very good it is, too, as is one that we've always called Kitty's Delphinium after Kitty Reardon (the wonderful grower in North Dublin). But I've recently been introduced to some of the cultivars bred by Karl Foerster (1874-1970) in Germany. The first, 'Perlmutterbaum', was given to me by Finlay Colley, having been grown by his mother for fifty years or more. The slender flower spikes are lovely clear blue with black middles. 'Berghimmel', recently acquired, is an exquisite pale turquoise, and one of the first Foerster hybrids, which were released from the mid-1920's right up to his death in 1970.

Delphinium ordered 32 years ago from Blackmore and Langdon (cultivar name forgotten) © Bill O'Sullivan

Apparently Foerster didn't believe in hand-pollination - all his plants in the trial beds were from open-pollinated seed. He grew many thousands of plants and his selection method was to stride through the delphinium field with a terrified garden boy at his heel, beheading all those plants he considered trash, bellowing 'Away with it! The good is the enemy of the best!' Promising plants were labelled 'worthy of observation' and grown on for between five and eight years, before being deemed worthy of general release. His breeding goals were: beauty of flower; freedom from disease (especially powdery mildew); strong, slender spikes that do not require staking; and sound perenniality. I consider the Foerster hybrids terrific plants - neat, sturdy and madly pretty. I'm on the lookout for more.

Some time ago, at one of the RHS Shows in London, I met some dignitaries of The Delphinium Society. I asked what the best method was of propagating them. I was told that you should root basal cuttings (not with hollow stems) in neat Perlite, using small pots. The pots should stand constantly in small pot saucers filled with shallow water until the cuttings are rooted. We use more of the same saucers filled with cheap beer to surround the delphiniums in early spring when the slugs are about to do their damnedest. Although we prepare the planting holes for delphiniums well, using old manure and garden compost, it is recommended not to over-fertilize, so as not to produce weak and floppy growth.

Positioning your delphiniums is important: they need sun and moisture in the growing season, so choose a spot not overshadowed by trees. You need to be able to get at the plants, for all the little attentions they need during the season - I find that the back of the border is too far away. If you don't want all the bother of growing delphiniums, aconitums are a wonderful substitute for slug-free, stake-free gardening (especially 'Stainless Steel, a delectable powdery blue). They belong to old-fashioned, slow gardening, with their troublesome demands, but for me they are the epitome of early summer.

I am indebted to Tom Fischer, Editor, Horticulture Magazine, for the information on Karl Foerster. (Try GOOGLE for more information).

Kitty's Delphinium © Bill O'Sullivan

Contributor

Helen Dillon is a garden writer, lecturer, and passionate gardener who has transformed her own town garden in Dublin, Ireland, into a spectacular series of small gardens filled with an extraordinary collection of plants. She is the author of Garden Artistry: The Secrets of Designing and Planting a Small Garden; The Flower Garden: A Practical Guide to Planning and Planting; Helen Dillon on Gardening; and co-editor of In an Irish Garden.

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