One of the first things to get me hooked on gardening was an illustration of delphiniums in full bloom. The otherworldly beauty of their soaring flower spires in shades of peacock, sky and electric violet was mesmerising and I coveted them instantly. Too many decades later I feel the same way, except now I know how difficult they are to grow well.
First on this herbaceous perennial’s long list of must-haves is the very best of soils, meaning nothing less than a cool, deep, rich, moisture-retentive but free-draining fertile loam in full sun. Forget trying to grow delphiniums in ground that’s in any way prone to winter wet or summer drought, neither of which they will forgive you for.
Despite the picture-perfect image of their tall blue flower spires taking pride of place in a traditional cottage garden, delphiniums are also not the most convivial of plants and resent being grown in these kinds of crowded conditions. Instead, they need space around their roots and plenty of it.
Delphinium plants must be staked in late spring before they get so tall that it becomes too difficult to do so without resulting in a frustratingly messy, ugly tangle of twine and garden canes
Like teenage boys, they are also forever hungry, demanding regular mulches of well-rotted manure and garden compost along with some sprinkles of a slow-release fertiliser around the base of the plants in spring and then again after the first flush of their astonishing flowers has faded by late June/early July. Liquid foliar feeds during the growing season are also a good idea, while prompt deadheading is needed to keep the show on the road.
If you want them to produce the spectacularly large flower heads that are the stuff of show benches, then it’s also recommended that you use a knife to cut out some of the plant’s young shoots in spring when they are 8-15cm tall, leaving no more than five per plant.
That’s only the half of it. Those long, hollow, brittle flower stems can snap easily in a gusty wind, so delphinium plants must be staked in late spring before they get so tall that it becomes too difficult to do so without resulting in a frustratingly messy, ugly tangle of twine and garden canes. Even then, just one day of heavy rain can leave them looking miserably bedraggled.
And don’t talk to me about pests and diseases. Slugs and snails love them, greedily devouring the succulent shoots of this stately, summer-flowering perennial as they emerge above ground in spring unless you take very careful, very-well-timed precautions. Aphids can be a problem in early summer, and earwigs later in the season when the second flush of blooms appears. Delphiniums can also succumb to powdery mildew when the weather is too dry for their liking and to delphinium black blotch if it’s too wet, occasionally fall victim to various root, stem and crown rots, and are vulnerable to a variety of viruses resulting in stunted growth and deformation and discolouration of the flowers and leaves.
I thought I’d finally hit the jackpot when I succeeded in raising a batch of New Zealand-bred Dowdeswell delphiniums from seed to full and bonny bloom
The potted history of my delphinium journey probably echoes that of many. Repeated early failures to grow them were a result of poor site selection and preparation combined with a lack of vigilance as regards slug and snail damage. In short, I hopefully planted them in a spot that I thought they might like and then promptly forgot all about them until the following spring when they failed to reappear. Determined to do better, I thought I’d finally hit the jackpot when I succeeded in raising a batch of New Zealand-bred Dowdeswell delphiniums from seed to full and bonny bloom. They thrived for several years, thrilling everyone who saw them. I was unapologetically smug until the summer they suddenly sickened and died, leaving me outraged and bereft.
Given all of the above, you might reasonably conclude that it would be quite commonsensical for gardeners to forego delphiniums entirely. But that would be to miss the point, which is that their special beauty aside, delphiniums appeal to our irrational side as well as to our competitive instincts. Presented with a plant that is so undeniably difficult to grow well, we just can’t help scratching the itch to try.
And so I continue to love delphiniums with the same passion that I first felt all those years ago and do my very best to grow them well, cosseting them along by every means necessary. Truth is, nothing comes close to them in terms of the size, stature and brilliance of their flowers as well, of course as their magical range of colours. Blue is very rare in nature, but delphiniums provide it in almost every shade possible from the calico blue of a variety like the award-winning Delphinium Centurion Sky Blue to the ultramarine of Delphinium Faust or the pale ice-blue of Delphinium Balkleid. For this reason, they also make outstanding cut-flowers, adding a flash of brilliance to an arrangement that’s hard to beat. But just don’t say you haven’t been warned.
This Week in the Garden
Regular deadheading is one of the secrets to prolonging the display of flowering annuals, biennials and perennials at this time of year. So is liquid feeding, using a potash-rich feed to encourage the production of new flowers. This is especially true of displays growing in containers and hanging baskets, where plant roots will quickly run out of space and nutrients.
Conversely, don’t deadhead plants if you want them to self-seed around the place. Instead, leave their flowers to fade and allow the seed heads that follow to slowly ripen over the coming weeks before either collecting them or allowing them to spill.
Dates for your Diary: Saturday, July 6th- Sunday, July 7th (11am-6pm), Galway Garden Festival, Claregalway Castle, Claregalway, County Galway, with a wonderful range of specialist plant nurseries, exhibitions of Irish botanical art, and guest speakers Klaus Laitenberger, Jimi Blake, Karen Williams, and Fionnuala Fallon, see galwaygardenfestival.com
