Delphinium Seeds | Blue
LATIN NAME: Delphinium
COMMON NAME: Delphinium
Plant Profile
Blue delphiniums are the backbone of the tall perennial border, bred for a strong, even spike of deeply coloured flowers with a paler or darker bee-shaped centre. Cultivars such as the blue forms of the Pacific and New Millennium series are the result of careful line breeding for colour density and stem strength, and names like ‘Blue Bird’ and ‘King Arthur’ mark the deep, saturated end of the range. Planted in a generous drift rather than a single row, the blue spikes read as a sheet of colour from across the garden, which is why the plant is the classic choice for the back of a mixed border where it can tower without shading its neighbours.
The modern tall blue delphinium is the work of generations of hybridisers, from the early elatum crosses to the Pacific line developed in California and later the New Zealand-bred New Millennium series. Each step pushed the blue deeper and the stem straighter for both garden and florist use, and the flower remains the July birth flower in the old floral calendar. The deep blue cultivars such as ‘Blue Bird’ and ‘King Arthur’ were selected for a bee that reads as near-black at the petal’s heart, a marking that lifts the whole spike and helps bees locate the nectar at the base of the spur.
Blue delphiniums colour most strongly on a sweet, alkaline soil, so work a little garden lime into the bed where the ground trends acid, and set the crown shallow so the stem base stays dry. A firm, well-drained root run matters more than feeding, because the tall spike topples fast if the base sits wet in a still, shaded corner.
Science & Biotechnology
The blue colour comes from delphinidin, an anthocyanin pigment that the plant loads into its petals in high concentration. The compound is named after the genus Delphinium, and the same pigment blues blueberries and cornflowers, so the garden spike is chemically kin to a bowl of summer fruit and a wildfield weed alike.
Uses & Benefits
The same delphinidin that colours the garden spike was traditionally used to make a short-lived blue dye and ink from the crushed petals, a craft echo of the woad and indigo vats of earlier centuries. The colour is fugitive and shifts with the pH of the bath, which is why it never rivaled those staples, but it gives a pretty demonstration of the pigment that named the chemistry.
Every part of the plant carries diterpene alkaloids such as methyllycaconitine, concentrated in the seed and young leaf, and delphinium is toxic if eaten, a real hazard to grazing livestock that meet wild larkspur on rangeland. Gardeners should wear gloves for heavy handling and keep cut stems away from children and pets, as the beauty is not a food.
Growing from Seed
In floristry the blue spike is a staple for summer work, valued because almost nothing else supplies that exact vertical blue, and a row of conditioned stems in deep water will hold its colour through a long wedding weekend.
The large, angled seed wants a cool start that echoes the alpine winter of its wild parents, and a cold spell in the seed tray is the difference between a thin stand and a full one.
Sow on a fine loam-and-sand mix, cover lightly, and keep cool and just moist; fresh seed gives the best stand. Prick out at the second true leaf and move plants on when they show four or five true leaves and stand about fifteen centimetres, handling them by the leaf so the taproot is not checked.
Set the crown shallow in its final spot and feed lightly as the spike forms, watering at the base to keep the foliage dry and so limit mildew. Space the plants so air moves between them, which matters more for blue than for any other colour because the dark petals show disease least yet the leaves suffer most from a still, damp row. After the first spike fades, cut it back to a strong side shoot and the plant often throws a shorter second flowering that carries the border into late summer.
Our Take
I grow blue delphinium as the spine of the early summer border, letting clematis tangutica twine behind and purple foxglove echo the vertical line. A Delphinium delavayi in a contrasting tone fills the rear of the bed.
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