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Delphinium Species 3. Species in Cultivation

 

D.venulosum ?

This is a little known annual species of delphinium that is endemic to Turkey. There are several other rather similar annual species from the Mediterranean region including D. balcanicum from Greece and D. verdunense from France.

We would not have grown this species from choice because we prefer to concentrate on perennial delphiniums. However, the seed is offered by Suttons Seed Ltd under the variety name 'Rhapsody in Blue' with a catalogue entry listing it as a perennial. The following article was a report for the 1999 Autumn Bulletin of the Delphinium Society of our experience in growing this delphinium.

 

First attempts with Suttons 'Rhapsody in Blue'

by David Bassett

'Rhapsody in Blue' is a delphinium seed strain being strongly promoted by Suttons as "Splendid for garden or floral arrangements" and packets of seed are widely available at garden centres. It is not easy to tell from the picture in the catalogue and on the seed packet what sort of delphinium it is, although once the plants flower you realise the picture is a fair representation.

Following instructions on the packet, I sowed the seed in late February in moist compost and kept the pot indoors at 18 - 21C (65 - 70F) alongside pots in which hand-pollinated delphinium seed had been sown. The seed is extremely small, more like that of annuals such as antirrhinums than normal garden delphiniums, and I failed to sow the seeds thinly enough. Germination took about two weeks but then damping-off soon killed most of the seedlings. The seedlings are tiny with very fragile thread-like stems and are difficult to prick-out. With a second batch sown later, I transferred clumps of seedlings directly from the seed tray into the ground and these survived transplanting quite well. [Examination of the seed under a hand lens shows that they are approximately 1mm in diameter and nearly spherical but with a pronounced circular depression at one end. The surface has a series of ridges or rings of scales centred on the pit at the end. This might actually be a continuous spiral ridge runing round the seed from one end to the other. The seeds are thus very similar to those of D. balcanicum and D. verdunense]

Once in the ground, the first batch of seedlings grew strongly, with feathery leaves looking like those of an annual larkspur. [The leaves are unlike most cultivated delphiniums, being cuneate with a 'winged' petiole] In fact the plants reminded me of consolida regalis 'Sky Blue'. As the plants approached flowering at the end of July, they had developed a very bushy, branched habit of thin wiry stems no more than 1 - 2 mm in diameter. One plant, for example, had 13 branches from the main stem, each carrying 6 further branches with 5 lateral stems terminating in a group of about 5 - 10 flower buds. This degree of branching is quite exceptional, even when compared with that of a seedling of D. belladonna (Steichen Strain), which had 10 branches but only two sub-laterals on each. While the latter plant might produce just over 200 individual florets, 'Rhapsody in Blue' plants could each produce well over 2000 florets! [Prolific flower and seed production is a characteristic feature of annual delphinium species and distinguishes them from perennial species]

The flowers are a uniform deep violet-blue (near RHS Colour Chart violet-blue group 89C) with the colour being like that of old-fashioned blue-black fountain pen ink. Each floret is just finger nail size and a terminal group of ten flowers is no more than 10 cm long. As can be seen from the picture above which includes a scale in cm, these are very small flowers, even by the standards of most species delphiniums that we have grown.

Extensive branching did not produce the colourful display that might be expected. This is partly because florets are so small and partly a consequence of the growth habit, with the terminal racemes of branches, laterals and sub-lateral shoots developing in sequence. Flowering also stimulates laterals from lower down the stem to grow past the bloom and bury the flowers in a mass of stems. As a result, three weeks after the f'irst flowers opened, my group of plants still appeared to be mainly green stems and buds with relatively few open flowers. By then it formed a mound 70 cm high that covered an area 90 cm x 80 cm.

Small flowers are not necessarily a disadvantage for an effective border plant, as demonstrated by the salvia verticillata growing alongside, which was far more attractive to bees than the delphinium. Suttons' claims of the garden value of 'Rhapsody in Blue' are not very convincing. In view of the plant structure, I also fail to understand why they recommend it as an ideal flower for cutting.

According to the seed packet, 'Rhapsody in Blue' is D. yunnanense, which was first described in 1893 by A. Franchet and originates from Yunnan and Tibet. There are significant differences between the plants I grew and Franchet's description of D. yunnanense quoted by E. Wilde, particularly in the petals forming the eye of the flower. The two petals within the spur should be light brown but in the flowers grown these petals were violet blue with a pronounced downwards extension enclosing the stamens. The lower petals should be bifid with two lobes at the tip, whereas these were actually square and undivided with no sign at all of hairs forming a beard. D. yunnanense is also said to have a "slightly-branched stem", not extensive branching. I am thus sceptical whether 'Rhapsody in Blue' is D. yunnanense but a detailed comparison of the plants with herbarium material and Flora descriptions would be needed to check this properly.

Additional Comments

Plant material was submitted to botanists at the Royal Horticultural Society's Garden at Wisley, who identified this delphinium as D. venulosum and indicated that this Turkish endemic is an annual.

All the plants grown died after flowering and examination of the roots confirmed that the plant structure was typical of annuals. Only one self sown seedling was found in the following year so it seems unlikely that this delphinium would readily become a weed in our garden!

The identity of the delphinium being sold as 'Rhapsody in Blue' was taken up with Suttons Seeds but, apart from polite correspondence with their customer relations department, they were not prepared to disclose anything about the source of the seed. Futhermore, two years later this delphinium is still being marketed as perennial.

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