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Delphinium Species


Current Activities:

Updated 07/08/08

Species Grown in 2004  
Group 1 European Species

D. staphisagria, D. requienii, D. balcanicum

Group 2 North American Species

D. trolliifolium D. nuttallii D. burkei

D. leucophaeum, D. nuttallianum

D. uliginosum, D. variegatum

Group 3 Species in cultivation

D. venulosum

Group 4 Asiatic Species

D. brunonianum, D. ceratophorum,

D. semibarbatum, D. stapeliosmum,

D. vestitum

In these pages we look at some wild delphiniums that we have attempted to grow with varying degrees of success. Our experience is that species not already in cultivation usually do not have the characteristics required for garden-worthy plants.

Incorrect identifications of both seeds and plants is a common problem facing anyone who wishes to grow species.

Growing delphinium species is a purely 'fun' activity, presenting huge challenges in finding the right conditions for seed germination and plant growth. Sometimes the flowers can be rewarding but most often they are not. It is always interesting to see the different forms that delphiniums can take and the ways they are adapted to cope with widely varying environments.

Current Activities

Delphinium Species in 2008

Cold weather in December 2007with some severe overnight frosts followed by much warmer conditions in the new year provided ideal conditions for dormant delphiniums to start into growth and for seeds to germinate. The ground around a plant of D. causcasicum, for example, was liberally dotted with freshly germinated self-sown seedlings but slugs soon removed these tasty morsels. Seeds of D. oreophilum sown last year germinated in the spring but the seedlings have made very little growth. This species belongs in a frustrating group which includes some American larkspurs from desert environments that never seem to develop beyond the first year seedling stage and it is difficult to know how to treat them.

It was particularly pleasing to find that nearly all seedlings of the black-flowered species, D. triste, survived the winter and grew flowering stems. The strange and very hairy flowers opened during late May and June, with a few further stems of flowers appearing in July. The most disappointing thing was that seed set was very poor and from ten plants only two seeds developed to maturity!

Several other species that have become long term residents in our borders flowered well during June and July. The Hospital Canyon Larkspur from California, D. californicum Ssp. interius had a large mound of foliage in February and survived severe frosts and the plants went on to produce several long spikes reaching 2m tall. The fascinating little flowers are very attractive to bumble bees and made an interesting foil to the equally curious flowers of the massive self-sown plants of D. requienii. Both these delphiniums are prolific seed producers.

Plants of the yellow-flowered D. semibarbatum developed flower stems but weather conditions in June were unfavourable and it seemed possible that the flowers would never open. However, after spraying with insecticide to control spider mites and a fungicide against mildew, the flowers finally opened in late July after a hot dry spell and are now having to survive strong winds and heavy rain.

Another delphinium from sowings of items from the AGS 06/07 list last year, was #2257, which produced extensively branched dwarf plants that have intense deep blue flowers with exceptionally long spurs on very long pedicels. The architecture of the stem branches is rather unusual with the pedicels emerging almost at 90 degrees to the stem, as seen in the picture below. The mature plants have many of these branched stems with the initial stems growing upright but later branches spread out almost horizontally to produce an attractive broad mound of flowers.

The identity of this species is uncertain. In the AGS List item 2257 was said to be D. glareosum, a species from western America that is closely related to D. bicolor. The germination characteristics were not those I would expect for these species and the general character of the plant seems to have more in common with species from Asia. Further investigation of the identity of this attractive delphinium is required.

Delphinium species in 2007

While we already have a rather large collection of assorted delphinium species in the ground and in pots of assorted size, there are so many species of delphinium with interesting features that the seed lists of the Alpine Garden Society and American wildflower specialists are an irresistable temptation. Seeds of two species from the AGS list, D. kumaonense and D. oreophilum, were tried again because they have proved unwilling to grow to flower. D. oreophilum did not germinate but D. kumaonense germinated during late April. The seedlings have cotyledons fused to a single stem, as for American species with tuberous roots and they developed very little before becoming dormant. An un-identified species, AGS-2276, has yielded interesting tiny seedlings (seen below) with very small hairy leaves that suggest they may originate from a high alpine location.

A number of seedlings were raised from seed said to be of D. oxysepalum, which is a dwarf species from the Tatra/West Carpathian mountains of Poland. The general features of the plants and the flowers were as expected but one plant had a clear white eye in the dark blue flowers and another developed some flowers with 13 sepals (semi-double). This suggests that these plants were hybrids.

A single seedling of an annual delphinium from Turkey, D. peregrinum, was raised from seed received from P. Olsson. This is interesting in having leaves tapering into the stalk, in the same way as for the two other European annual species grown previously. Development and flowering of the plant is described in more detail below. Plants of D. triste were raised from seeds from another contact in Sweden but these showed no sign of flowering. It is hoped that the plants will survive the coming winter and produce their black flowers in 2008. From three different sowings of D. staphisagria, one batch suddenly produced five dramatically large seedlings, seen on the right below, after drying out and being then re-wetted by thunderstorm rain. These developed steadily and began to flower in early October. It is fascinating to see the flowers again, ten years after our last success, and it would be nice to know how to reproduce the sequence of drying and re-wetting that led to germination.

Species grown in pots during 2006 were kept dry thoughout the autumn and winter. Plants of the wild-collected form of D. nudicaule started into growth very early and flowered well in April. Most other species remained dry until late April before pots were wetted to stimulate the dormant root systems into growth. Unfortunately a fairly high proportion of the plants produced no growth. Plants of D. leucophaeum produced only a few flowers. However 8 plants of D. variegatum soon developed new leaves and flowered well in July, as seen in the right hand picture below.

Of the wild delphiniums in our borders, the two plants of D. californicum s.sp. interius flowered well among a group of plants of D. requienii. The weather did not suit D. requienii and the foliage and flowers were ruined by the heavy rains. Other American species that flowered well were D. hesperium, (the Western larkspur seen below) and D. glaucum. Despite also being known as the 'Tall' or 'Giant' larkspur, the florets of the form of D. glaucum in our garden seem tiny and insignificant compared to those of some Eurasian delphiniums, such as D. speciosum, which again this year produced a lovely bloom of beautiful bell flowers, seen below. Another species that flowered well was D. maackianum, with its colourful mixture of reddish purple bracts and stems, greyish hairy leaves and deep violet blue flowers. As usual, spraying with systemic fungicide was required to control mildew. The weather conditions did not suit the yellow flowers of D.semibarbatum but the truly dwarf plants of D. cashmerianum have seldom been without a cluster of flowers right through to mid-October.

Perhaps the most fascinating aspect of the species grown from seed this year has been comparison of the flowers of a plant identified at the RHS Garden, Wisley, as Consolida orientalis with those of the lone seedling of D. peregrinum. The dissected leaves of the former suggested that it was an annual larkspur and growing the plants in pots did not work well since most died after suffering root loss. However, the pinkish purple colour of the first flowers was stunning. Taking apart the components of this annual larkspur flower revealed how it differs from a delphinium flower. The five large sepals, with the topmost one having a spur sheathing the nectary, are similar to those of most true delphiniums. The nectary is a single unit with forward pointing lobes, which corresponds to the eye of a delphinium floret that includes two upper petals with spurs forming the nectary and another pair of petals or 'honey leaves' that surround the anthers. The side lobes of the nectary have a curious ear-like structure and their tips fold across the anthers. The inner surface of the upper lobes is streaked with deeper colour. These features presumably attract and guide pollinating insects and the result of their activity was that a flower produces a single seedpod which grows to about 1.5cm in length.

D. peregrinum is itself also an annual flower but the plant differs from typical garden delphiniums in several respects. The first few leaves were like those of D. balcanicum, another annual species described in Group 1. As the stem grows and branches, the leaves become reduced to slender wispy bracts. When the tiny flower buds start to develop, the almost leafless stems look similar to the flower stem of a grass as the feathery plumes start to break out. It is not surprising that one of the common names for this delphinium is 'Rush larkspur'. The flowers have an upward pointing spur about 1cm or more long but the forward pointing sepals and petals are very unusual. The four purplish-blue lower sepals are cupped to form a spoon in which the anthers rest and the pair of lower petals are like inky-blue paddles on thin stalks projecting outwards above the anthers. The most curious feature is the pair of upper petals since each has a side lobe extending downwards and coloured bright yellow in the throat of the nectary. Held together by the sheathing sepal spur, this pair of petals closely resembles the nectary of C. orientalis. As the sepals are less than 1cm long, a magnifying glass was useful to examine the flower! However, pollination of a flower results in the production of a cluster of three seedpods, which is characteristic of true delphiniums. Unfortunately the seed pods have a tendency to rot rather than ripen in the present wet conditions.

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