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North American Delphinium Species

D. variegatum

A guide to stages in seedling development

D. variegatum the 'Royal Larkspur', is found only in California. It is a common plant of grassland and open oak woodland in the foothills of the Coast Range, Cascade Ranges and Sierra Nevada, plants at times colouring foothills. It is short-growing, with flower stems from 15 - 50cm tall bearing royal blue or purple-blue flowers in April/May that can be exceptionally large relative to the size of the plant.

This species was grown from seed supplied by Northwest Native Seeds collected from plants growing in grassland on heavy rocky clay soil in the inner Northern Coast ranges of Lake County, California, about 100miles north of San Francisco. The tiny seeds differ from the dark brown seeds of familiar garden delphiniums in having a white outer coat. They were sown in late January on the surface of peat-based compost in a 9cm pot and lightly covered with compost and a layer of grit. The pot was left outdoors exposed to the weather but protected from birds and mice by wire mesh. Germination began in early March. Seedlings were very small compared to those of most delphiniums but had the familiar form with a pair of narrow seed leaves on separate stalks and their first true leaf grew from the point where the cotyledon stalks joined the root, as seen in the pictures below. This is characteristic of delphiniums with a fibrous root rather than the tuberous roots of many species from the USA. Seedlings were pricked out into individual pots in late April.

The plants grew slowly, developing a rosette of small but extensively divided leaves with relatively long stalks. Both leaves and stalks are covered in hairs. The plants remained small, hardly extending beyond the rim of their 9cm pots even in early August, as seen in the right hand picture above. Yellowing of the leaves suggested that most were likely to die or go dormant, as most did, rather than to continue growing. Torrential rain associated with a thunderstorm then brought about a miraculous transformation in the surviving plants. Within a few days, two plants suddenly had stems with a cluster of tiny flower buds pushing up from the base. By the end of August these provided a taste of Californian spring, as these plants were in flower with 8 or more large, flat florets held on slender but stiff stems almost 30cm (1ft) tall.

After flowering, plants become dormant. Some have been kept under glass so that compost in the pots dries out, while others have been kept in the open where they are subject to rainfall throughout summer and autumn. Survival of the plants has been fairly good and examination of the plants as they start into growth in early spring (or even in mid-winter) shows that the new flower stems develop from the top of a thickened root, as seen on the right above.

Repotting the plants when new growth first appeared did not cause problems and the plants develop quickly to flower in Spring. In 2006 when weather conditions in the Spring were unfavourable for plant growth, flowering extended into June.The multiple stems of plants in their third season then provided a fine display of flowers followed by well-filled seed pods. The flowers ranged from a few good pure blues but most had extensive purple colouration on the tips of sepals.

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