Flowers seed ERYNGIUM alpinum 'Blue Star Alpine Sea Holly
Beds, borders, cottage gardens. Single specimen or small groupings of at least 3-6 plants or massed. Dryish, sun-baked beds. Excellent long-lasting cut flower that also dries well.
|Sowing to Germination:||4 - 8 weeks|
|Germination to Transplant:||4 - 8 weeks|
|Transplanting to Potting:||6 - 10 weeks|
Eryngium alpinum, commonly called alpine sea holly, is a somewhat coarse, stiffly-branched, taprooted, rosette-forming herbaceous perennial that typically grows on upright stems to 25-32” tall with a spread to 18” wide. It is native to subalpine rocky areas and moist pastures up to 6500’ in elevation in central and southeastern Europe.
Strong, solitary, upright stems are topped from mid-summer into fall (July-early October) with single, cone-shaped, thistle-like, blue flower heads (to 2” long) densely packed with tiny blue flowers. Each flower head is subtended by a collar of 12-18 ornamentally attractive, bristly, finely-divided, somewhat soft-to-the-touch blue bracts which extend outward and upward from the base of the flower head. Plants feature ovate, spiny-toothed, heart-shaped basal leaves (to 3-6” long) and palmately-divided 3-lobed upper stem leaves. Foliage is green near the base of the plant, but upper leaves, upper stems, flowers and flower bracts are bluish.
|Container Size(s):||1-2 plugs per 11/12 cm (4 1/2") / 2-3 plugs per 15 cm (6")|
|Vernalization:||A prudent recommendation would be to provide 6-12 weeks at an average daily temperature of 40°F (5°C). Exposure to cold may not be necessary for flowering but might improve quality.|
|Forcing:||There has been no research, but an obvious place to experiment - following vernalization - would be raising daytime temperatures to 60° - 65°F (15° - 17°C). Provide 16 hours of continuous lighting. During the short days of winter, provide a night interruption lighting of 4 hours between 10:00 p.m. and 2:00 a.m. Some later flowering species can be forced in 14 - 16 weeks and perhaps sooner at warmer temperatures. Further experiments are warranted.|
|Fertilizer:||Light (100-150 ppm)|