Amsonia hubrichtii
Potting of amsonia. Grow Amsonia (Blue Star) in fertile, well-drained soil in sun or light-shade. Leave them alone after planting. Propagation of amsonia. Increase these plants by dividing them in the spring, by softwood cuttings in the summer, or by sowing seeds in the fall.
Family: Apocynaceae.
Origin: USA: Arkansas and Oklahoma.
Special features: A perennial with extraordinary textural beauty exploding with beautiful golden-yellow fall colour.
Colour: Star-shaped, sky-blue flowers.
Natural Flowering Period: May - July.
Winter Hardiness Zones: Z4-9.
Growth Habit: Bushy.
Foliage: Very narrow (thread-like) linear-shaped leaves.
Height with Flower: 90 cm.
Spacing between Plants: 100 cm.
Soil Requirement: Any well-drained soil, pH 5.8 - 6.8.
Location: Full sun.
Use: Plant together in large groups for a spectacular fall show. Lovely with ornamental grasses like Panicum virgatum.
Specialities: A durable insect and disease resistant perennial.
Cultural Tips: Grams per 1000 seeds: 11,111. Seeds per Gram: 90.
Seeding Recommendation: 30 g / 1000 plants.
Sowing Rate: 2-3 seeds per cell.
Plug tray recommended size(s): 72, 128.
Germination: These perennial seeds germinate very irregularly over a long period. Lower temperatues of less than +5°C  are very effective. Seed trays should not be discarded prematurely. Constant moisture must be maintained. Do not leave in direct sunlight.
Scheduling.
Best Sowing Date: November - March.
Sowing to Germination: 3 - 10 weeks.
Germination to Transplant: 4 - 8 weeks.
Transplanting to salable Plant: 6 - 10 weeks.
Cutting-Back at Transplanting: Cut-back once to keep more compact. 
Growing On: Container Size(s): 1-2 plugs per 11/12 cm; 2-3 plugs per 15 cm.
Vernalization: There is no current research on vernalization but a prudent recommendation for any perennial would be 6-12 weeks (a few might need 15 weeks!) at an average daily temperature of 5°C. Exposure to cold may not be necessary for flowering but might improve quality.
Forcing: This species is not a suitable candidate for forcing.
Fertilization: Medium (150-200 ppm).

Amsonia hubrichtii
 

Eng.: Thread-leaf Blue Star, Hubricht's bluestar, Arkansas Blue Star. Suom.: Tuikki. Sven.: Amsonia.