Corydalis calycosa

Perhaps no other colour attracts so much attention like blue. Reason being that blue pigment used to be rare and expensive, and in some cultures the wealth of a family would be assessed by the number of blue ornaments and objects in the house. Its natural sources were indigo (plant) and various minerals, especially lapis azuli. Cobalt salt was another one and the method to achieve it was known already to ancient Romans and Egyptians, yet its real fame came from old China when during the reign of the Tang Dynasty (7th - 10th century) cobalt blue was frequently used on several types of wares, especially their true transparent porcelain which still today is a sought-after collectible. When it comes to plants, we all know that true blue flowers are in minority, so we are thankful for each of them which shows some blue tint. Such as corydalis whose flowers come in several shades ranging from sky blue, brilliant blue, to cobalt blue.

Corydalis calycosa is a beautiful perennial with blue flowers. Its originates in central China, more precisely in the Sichuan province. Although the province's climate mostly belongs to the subtropical monsoon belt, the central and northern parts have snow-capped mountains and even the Dagu Glacier. This perennial was born right on the border between this subarctic anomaly and the subtropics which makes it well suited for a happy life even in our climate.

Corydalis calycosa is very similar to c. flexuosa or c. elata. Its advantage, however, is a very dense growth and a stronger habit with an extended flowering period. From about mid-June are formed upright racemes composed of unusually shaped, narrowly elongated, tubular flowers with a wide end. Their outer colour ranges from cold cobalt blue to warm deep violet. The throat is almost white.

The flowers top about 40 cm tall stems, which arch slightly at the sides of the clump, but are not pendulous - they just make a wide, relaxed V-shape. The main flowering flush lasts 3-6 weeks, depending on the age of the plant and the amount of nutrients in the soil. Deciduous leaves are fresh green above and pale blue green below, tri-ternate with rounded lobes.

Corydalis is a perennial from the forests of China. It likes partly shaded or shaded but not too dark locations. It will cope with partial or filtered sun if the ground is kept evenly moist and the plant is protected during the hottest hours of the day. It is quite picky about soil type as we need to imitate its natural habitat (woodland margin or a moist semi-shaded meadow): fresh, free-draining but moist, fertile soil, never waterlogged, always cool. Hardy to about -27 °C (USDA zone 5b).

Last update: 21-06-2023