New! Corydalis flexuosa Hillier™ 'Porcelain Blue'

Latin Name Pronunciation: kor-rid' uh-lis  

The five hundred-plus Corydalis species include annuals, biennials, and tuberous or rhizomatous perennials, mostly from northern temperate regions. Commonly grown perennial species naturally grow in cliffs and on rocky slopes in cool, woodland habitats, making these unfussy plants ideal for woodland rock gardens, stone path edges, and shaded stone walls in areas with cool summers.

Corydalis cheilanthifolia is a freely self-sowing evergreen species with yellow blooms from spring into summer; suited for growing in sun to part shade.

Corydalis flexuosa produces blue flowers in late spring/early summer and goes dormant in summer; prefers humus-rich, well-drained soil.

Corydalis lutea is a rhizomatous, evergreen species with yellow flowers. It self-sows freely in sun to part shade and prefers rocky situations, even self-sowing in stone walls.

Corydalis solida is a tuberous species that goes dormant in summer. Variable flower color in a range of pinks, purples, reds, and white have resulted in numerous named cultivars.

When planting, keep the soil level of potted plants even with the surrounding soil. Plant tuberous varieties at the depth indicated on the plant tag.

Light: All these species grow particularly well in part shade, especially the dappled shade created by deciduous shrubs and trees. Corydalis cheilanthifolia, C. lutea, and C. solida tolerate full sun when given proper woodsy soil and sufficient moisture.

Soil: Corydalis prefers moderately fertile, humus-rich soil that retains moisture, yet has very good drainage. Corydalis solida prefers especially sharp drainage and does well in rock gardens and gravelly areas. Plants are not particular about pH, except at the extremes.

Watering: Plants do not like to dry out, nor will they survive in saturated, heavy soils, or standing water. Once established, water during especially hot, dry weather. Plants in full sun will need more attention to watering than those in shade. Varieties that go dormant in summer should be amply watered in spring but not drenched when dormant.

Fertilizer: These plants are not heavy feeders, so an occasional few handfuls of good quality compost or decomposed leaf mulch around each plant is all they really need. A light application of slow-release granular fertilizer may be applied in early spring if desired, but it is not usually necessary. An organic mulch that decomposes over time will provide sufficient nutrients.

Pests/Diseases: Corydalis is susceptible to root rot in heavy soil. Plants may be bothered by common garden pests (aphids, slugs) if stressed, but are generally easy plants.

Dividing/Transplanting: Very small plants may be dug and transplanted in spring, but mature plants resent being transplanted. Increase plants by allowing them to self-sow, or collect ripe seeds and scatter them where you'd like more plants.

Continuing Care: Cut back dormant plants if you wish, although surrounding perennials often fill in the space and cover declining Corydalis foliage without any effort on the gardener’s part. Sunburned or dried-out plants can be cut back to basal foliage, which often will remain green well into winter. Allow plants to ripen seeds if you wish them to self-sow, or deadhead after blooms have finished if you prefer to limit seedlings.

Companions: Heucheras, Carex pensylvanica, and diminutive species Tulips such as Tulipa tarda and Tulips sylvestris make fine companions.