Bulbous Corydalis: Planting, Growing, and Care

Description and botany

The tuberous corydalis is a perennial plant from the poppy family (formerly Fumariaceae), like the poppy or Bleeding Heart (Dicentra). Corydalis are very close to fumitories, and were previously classified in the Fumariaceae family. The Corydalis genus includes over 500 species. They are native to temperate regions of the Northern Hemisphere, from northern Europe and Asia, mainly China. In their natural habitat, these plants grow primarily in forests, fresh undergrowth, shaded and damp environments, and often in montane meadows.

Some Corydalis have changed families, such as the Solid Corydalis (Corydalis solida) or solid-tubered corydalis. This species has naturalised in France. We distinguish Corydalis solida, which grows from a bulb or more precisely a tuber, from Corydalis flexuosa, which are herbaceous plants spreading via stolons. It is sometimes confused with common fumitory or hollow corydalis, Corydalis cava, to which it is very similar.

This small tuberous perennial plant develops into a bushy clump from a single tuberised root. Its bulb contains nutrient reserves and has no space between its layers, hence its names ‘solida’ and ‘solid-tubered corydalis’. At maturity, it reaches 15 to 20 cm in height with a spread of 20 to 25 cm.

Finely and deeply incised, with a light appearance, the foliage resembles that of maidenhair fern or columbine. The deciduous aerial vegetation completely disappears in winter. In spring, stems with finely divided, petiolate and compound leaves emerge from the soil. They are alternate, divided into 3 narrow, ovate segments. They measure 5 to 8 cm long and display beautiful shades of green, ranging from light grey-green to bluish-green.

Above this lush, finely divided nest of greenery, flowering occurs towards the end of spring, from March to May. The upright flower stems bear clusters of 10 to 20 compact, hermaphroditic flowers at their tips, standing erect above the foliage. The flowers have a slender, elongated, tubular shape, 1 to 2 cm long. They are composed of four fused petals, the lower one equipped with a long, tapered spur reflexed backwards. This crest-like feature is said to have given the plant its vernacular name, “Korydallis” in Greek meaning “crested lark”. The corydalis takes on the appearance of a bush populated by birds. The tube opens into a mouth with 2 lips, revealing a white throat furnished with stamens. Digitate bracts, divided into strips, encircle each flower.

The Solid Corydalis bears delicate purplish-pink flowers in Corydalis solida ‘Purple Bird’, or diaphanous white in ‘White Swallow’, which stand out beautifully against the green foliage, hence its very poetic English nickname ‘White Swallow’.

Corydalis solida ‘Purple Bird’, ‘White Swallow’ and ‘Beth Evans’

After pollination by insects, these inflorescences give way to elongated capsules, up to 2.5 cm long, containing black seeds. The plant tends to self-seed without ever becoming invasive.

When summer arrives, with the first heat, the foliage withers and yellows, the plant goes dormant to protect itself from drought, leaving the bulb dormant underground. It will reappear the following spring.

Main varieties

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Planting the bulbous Corydalis

Where to Plant It?

Extremely hardy down to -23.5°C, the bulbous Corydalis can be grown without difficulty in most of our regions. This small tuberous plant is a perennial of fresh woodlands, appreciating partial shade, or even full shade, or light sun. It dislikes overly hot and scorching exposures and grows easily under deciduous trees, where it does not fear root competition. It requires very well-draining and moderately fertile soil, remaining fresh in spring. It will tolerate a sunny position (except in the South of France) if the soil remains sufficiently moist and cool in summer. Accommodating, it tolerates the presence of lime and clay in the soil. It dislikes summer drought, nor excess water in winter which could cause the bulb to rot.

In the garden, however, avoid planting in large groups, as once summer arrives, the bulbous corydalis often disappears, leaving an unsightly gap in flower beds.

The bulbous corydalis is ideal for dressing up shady areas, such as woodland edges or cool rockeries. It will also thrive in perennial borders or edging, atop walls in partial shade. This plant also performs very well in pots.

When to Plant Bulbous Corydalis?

Planting Corydalis solida bulbs is preferably done in autumn from September to November, outside periods of frost and drought. They will have more time to establish. They can also be planted in February if necessary.

How to Plant It?

The bulbs of bulbous Corydalis are prone to drying out and rotting out of the ground, so they should be planted without delay after purchase.

In the ground

Plant approximately 15 bulbs per m² in perfectly drained soil.

• Loosen the soil
• Dig a hole using a dibber and spread a handful of gravel or pozzolana about two centimetres beneath the bulbs
• Plant at about 3 times the height of the bulb, spacing them about 20 cm apart, ensuring they do not touch
• In heavy soil, improve drainage with gravel or pozzolana
• Cover the bulbs with soil mixed with good-quality compost
• Water generously
• Remember to mark the location of the bulbs with a label or small stake to avoid forgetting them during dormancy

In pots

Bulbous Corydalis grows easily in pots, allowing you to enjoy its lovely early spring flowering on the terrace or balcony.

• Spread a layer of clay pebbles at the bottom of a pot or planter with drainage holes
• Fill with a light, well-draining mix of compost and gravel or pozzolana
• Plant the bulbs, covering them with three times their height in soil
• Water once a week during the growing season, then stop watering in summer during dormancy when the foliage begins to yellow

Corydalis solida

Cultivation and Care of Bulbous Corydalis

Corydalis solida requires little maintenance. In summer, the soil should remain moist: ensure regular watering, especially during hot, dry weather. You can apply a mulch such as flax mulch or ramial chipped wood (RCW) around the base to retain moisture. Stop watering during the summer dormancy period.

In early spring before flowering, spread some well-rotted compost around your corydalis plants to enrich the soil.

During the flowering period, remove faded flowers as they appear to encourage new blooms.

Only cut back the foliage to ground level once it has completely withered, allowing the bulb time to replenish its reserves.

This corydalis is rarely affected by diseases and pests in well-drained soil. Excess moisture can cause bulb rot. However, gastropods may feast on the young foliage in spring. Slug treatment from February onwards is essential. Follow our advice to protect it from slugs and snails. The solid-tubered corydalis can be affected by downy mildew and rust, particularly during prolonged dry spells.

Propagation

The bulbous corydalis tends to self-seed. To obtain new young plants, you can collect the seed from the current year and sow them in autumn. Give them a few days of stratification in the refrigerator. Sow on the surface of a special sowing soil mixed with sand. Water with a fine spray. Place the pots in a bright spot but sheltered from direct sunlight at 15°C and keep the substrate moist. Be patient, germination can sometimes take a while. Transplant into the garden when the seedling reach 5 cm in height.

Pair with

Since Corydalis solida is not bothered by competition from tree or bush roots, in a woodland garden it can be planted beneath deciduous trees alongside ferns, such as Dryopteris or Polystichum with their finely cut foliage, brunneras, Solomon’s seals, and a carpet of periwinkles. The luminous flowering of Dicentra spectabilis and epimediums will make excellent companions.

In a partially shaded rockery, it will thrive alongside Geranium nodosum, heucheras, purple creeping bugle, and campanulas.

It will also be perfect near a water feature and at the base of marginal aquatic plants, such as rodgersias, hostas, ligularias, goat’s beards, and other astilbes that enjoy similar conditions.

It will beautifully accompany a host of spring bulbs like hyacinths, Fritillaria bulbs (Fritillaria meleagris), chionodoxa, cyclamens, ipheions, scillas, or even botanical tulips.

Corydalis solida ‘Beth Evans’ in good company with Chionodoxa lucilliae ‘Alba’ and Scilla sibirica