Yellow corydalis

Yellow corydalis: how do you recognise it?

Habit

Loose, bushy plant about 30 cm tall and wide, with brittle stems and a short, thick rootstock.

Foliage

Finely divided, fern-like, two to three times pinnate, blue-green; largely evergreen in mild winters.

Flowers

Short racemes of 6–16 yellow, tubular flowers of 1.5–2 cm with a spur, from April to October.

Seed

Black, shiny seeds with a nutritious appendage that attracts ants; this is how the seeds end up in walls and joints.

Roots

Fibrous and brittle with a short, thick rootstock; it moves best as a young plant.

Flowering: April–October · Plants: March–April and September–October · Pruning: July–August

Why grow it?

• Flowers for seven months, from April to October, even in shade and dry soil.
• The fine, blue-green foliage is decorative in its own right and stays largely on the plant in mild winters.
• Grows where little else will: in wall crevices, between stones and in dense shade.
• Bees and bumblebees visit the flowers.
• Fully hardy to about −25 °C and almost indestructible.
• Self-seeds and so fills joints, walls and rocky corners for free.

Yellow corydalis: where does it grow best?

• Any light level will do: sun, half shade or shade. In sun the soil must stay a little moist.
• Any well-drained soil: sand, loam or clay, neutral to chalky. It even grows in the lime mortar of old walls.
• Dry to moderately moist; it tolerates dry shade under trees.
• Ideal in walls, rock gardens, paving cracks and at the foot of a border.
• Allow 30 cm per plant; in fact it takes care of the rest itself.

Light

Sun, partial shade and shade

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

0.3 m tall, 0.3 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Hardy geranium: Blue and pink flowers next to the blue-green foliage.
• Hosta: Large, sturdy leaves in the same half shade.
• Ferns: Fresh green fronds in the same shady corner.
• Lady’s mantle: Soft yellow flowers and foliage in the same half-shaded border.
• Bellflower: Lovely in the same wall, with blue bells above the yellow.

Yellow corydalis: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or in September–October, when the soil is neither frozen nor too wet.
2. Dig a hole as wide as the root ball; do not add extra compost, it likes lean soil.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. For a wall: put young plants into a crevice with a little soil, or sow ripe seed in a joint.
5. Water in straight away and keep the soil lightly moist in the first year.
6. After that it usually needs no watering or care.

Care

Water

In the first year water weekly in dry weather. After that it copes, even in a dry summer.

Feeding

Not needed. It does best in poor, chalky soil.

Cutting back

Cut it back in July–August when it gets untidy or leggy; fresh foliage and a new flush of flowers follow.

Spent flowers

Cut off the racemes to limit self-seeding, or leave a few if you want young plants.

Tidying

In March remove dead leaves and pull up seedlings where you do not want them.

Tip: Put one plant by an old wall or in paving cracks and let it do its thing: it finds its own spots. Pull up young plants where you do not want them, because it can become a nuisance.

Yellow corydalis: when to prune it?

Pruning months: July–August.

When: In July or August, when the plant has become untidy.

How:

• Cut the whole plant back to about 5–10 cm above the ground: fresh foliage appears within a few weeks.
• Cut off faded racemes to limit self-seeding.
• In March remove dead or damaged leaves.

Caution: All parts contain alkaloids and are poisonous if eaten. Keep children, dogs, cats and grazing animals away from the plant, and take care when weeding or tidying.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Collect ripe seed in June–August and sow it straight away in a tray or directly into a wall joint: fresh seed germinates best. It germinates in autumn or the following spring. Often it simply self-seeds.

Moving seedlings

Move small seedlings in spring or autumn, with as much root and soil as possible; large plants transplant badly because the rootstock snaps.

Yellow corydalis: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy, to about −25 °C: no protection is needed in Belgian winters.
• The foliage stays largely green in mild winters; in severe winters it partly dies back and the plant grows again in spring.
• In a pot: use a free-draining mix with coarse sand and put the pot in a sheltered spot so that it does not stay wet.

Diseases and pests

• Too many seedlings: It seeds itself into walls, joints and borders. Pull up young plants and cut off the seed pods before they ripen.
• Slugs: Holes in young leaves in spring. Collect them in the evening and clear hiding places.
• Downy mildew: Yellow patches on the leaves and grey fuzz underneath in damp weather. Cut off affected leaves and leave air between plants.
• Untidy plant: After months of flowering it gets long and bare. Cut it back in July–August and it will grow back fresh.

Through the year

• March: Remove dead leaves. Plant.
• April: Flowering begins. Plant.
• May: Flowering. Pull up seedlings where needed.
• June: Flowering. Collect ripe seed and sow.
• July: Cut back if untidy.
• August: New flowers after cutting back.
• September: Plant and move. Sow.
• October: Last flowers. Check seedlings.

Edible and useful

Not edible. All parts of these relatives of bleeding heart are poisonous: they contain alkaloids that cause vomiting, stomach ache and, in larger amounts, trembling and seizures if swallowed. In grazing livestock, especially cattle and sheep, poisoning by related species is known: do not plant them in or beside a field, and never throw plant remains into a field or pen. Keep small children, dogs and cats away from the plant, and wear gloves when working with it, as the sap can irritate the skin. They self-seed easily, in walls and between paving too: pull out unwanted seedlings wearing gloves. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• It is native to the southern Alps and has naturalised across western Europe on old walls.
• The name Pseudofumaria means ‘false fumitory’ and points to its relationship with the fumitories (Fumaria).
• The genus Corydalis takes its name from the Greek word for the crested lark: the flower’s spur resembles the bird’s hind claw.