Corydalis Porcelain Blue

Corydalis Porcelain Blue (Corydalis flexuosa 'Porcelain Blue') brings a true sky blue to shaded ground, which is rare. It is a compact woodland perennial at about 30cm tall and wide, carrying slender tubular blue flowers above ferny blue green foliage through spring. Plant it where you walk past it, because the colour reads best close up.

Why you'll love it

• Genuine blue flowers. Clear porcelain blue blooms through spring, a colour almost nothing else offers for a shaded bed.
• A shade plant that actually flowers. It comes from woodland country, so it performs in the dappled light under trees where most flowering perennials sulk.
• Fine ferny foliage. Finely divided blue green leaves hold interest between flushes and contrast well with broader leaved shade plants.
• Frost hardy and humidity tolerant. It handles cold winters and muggy summers, which is an unusual pairing in one perennial.

Where it works best

Borders and mass planting. Plant 25cm apart for a drift of blue in shade, about sixteen plants per square metre. A group of nine or more reads far better than plants scattered singly through a bed.

Rockeries and shaded steps. It suits a cool pocket in a rockery or the base of a retaining wall, where the soil stays moist and the light is filtered.

Pots and containers. A wide, shallow pot in a shaded courtyard keeps it at eye level and lets you control the soil, which matters on heavy ground.

Growing Corydalis Porcelain Blue in Australia

Position and climate. Dappled shade, or morning sun with afternoon protection. Full sun scorches the foliage within a week. This is a cool temperate and warm temperate plant, frost hardy but not one for hot, dry, exposed beds.

Soil. Cool, humus rich soil that holds moisture and still drains. Work leaf mould or compost through the bed before planting and mulch lightly. Heavy clay that stays wet over winter will rot the crown.

Water and feed. Keep the soil evenly moist through spring while the plant is in active growth, then ease back as it slows. A light balanced fertiliser as growth begins in late winter is all it needs.

Pruning and dormancy. There is nothing to prune beyond spent flower stems. In warmer gardens the foliage yellows and vanishes by midsummer, which is dormancy rather than death.

What to expect when it arrives

It is grown as tube stock and as 140mm plants in packs of ten. Tubes are small and best planted in autumn or early spring straight into prepared soil. The 140mm plants are the practical choice if you want a border to look filled in its first season.

Soft leaved perennials travel less comfortably than woody plants, so slight wilting on arrival is normal. Plant promptly, water in well and give them a fortnight of shade. Delivered Australia wide, with delivery from $29.95. Every plant carries our 30 day healthy plant guarantee.

Plant care guides and related reading

• See the full range of plants for full shade.
• Companion ideas in our guide to ground cover plants for shade.
• Browse other rockery plants for cool pockets.
• More ideas in perennial plants for a cottage garden.

Common questions

My plant disappeared over summer. Is it dead?

Almost certainly not. In warm climates it goes dormant once the heat arrives and returns when temperatures drop. Label the spot, keep the soil lightly moist and wait rather than replanting over it.

Will it grow in a hot or tropical garden?

No. It is suited to cool temperate and warm temperate gardens with a real winter. In hot climates it spends most of the year dormant and rarely flowers well enough to justify the space.

Is it safe around cats and dogs?

No. The foliage and roots contain alkaloids that are toxic if eaten, so keep it out of reach in a garden with pets that chew plants, or choose a different shade perennial.