November in southwestern Ontario means frosts, the first snowfall, and not much left flowering in the garden. In my garden there is one plant – Capnoides sempervirens – that looks wonderfully delicate, but those looks are deceiving. This tough little drought tolerant plant is one of the last to keep blooming – some years I have seen it flowering even after being buried by the first snowfall for several days.
This month’s Plant of the Month features Pale Corydalis (aka Rock Harlequin), a plant that Native Plant Gardening author Lorraine Johnson includes in her Dec 22, 2021 blog entitled “Ghost Plants”. These are plants that, in her words “are difficult to find at nurseries but that would be fabulous additions to gardens and, I’m sure, snapped up by gardeners if they were commercially available” (https://lorrainejohnson.ca/blog). I heartily agree – especially for this one.
Common Name: Pale Corydalis
Scientific Name: Capnoides sempervirens
Family: Fumariaceae (Fumitory Family)
Alternate Common Names: Colic Weed, Harlequin Corydalis, Harlequin Flower, Pale Fumewort, Pink Corydalis, Pink and Yellow Corydalis, Rock Harlequin, Tall Corydalis
Plant description: Pale corydalis is a biennial, producing a basal rosette of leaves during its first year of growth. These leaves are compound in groups of 3-5 with each individual leaflet being deeply cleft into 2-3 parts. These are further divided into 2-3 narrow, rounded segments. Leaves have a blue-green waxy appearance. During its second year of growth, it sends up many branching, erect, hairless, blue-green stems from its basal rosette. Lower leaves are stalked while upper leaves become increasingly stalkless as they ascend. Stems terminate with clusters of dangling, tubular flowers that each measure 1.5cm long. They are somewhat flattened with varying shades of pink tubes and yellow lips at the end of the tubes. Each flower has a pair of teardrop shaped sepals clasping it. Flowers give way to long, narrow seed pods that split open when ripe to reveal tiny black seeds.
In the Garden: Pale corydalis is a unique looking plant with lacy foliage and captivating pink and yellow flowers. It is valued by gardeners for its ease of growth in tough, dry, rocky sites and for its long bloom time. As a biennial, it will only live for two years so expect it to persist in your garden via self-seeding. It is an excellent addition to just about any garden, but is especially effective in the rock garden.
Exposure: full sun to part shade
Soil Type: poor, dry, gravelly soil
Height: 80 cm
Spread: 10 cm
Bloom Period: May to freeze-up
Colour: pink and yellow
Fragrant (Y/N): N
Showy Fruit (Y/N): N
Cut Flower (Y/N): Y
Pests: may be affected by the Macrosiphum corydalis aphid, but other than that is virtually disease and pest free.
Natural Habitat: dry woods, rocky ledges and recent clearings, often growing in areas disturbed by fire
Wildlife value: Long tongued bees, particularly bumblebees, are pollinators and the seeds have an elaiosome (food package) which ants take back to their nest, and thus help to distribute. The nectar rich flowers are also often visited by Skipper butterflies.
Butterfly Larva Host Plant For: none
USDA Hardiness Zone: 2-10
Propagation: Easy to start from seed, no treatment is necessary if the seeds are collected and sown early in the summer. These will produce a rosette by fall and bloom the next year. Seeds collected in the fall, or kept over winter, should be cold-moist stratified for 30 days. These spring sown seeds will flower the following year.
Additional Info: Formerly known as Corydalis sempervirens, it was recently changed to Capnoides sempervirens, and is the only species in the genus Capnoides. This tough little flower will withstand harsh conditions, but does not fare well with a lot of competition. Because of its propensity to self seed, some people find it to be weedy but its delicate flowers and blue-green foliage are welcome anywhere they want to be in my gardens. This species is classified as Endangered in Indiana and Ohio.