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Corydalis

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Corydalis

'China Blue'

Photo © Scott Zona
You may confuse corydalis plants with bleeding hearts, as they both exhibit similar ferny foliage, dangling flowers, and a penchant for shade. However, gardeners have a much wider color selection with corydalis flowers, including the hard-to-find true blue shade.

Latin Name:

The genus corydalis includes approximately 400 plants in the poppy family.

Common Names:

Fumewort refers to the long ago practice of burning corydalis root and inhaling the smoke to clear the mind. We now know that corydalis has toxic properties which can cause convulsions even in small amounts.

Zone:

Hardiness can vary from zones 3-9 according to the cultivar, but many of the most popular varieties only thrive in zones 6-8, disliking both extreme heat and cold.

Size:

10 inches to three feet

Exposure:

Corydalis plants need partial to full shade.

Bloom Period:

Corydalis plants are often advertised as having a bloom cycle that lasts from spring until fall, but this only occurs under optimal growing conditions. Typically, corydalis blooms in May and June, but enters dormancy when summer temperatures begin to soar. In regions with cool, moist summers, corydalis plants may continue to rebloom sporadically throughout the growing season.

Description:

The deeply lobed fern-like foliage of corydalis plants is all the more handsome on cultivars with chartreuse or burgundy-tinged leaves. The tubular blooms of blue, white, pink, purple, and yellow are attractive to hummingbirds.

Planting:

Corydalis plants like the consistent moisture found in many woodland gardens, but they don’t appreciate heavy soils or boggy conditions. Raised beds amended with organic matter like compost or humus will give your corydalis plant a good start. Even planting the corydalis a few inches above grade can improve drainage enough to ensure plant survival.

Maintenance:

Keep your corydalis plants moist, and provide them with an inch of water throughout their dormant season. The plants like regular light feedings, which you can accomplish with weekly applications of compost or manure tea. If you wish to propagate the plants, you can divide them after blooming and before dormancy sets in. It is possible to grow corydalis from seed, but the plants are slow to mature to blooming size and are vulnerable to damping off in the first season.

Pests and Diseases:

Corydalis plants are susceptible to the usual moisture and shade loving slugs and snails, which you can control with bait or traps. Aphids are sometimes a problem in the spring on emerging shoots. Heat and drought stressed plants can attract spider mites.

Corydalis plants that don’t have adequate spacing in the garden may be affected by downy mildew. Plant rust can infect corydalis growing beside walls or buildings, where breezes can’t carry away fungal spores.

Design Tips:

The small size and delicate appearance of corydalis plants is used to best effect along borders and paths in the garden. Plant corydalis with other woodland plants that like moist soil and good drainage, like hostas, columbine, or foam flower. If corydalis plants tend to experience summer dormancy in your area, interplant them with a flower with summer interest, such as lobelia or ligularia. You can also plant them under a hydrangea, which will be filling out and preparing to bloom just as the corydalis show is finished.

Varieties:

  • Blackberry Wine: Purple flowers are very fragrant.
  • Blue Heron: Large blooms, red stems, and a sweet fragrance
  • Blue Panda: It’s hard to find a more brilliant blue flower for the shade garden than this.
  • China Blue: Ethereal sky blue blossoms make the summer dormancy worth it.
  • Corydalis solida: This species is worth growing for its extreme hardiness, down to zone 3. Expect pink, purple, or white flowers on 10-inch plants.
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