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Originally published Thursday, May 22, 2014 at 6:27 AM

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Optimal care for Corydalis and tree peonies

Garden writer Ciscoe Morris gives tips on the spring-blooming perennial Corydalis and long-lived tree peonies.

Special to The Seattle Times

Gardening Events

Ciscoe’s Picks

An Evening of Wine & Artisan Chocolates at Christianson’s Nursery: A benefit for the new La Conner Regional Library building project, 7-9 p.m. May 30. Attendees may shop at the nursery from 5-9 p.m., and John Christianson will lead a tour of the nursery at 6 p.m. 15806 Best Road, Mount Vernon; $25, 21 and over (

‘Your Beautiful Dry Summer Garden’ seminar: 10-11 a.m. May 31. Laura Matter of Seattle Tilth and program director for the Garden Hotline will explain which plants thrive during dry weather without intensive supplemental watering. 9701 15th Ave. N.W., Seattle; free (

‘Get RainWise’ workshop in Ballard: 1-2:30 p.m. May 31. Learn about RainWise rebates for installing rain gardens and cisterns on your property. 6512 12th Ave. N.W., Seattle; free, registration required (


In the Garden

Blue-flowering Corydalis, related to poppies, is among the most attractive of spring-blooming perennials. The botanical name means crested lark and refers to the birdlike appearance of the attractive flowers that appear en masse above ferny foliage.

Among the easiest to grow is the variety ‘Pere David.’ It forms large colonies covered with multitudes of bright-blue flowers that appear in March and often keep on blooming through June. ‘Rainier Blue’ is shockingly beautiful, with electric-blue flowers that stand out in the shady garden from April through June. The queen of the clan has to be Corydalis curviflora Var. rosthornii ‘Blue Heron.’ The wonderfully fragrant sapphire-blue flowers glow like jewels above attractive, blue-green, finely dissected foliage.

Corydalis are easy to grow as long as they are planted in rich, moist yet well-drained soil in brightly lit shade, and fertilized with organic flower food right when the plants begin blooming in the spring. Soon after the flowers fade, the leaves often become tattered, moldy and unattractive. Keep your Corydalis looking great by cutting the stems down to about one-eighth inch from the ground immediately after flowering is over. As long as the soil remains moist, the foliage will grow back looking fresh and attractive. Unfortunately, the plant won’t bloom again until the following spring, but the ferny foliage will remain a nice addition to your woodland garden for the rest of summer.

Plant tree peonies deep

It’s not surprising that tree peonies are the national flower of China. The magnificent flowers can be as big as dinner plates, and their unusual form adds beauty and structure in a mixed border. Best of all, tree peonies can be amazingly long-lived. There are reports of tree peonies living for more than two centuries in China. Of course, if you want your tree peony to live to a ripe old age, it’s important to plant and care for it properly.

For starters, plant your tree peonies differently from your herbaceous peonies (the ones that die back to the ground in fall). Herbaceous peonies won’t tend to bloom unless they are planted no deeper than they came out of the pot. Tree peonies, on the other hand, should be planted considerably deeper because they are grafted on herbaceous peony roots. The herbaceous roots are there only to give the tree peony stems time to root before the herbaceous roots die out. Therefore, tree peonies should be planted so the graft is 4 to 6 inches below the soil surface; otherwise, the herbaceous rootstock will survive and an endless stream of herbaceous peony suckers will grow into your tree peony.

Tree peonies resent competition and should be planted in an open, uncrowded location in full sun and well-drained soil. Mix half a handful of bone meal as well as a cup of organic flower food into the planting hole. Right after planting, and every April afterward, work in a cup of alfalfa meal around the drip line to increase blooming. Choose carefully when deciding where to plant your tree peony. Once established, they resent transplanting. Then be patient because it can easily take three to five years before one finally begins to flower. Considering that you’ll get to enjoy blossoms every year for the next 200, that doesn’t seem too long to wait.

Ciscoe Morris: “Gardening With Ciscoe” airs at 10 a.m. Saturdays on KING 5.

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About Ciscoe Morris

Ciscoe Morris' column runs Thursdays. His show "Gardening with Ciscoe" airs at 10 a.m. on Saturdays on King 5.

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