Regional Gardening Reports :: National Gardening Association

In the Garden:
May, 2011
Regional Report

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This 'Stellar' dogwood flower is composed of four creamy white bracts surrounding a tight flower cluster.

Demystifying Spring-Flowering Dogwoods

This May, Angela's 'Stellar Pink' hybrid dogwood is blooming creamy white. We chose it in 2002 for its pink flowers and resistance to anthracnose. Angela already had a white flowering dogwood. For its first two years, 'Stellar Pink' bloomed the color of cream swirling in milk. "You sold me the wrong cultivar," I complained to the nursery owner. He explained that as a hybrid -- Cornus florida x Cornus kousa -- it would find its true flower color with time.

In 2005 and years following, the bracts were pale pink. Bracts are the colorful, three- to four-inch petal-like forms that surround the small, tight flower cluster. Though it's not botanically correct, we commonly call this whole structure the "flower" -- as we do with poinsettias. Last spring 'Stellar Pink' took a turn and abandoned its blush.

Rutgers University researcher Elwin Orton developed the Stellar Series -- 'Pink', 'Aurora', 'Constellation', 'Celestial', 'Stardust', 'Ruth Ellen' -- to combine the best of our native flowering dogwood and the Japanese dogwood. These are also known as Cornus x rutgersensis.

Why? In the 1970s native American dogwoods, Cornus florida, were dying from dogwood anthracnose and dogwood borer. The Asian Cornus kousa is hardier and resistant to anthracnose, powdery mildew, and North American insects. Elwin Orton hybridized the two species to make a healthier 'Stellar' variety. He later cross-bred the Kousa dogwood and Cornus nuttalli to make the Jersey Star series, including the robust, white-flowering 'Venus' and 'Starlight'. 'Red Pygmy', a rare dwarf red dogwood tree, is a recent Rutgers release.

Our Native Dogwood
Many of us older gardeners grew up anticipating spring's breathtaking, fragrant white or pink blossoms of Cornus florida -- our native flowering or Virginia dogwood. In April, we'd look for their spreading crowns, with airy tiers of flower covered branches before other tree canopies filled with green leaves. I seem to remember a dogwood or two with both pink AND white flowers.

Cornus florida reaches 20 to 40 feet tall and wide. It flowers best in light shade and is host to the spring azure butterfly. In autumn, shiny red berries cluster above scarlet foliage -- before the birds devour them. It prefers acid soil (pH <6.8), part shade, and moist soil. Besides pink-bracted 'Stokes Pink', there are red flowered cultivars including 'Royal Beauty', 'Sweetwater Red', 'Cherokee Chief', 'Cherokee Sunset', and 'Cherokee Brave'.

Japanese Flowering Dogwood
Cornus kousa, the Japanese flowering dogwood, is upright and vase-shaped. It's taller than broad -- 20 to 30 feet tall, 15 to 20 feet wide. Its white or pink bracts open in May and June for four to six weeks. The floral array is similar to a doublefile viburnum.
In autumn, its plump, knobby green fruits ripen to delicious pink/ red raspberry-like sweets. Cornus kousa resists anthracnose and other diseases and pests. It tolerates alkaline soil. Cornus kousa var. chinensis 'Milky Way' is the most sought cultivar for its heavy flower and fruit production.

Mulch soil under the dogwood canopy to conserve moisture.
Water new transplants often and deeply during summer's hot, dry spells for three years after planting to reduce leaf scorch.

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