New hydrangea cultivars for landscape gardens

“Ruby Slippers” and “Munchkin” are the latest cultivars released by ARS geneticist Sandy Reed with the U.S. National Arboretum's Floral and Nursery Plants Research Unit's worksite in McMinnville, Tenn. The arboretum is operated by ARS, the principal intramural scientific research agency of the U.S. Department of Agriculture (USDA).

The new cultivars are the first compact forms of Hydrangea quercifolia, a species of hydrangea native to the southeastern United States, to be released by ARS. H. quercifolia is commonly known as oakleaf hydrangea because its leaves resemble those from oak trees. According to Reed, currently available oakleaf hydrangea cultivars are taller than desired for small landscape gardens or, if shorter, don't have good flowering qualities.

Ruby Slippers and Munchkin address both of these issues. The new cultivars are small in stature and have large flower heads that stay upright, even after heavy rains. They grow 3-4 feet tall and 4-5 feet wide after nine years of growth, with flower heads held upright above their leaves, making them particularly suited for use in small residential landscapes. Flowers on Ruby Slippers open white but quickly turn pale pink and deepen into rose, while those on Munchkin open white and gradually turn medium pink. Both plants flower in early summer.

Like other oakleaf hydrangeas, Ruby Slippers and Munchkin can be grown in full sun or light shade and are hardy in USDA zones 5 to 8. They can be used in shrub borders or mass-planted in large areas. The plants have been evaluated by cooperators throughout the United States, and cooperators are currently increasing stock. Reed anticipates the plants will be widely available for sale to consumers in the next year or two.

Nursery crops are a multi-billion dollar industry. Wholesalers in 17 states surveyed by the USDA's National Agricultural Statistics Service grossed $4.65 billion in sales in 2006, the last year for which figures are available. That's an increase of 17 percent from 2003 sales. Deciduous shrubs like the oakleaf hydrangea accounted for 14 percent of the industry's total sales in 2006.

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