Colorado gardeners can choose this spring from five new plants adapted to the Rocky Mountain region’s harsh climate, thanks to a joint project between Colorado State University and the Denver Botanic Gardens. The new varieties mark the first plants introduced in retail stores as part of Plant Select, a trademarked program that works in conjunction with nurseries and garden centers to identify, evaluate and introduce plants best-suited for climates in the Rocky Mountain and Plains states.
This year’s specimens include shrubs that produce fragrant pink flowers or white blooms and red berries; a spreading ground cover with cobalt blue flowers; an exotic plant that adds bronze- orange blossoms to borders; and a foliage plant that produces large leaves resembling elephant ears. Gardening enthusiasts may recognize these plants by their common names: sunset hyssop, silver sage, Carol Mackie Daphne, Alleghany viburnum and Turkish Veronica.
Plants introduced at retailers this spring were selected from rare landscape specimens, seedling populations and other sources several years ago, then tested extensively in trials at the Denver Botanic Gardens and at Colorado State. Plants that passed muster were tested at other sites across the region and evaluated on how easily they propagated and adapted to the climate as well as their ornamental features, said Jim Klett, professor in the department of horticulture and landscape architecture at Colorado State and a Plant Select coordinator.
"Part of the difficulty for gardening enthusiasts is finding plants that can take intense exposure to sun, adapt to a wide range of soils and don’t require too much water," Klett said. "We have identified many plants suitable to our environment that are rarely seen in retail stores and we are now in the process of making the best candidates available to gardening enthusiasts."
Since its inception, the Plant Select program has identified more than 70 possible new plants for introduction to Colorado and other states with similar climates, Klett said. The program aims to introduce about five new plants to the buying public each year. Eventually, the program hopes to release plants bred and selected specifically for features that make them suitable in Colorado’s climate.
"Plant Select provides a formal mechanism for an informal practice that has become an important tradition in gardening: that of exchanging and promoting the best plants among friends," said Richard H. Daley, executive director of Denver Botanic Gardens.
New plants that meet the Plant Select criteria are identified with one of three product designations: endorsed, introduced and original plants. Plants with the endorsed label are species that have grown in the region for years but have not gained much recognition and are available only through some specialty nurseries. Introduced plants are those discovered by program researchers as ideal additions to gardens and landscapes. Plants with the original designation are hybrids of other plants resulting from extensive research and testing.
All specimens being released this year can be seen at the Denver Botanic Gardens and at Colorado State. Plants debuting at retail stores this year include: * Sunset hyssop (Agastache rupestris)–An exotic plant that has silvery leaves with unusual bronze-orange flowers produced over an extended period in the late summer. It is tolerant of a wide range of soils and seems to thrive in extreme heat and sun. * Silver sage (Salvia argentea)–A member of the mint family, this unusual foliage plant produces large leaves, sometimes a foot or more in length. The leaves are shaped like elephant ears and covered with a dense coat of silver fur. Silver sage grows in either full sun or partial shade and tolerates most soil types and various amounts of water. * Carol Mackie Daphne (Daphne x burkwoodii ‘Carol Mackie’)– This plant prefers more shade, but will tolerate a wide range of soils and is tolerant of the higher alkaline content present in Colorado soils. The plant blooms with intensely fragrant flowers in late March or early April and continues to bloom sporadically throughout the summer months. * Alleghany viburnum (Viburnum x rhytidophylloides ‘Alleghany’)– This plant is a hybrid produced by the U.S. National Arboretum. It has nearly evergreen leaves and doesn’t need a lot of water to thrive. It holds its leaves into the winter after turning purple. Flowers appear in late spring, followed by reddish-black fruit. * Turkish Veronica (Veronica liwanensis)–This sturdy ground cover produces waxy, teardrop-shaped leaves that take on a purple hue in hot sun. This hardy plant requires little water after it is established. Cobalt blue flowers cover the leaves from April to June.
For information on where to purchase these plants, call Panayoti Kelaidis at the Denver Botanic Gardens, (303) 370-8054; or Jim Klett in the department of horticulture and landscape architecture, (970) 491-7179.