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OKLAHOMA PROVEN!


Oklahoma Proven is a plant promotion program coordinated by faculty in the Department of Horticulture and Landscape Architecture at Oklahoma State University. The goal of the program is to recommend plants well-adapted for use across Oklahoma.

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Collector's Choice for 2014


Seven-son-flower

Heptacodium miconioides

Seven-son-flower is an upright, irregular, loose and open shrub growing 15 to 20’ high. Leaves appear early spring soft green maturing to dark green; very attractive and pest free. Flower buds form in early summer, but do not open until September. Individual flowers are tiny, but fragrant and attract butterflies to the garden. Sepals persist and change green to rose-purple and are as attractive as the flowers. Bark is exfoliating, whitish, to rich brown and green.
Seven-son-flower grows best in moist, well-drained, acid soil, but seems adaptable.

• Exposure: Full sun to part shade
• Soil: Prefers moist, well-drained soil
• Hardiness: USDA Zone 5-8

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Tree for 2014


Desert-willow cultivars

Chilopsis linearis
Desert-willow is not a willow at all, and prefers dry, well-drained soils, compared to true willows, which grow along streams and ponds; in fact, it will not tolerate heavy, wet soils. Because it likes the hotter, drier climates it is an excellent choice for western Oklahoma. Desert-willow grows as a small tree 15’-30’ high and 10’ to 25’ wide. It is a loose, gangly tree favored for its colorful, funnel-shaped flowers that put on their biggest show in early summer, and then bloom sporadically throughout the rest of summer. Flowers can be white, pink, rose, or lavender with purple markings inside and are sweetly fragrant. Foliage is a rich green in summer with no fall color, falling early to reveal the interesting branching structure. Several cultivars exist. Desert-willow makes a great patio or small specimen tree and attracts hummingbirds and other birds.

• Exposure: Full sun
• Soil: Dry, well-drained soils
• Hardiness: USDA Zone 7-9

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Shrub for 2014


Blue Muffin® Viburnum

Viburnum dentatum ‘Christom’

Blue Muffin viburnum is a small, compact version of the native arrowwood viburnum growing about 3’ to 5’ high and just as wide. Blue Muffin prefers moist, well-drained soils, but is adaptable to a wide range of other soils. Established plants are somewhat drought tolerant, have no serious pest problems, and require very little maintenance making them excellent for the urban landscape. As with many viburnums, Blue Muffin offers season-long interest with white spring flowers, dark green summer foliage that turns red and orange in fall, and blue fruits the birds love in late summer/fall. Prune right after flowering, but only if necessary. Grow Blue Muffin as a specimen, in groupings, in shrub borders, as a foundation planting or as a hedge.

• Exposure: Sun, part shade
• Soil: Moist, well-drained
• Hardiness: USDA Zone 3-8

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Perennial for 2014


Switchgrass Cultivars

Panicum virgatum

Switchgrass is native throughout North America and is a dominant species of the tallgrass prairies. It doesn’t mind most soils and actually grows well in wet and dry locations. Full sun is the best exposure for switchgrass, but it will grow in part shade; too much shade or rich soils may result in floppy plants. Switchgrass is a warm-season perennial, growing largely as a bunchgrass 3 to 6 feet tall, but may spread by rhizomes or self-seeding. Switchgrass has an upright, stiff form overall. Flower panicles are open, lacy sprays, with a purplish tint that persist into the winter. Leaf color is generally medium green turning yellow, sometimes with orange tints, in fall; however, several cultivars exist – ‘Heavy Metal’, has metallic-blue foliage, ‘Northwind’ is bluish-green, ‘Shenandoah’ has foliage with dark purple tips, and ‘Cheyenne Sky’ turns wine red. Winter color is tan to beige. Once established, switchgrass is very drought tolerant. It is grown as an accent, in groups or masses and can be effective as a screen. It also works well in native plant gardens, wild gardens, meadows, naturalized areas, as well as rain, water, and bog gardens.

• Exposure: Sun, part shade
• Soil: Tolerates about any soil
• Hardiness: USDA Zone 5-9

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Annual for 2014


Corkscrew Rush

Juncus effusus 'Big Twister'

Corkscrew rush with its uniquely twisted stems, though relatively small (18-24” high and wide), still commands attention in any garden space. The stems curl and spiral creating a tangled mass. Corkscrew rush grows in full sun or part shade and prefers moist soils. Happy even submerged in water, it is perfect for a water garden. Corkscrew Rush also is an excellent accent plant for containers. Though considered hardy to about zone 6, it tends to be more of a tender perennial in our area. Its annual nature may be due to the dry winters and the drastic temperature fluctuations we often experience .

• Exposure: Full sun to part shade
• Soil: Very moist to wet, acidic
• Hardiness: Use as an annual