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There is no exact science to gardening, but there is something that can help gardeners make good plant selections for their landscapes.


Established in 1999, the Oklahoma Proven plant evaluation and marketing program has selected a tree, shrub, perennial and annual that have been proven to tolerate Oklahoma’s difficult environmental conditions. These plants are selected to help gardeners have a successful experience in the garden.


The selections for 2020 include American hornbeam (tree), red yucca (shrub), golden variegated sweet flag (perennial) and Brazilian verbena (annual).


The American hornbeam is a slow-growing, understory tree with an attractive globular form and typically grows to a maximum of 35 feet tall. It produces flowers as separate male and female catkins, with the female catkins giving way to distinctive clusters of winged nutlets. During the summer months, the leaves are a deep green that turn shades of yellow, orange and red in the fall. It grows well in full sun or light shade and prefers well-drained soils. The European hornbeam is very similar to the American species, which also is available. Both have columnar or fastigiate forms available and can be used as a street or lawn tree.


Despite its name, the red yucca isn’t a yucca. It produces soft, yucca-like evergreen leaves and bears showy, coral-colored, tubular flowers on arching, wand-like pink stems. This shrub adds vibrant color throughout the year with plum-colored leaves in the winter and blue-green leaves during other times of the year. The flowers will attract hummingbirds and deer may browse the foliage. Choose a spot to plant that has full sun. Red yucca is drought-resistant and prefers dry soils with excellent drainage.


Golden variegated sweet flag is native to the wetland areas of China, Japan, Korea, India, Thailand, Myanmar and the Philippines. It is a dwarf plant featuring iris-like tufts of narrow, grass-like, variegated leaf blades that are striped with yellow and green. It’s easily grown in average, medium to wet soils in full sun to part shade. It also does well in both boggy conditions and consistently moist garden soils. Be sure the soil never dries out.


The last of the new 2020 selections is the Brazilian verbena, which is a rapidly growing, clump-forming tender perennial that grows as an annual in Oklahoma, with clusters of tiny rose-violet flowers. If grown in a sheltered location with southern exposure, it can survive mild winters. Even if the plant doesn’t survive the winter, it typically remains in gardens for a number of years through self-seeding. Although the plant doesn’t have serious insect or disease problems, keep an eye out for powdery mildew. Brazilian verbena is heat and drought resistant, attracts butterflies and hummingbirds and makes a great cut flower. Improved cultivars include Little One, Meteor Shower® or Lollipop.


While the Oklahoma Proven plants have been selected to withstand environmental stress, please keep in mind all plants need special attention during the establishment phase or during periods of environmental extremes.


More information about Oklahoma Proven is available online at Oklahoma Proven.

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