Plant Select is a program to identify, promote and distribute little known, but great plants that are successful in Colorado and the Intermountain West. It is a cooperative venture of the Denver Botanic Gardens and Colorado State University, along with many nursery and landscape professionals. The program is more than ten years old and has brought to public view both natives and other well-adapted plants. Several plants are chosen each year and introduced through colorful brochures, the Plant Select web site and through various demonstration gardens, which can be found at www.plantselect.org/demonstrationgardens.
Our nursery, Harlequin’s Gardens, has a demonstration garden of Plant Select plants where we test new introductions. We are not just interested in “Proven Sellers” or in any new and different pretty face; we want plants to be sustainable in Colorado. And fortunately, more and more leaders in horticulture are promoting sustainability. The new CEO at Denver Botanic Gardens, Brian Vogt, recently stated, “We will launch new initiatives to place the Gardens squarely in the midst of a broad movement to develop sustainability for our communities and our planet.” And so in this article, I will present a sampling of Plant Select Stars that have proved their Colorado sustainability in our tests at Harlequin’s Gardens and beyond.
Mojave Sage, Salvia pachyphylla, is a shrub-sized perennial that is a summer star of the xeriscape. The evergreen, silvery leaves contrast with the rosy-purple bracts that surround the blue trumpet flowers. In full bloom the effect is spectacular, and it can flower from June to November. In addition, the aromatic foliage is resistant to deer and rabbits. Although it grows rapidly, it may take 3 years to reach its mature 3’x3′ size. Salvia pachyphylla appreciates full sun and good drainage and is very drought tolerant, once established. Prune back a little in the fall to keep it compact and upright under snow loads. Intense heat is no problem and it is hardy to 5500′.
Penstemon rostriflorus is one of my personal favorites. It is long-lived, tolerates a wide range of conditions and blooms in the summer when we can use some color. The flowers are small, orange-red trumpets on stems that stand 24—36″ high and are very attractive to hummingbirds. I have been growing this penstemon for about 7 years in a harsh, dry location. It is a native of SW Colorado and the US Southwest. Penstemon rostriflorus, sometimes known as Bridges’ Penstemon, is very drought tolerant, but with a little irrigation can bloom from July to October. It is successful up to 7000′ elevation.
One of the 2007 Plant Select winners is “Hot Wings” Tatarian Maple. This well-adapted ornamental maple can be a large shrub or small tree. Its name comes from the brilliant red winged seedpods that color the tree all summer. The Tatarian Maple is a native of SE Europe and Western Asia and was not well known in Colorado until Gary Epstein from Ft.Collins Nursery, started growing it as an alternative to Ginnala Maple. Acer ginnala often suffers from yellowing chlorosis because of our alkaline soils, but Tatarian Maple does not. Trialing many seed-grown specimens over several years, Gary noticed that one tree had very colorful samaras, or winged seed pods. With the support of Plant Select, he patented this tree as “Hot Wings”. It grows 15—18′ high and wide, possibly larger in many years, and is quite drought tolerant. For good performance, water deeply every 3 or 4 weeks. Its fall color is also attractive, beginning red, then becoming orange and yellow. Colorado really needed a small ornamental tree that is drought tolerant, colorful and tolerant of our alkaline soils.
There are not many large ornamental grasses that are successful in low-water conditions, but Giant Sacaton, Sporobolus wrightii, is a Southwestern native of dry, sandy ground and rocky slopes. It will achieve its 7′ height even when irrigated only once or twice a-month. The blades grow to 3—4′ high and wide, and the branched feathery seed heads mature to a golden color, “blooming” late summer to fall. It will grow faster with moderate watering and performs well in loose or clay soils. It is reported to tolerate partial shade, but I have not seen it flowering well in part shade. Leave the dry grass and seeds for winter ornament, and cut it to 4—6″ in February or March. This non-suckering clump grass has been a dramatic beauty in my xeriscape garden for the last 6 years. It can be grown up to 7000′ elevation.
Another Plant Select star in my xeriscape garden is Eriogonum ‘Kannah Creek’. This is an especially attractive form of our native Sulphur Flower. It grows 6—15″ high and 12—24″ wide. The foliage is lower and tighter than many Eriogonum umbellatum plants and the all-winter mahogany foliage color is fabulous. The yellow flowers bloom in May/June, forming clusters on thin stems, and they age to an orangey-brown that remains colorful and attractive long after they dry. ‘Kannah Creek’ Eriogonum will grow in sun or part shade with moderate water or it can thrive very dry in part shade. It is hardy up to 10,000′.
In July when many ornamentals have bloomed and are in various states of decline, recline or stupefied somnolence, it is a great relief to see Ephedra equisitina radiating with vitality and beauty. This unusual Chinese herb has no leaves as we know them, but finely textured thin blue stems that are jointed. This Bluestem Joint Fir flowers inconspicuously, and after 3 or 4 years, begins bearing showy red berries (cones). This plant grows to 4—6′ high and 3—8′ wide, remaining ever-bluegreen. It is extremely drought and heat tolerant and can be grown at elevations to 7000′.
Some other sustainable stars from the Plant Select program are:
Artemisia versicolor ‘Seafoam’
Berlandiera lyrata – Chocolate Flower
Satureja montana ssp illyrica – Purple Winter Savory
Chamaebatiaria millefolium – Fernbush
Prunus besseyi “Pawnee Buttes” – Pawnee Buttes Sandcherry
Salvia daghestanica – Platinum Sage
Lonicera korolkowii ‘Blue Velvet’ – Blue Velvet Honeysuckle
Fallugia paradoxa- Apache Plume
Buddleja alternifolia ‘Argentea’ – Silver Butterfly Bush
Agastache rupestris – Sunset Hyssop
Callirhoe involucrata – Winecups
Diascia integerrima ‘Coral Canyon’ – Coral Canyon Twinspur
Philadelphus lewisii- Lewis Mock Orange
Veronica liwanensis – Turkish Veronica
Penstemon linarioides var. coloradoensis ‘Silverton’– Bluemat Penstemon