USDA Hardiness Zone 6

Plants are known to be cold hardy to at least -10°F.

Other Cold Hardiness categories

Common Name: Blue Avena Grass, blue oat grass

I love ornamental grasses and this grass tops my list. Blueish green evergreen leaves. A cool season clump forming, medium height grass. Treat it as medium water-use for the first year or two. Blue avena grass is not particular about soil, just as long as it’s well drained. After 2-3 years, blue avena grass will put out light tan oat-like plumes.  This grass performs better in afternoon shade.

Common Name: Missouri Evening Primrose, Bigfruit evening-primrose, Ozark Sundrops

Oenothera macrocarpa, and O. missouriensis have been used interchangeably. Native over a wide range including the plains and wooded areas, carries the common name, Missouri evening primrose, bigfruit sundrops and Ozark Sundrops. 

Common Name: Salvia darcyi

The flowers of Salvia darcyi are similar in appearance to Salvia greggii, however the shrub itself is more herbaceous than shrubby. I know of no common name for S. dacryi. Some sources say it is cold hardy to Zone 7, however it thrives in Denver Botanical Garden’s Zone 5. S. darcyi is native to the mountains of Northern Mexico and will do well in amended soil. Hummingbirds love it.

I have it planted in my xeristrip for a number of years. It will flower more vigorously with irrigation everyother week, when needed during hot drought years.

Common Name: Calamint

Calamint, a member of the mint family, sparkles with white/pale lavender flowers in late summer into fall. Solid green foliage emits a pleasing mint fragrance. Attracts bees. Sometimes referred to as lesser calamint. Calamintha nepeta spp nepeta covers itself with light blue flowers.

Common Name: Hyssop, Hummingbird Mint, Licorice Mint

Agastaches are some of the Southwest's showiest natives and one of our native perennials where must breeding and hybridization is being done. Native to slightly higher elevations that 3600 ft., it requires either afternoon shade or medium water-use. It has not been reliable in coming back for me, but it has for others. Well drained soil is a must. Nonetheless, it is easy to be seduced by its masses of blooms and alluring fragrances. Hummingbirds certainly are entranced.

Common Name: Honeysuckle, coral

Another American native vine, evergreen in more southern climates than ours, but cold hardy here. Fragrant and attractive coral flowers in spring and early summer. Attracts birds, butterflies and hummingbirds. Pleasant glossy green leaves. Not invasive. Medium water-use.

Common Name: Alkali sacaton

Alkali sacaton is a perennial warm season bunch grass native to the Southwest. In late summer to fall, airy triangular seed heads wave above the silver green grass blades. Grows in alkali soils, many say in locations where there is moisture nearby, prefering heavy clay soils. It is quite drought tolerant once established, and long lived. It will, of course, grow bigger or smaller depending on water resources.

Common Name: Green Santolina

Green santolina is an evergreen shrub native to the Mediterranean region. Its grass-green color makes it a welcome addition to any landscape. Medium and low water use, cold hardy, sun and heat tolerant, it prefers poorer soil. Aromatic green leaves that resemble those of the cypress. Yellow button flowers in summer.

Common Name: Mat Daisy, Atlas Daisy

Mat daisy is a low growing spring blooming plant. Drought tolerant. Not exactly a groundcover, as the top growth disappears during summer and reemerges as a green basal rosette in fall, getting ready to bloom again in the spring. Blooms late March to May with small white daisy-like flowers that have pink undersides. Forms a compact ground-hugging mat. Will self seed some, but never invasively.

Common Name: Sweet Autumn Clematis

Although usually sold as Clemantis paniculata, it could be C. terniflora. Sweetly fragrant, low water-use vigorous growing vine for great late summer display. Creamy white flowers form silvery seed heads.  Cut back in spring as it blooms on new growth.

Common Name: Hybrid Daylilies

Green sword-like foliage with striking bell or funnel shaped flowers that last only a day. Hundreds of different hybrids and cultivars in a wide range of colors, some early, mid and late summer blooming. Daylilies do better in medium, well-amended soil and a sunny location that enjoys afternoon shade, but they are versatile. Daylily leaves may exhibit alkalinity in clay soil. If this is the case, amend well with organic matter.

Common Name: Silver Blade Missouri Evening Primrose

Gorgeous! Luscious goblet shaped lemon yellow flowers on this native wildflower that also develops elongated seed capsules. The lighter, silvery sheen of the leaves distinguishes the O. macrocarpa var. incana subspecies, and is also an evening to morning bloomer.

Common Name: Furman's Red Autumn Sage, Cherry Sage

If I had to pick my favorite plant, this is it. Long blooming and drought tolerant with only minimal maintenance of late winter cutting back, and maybe a bloom pick-me-up deadheading at mid summer. It will also re seed some so you’ll have more of them the next year. It’s fragrance is light and pleasantly of sage. Salvia greggiis are native to Texas in the Kerrville area. It is my favorite, but not the absolutely perfect plant. The stems are quite brittle and very easily break or snap off, even when you’re carefully weeding around it.

Common Name: Silver Speedwell

Most gardeners’ acquaintance with veronicas is with the Veronica spicatas, ‘Red Fox’, ‘Icicle’, and ‘Sunny Border Blue’; the tall, spiky red, white and blue medium and high water-use veronicas. But consider the low water-use option, V. incana. Deadhead to prolong the blooms and water deeply once a month, once established in well-drained soil. The gray-green leaves should be a give-away by now as to its water requirements.

Common Name: Stansbury cliffrose

Previously known as Cowenia mexicana, it is known today as Purshia stansburyana, also, P. stansburyiana. It is still commonly called a cliffrose. The cliffrose blooms prolifically in May with creamy white to pale yellow fragrant flowers that continue blooming for several weeks. Semi evergreen, it loses it's leaves in colder winters. Upright stems and branches can appear unruly in its growth pattern; small dark green resinous leaves.

Common Name: Big Bend Silverleaf

Big Bend silverleaf is the most cold hardy of the Leucophyllums and has wintered over in Amarillo, Zone 7, for 5 years so far. Possibly cold hardy to Zone 6. It is hard to beat a more attractive summer blooming shrub for small xeric spaces. After summer rainfalls, Big Bend silverleaf, native to the Big Bend National Park area, becomes covered in silver blue flowers that twinkle like jewels among its silvery gray leaves. Hard to find, it's worth searching for.

Common Name: Tansy Aster, Tahoka Daisy

Tansy aster is an annual native to the Southwest and throughout the Plains even into Canada. Fernlike, or tansy-like (tannacetifolia) light green foliage with beautiful aster-like lavender flowers with yellow disks about 1 1/2 to 2 inches across. Blooms from late spring through fall. A once a month watering will keep the blooms coming throughout the summer. It will keep its compact shape in lean, poor soil but will become much larger in well amended soil. Minimal amending is recommended. Tansy aster is another example of our natives plants giving so much, asking so little in return.

Common Name: Giant Sacaton

Giant sacaton is one of the largest bunch grasses native to the Southwest, like alkali sacaton on steroids. Seems to thrive in poor soils with no supplemental irrigation. It will grow even bigger with added moisture. Thick textured grass blades, it will rival pampas grass for size and beauty, although it plumes are near as showy, giant sacaton has a flowing fountain appearance. A warm season grass, it is cold hardy and thrives in sun and heat.

Common Name: Beargrass, Sacahuista

Bear grass is similar in appearance to yucca and clumping grass, but is neither. Usually found growing in high desert areas, along cliffs and rocky slopes. Thin succulent grasslike yellow-green leaves emerge from a trunkless center, are pointed and sharp edged. A plume-like inflorescence with many tiny cream colored flowers emerges early summer. Cold hardy, drought and heat tolerant.

Common Name: Mohave Sage

Beautiful xeric sage with aromatic soft gray green leaves, mostly evergreen. Summer to fall blooming with mauve/purple sticky but fragrant flowers. Takes a few years to reach mature height. Requires good drainage and dry soil in the winter. A Plant Select® Plant. Native to California and will grow in the High Desert regions. Cold hardy to Zone 5 and quite heat tolerant.

Common Name: Columbine

Many Aquilegia’s are native to the U.S. Golden columbine, Aquilegia chrysantha is a Texas and southwest native, has yellow flowers and can take more sun than some varieties. McKana's Giant is the hybrid columbine most often sold. Large beautiful bi-colored flowers dazzle in woodland and shady area. Rocky Mountain columbine, Aquelegia caerulea; and wild columbine, A. canadensis, are other common columbines. Rocky Mountain columbine is the state flower of Colorado.

Common Name: Larkspur

The old fashioned larkspur is a drought tolerant reseeding annual, previously associated with delphiniums (now in the Ranunculaceae family). I’ve grown it in my alley, in the xeristrip, and its crept into my medium water-use zone. Deadheading keeps millions of tiny seeds from overcoming your garden next year, and also keeps the blooms coming. Larkspur can flower for six weeks. Again, deadheading is important to prevent a massive infestation throughout your landscape.

Common Name: Coral bells, Alum root

Heucheras are native to the North American continent and make wonderful foliage and flower plants for your woodland border. Grown mostly for its interesting, evergreen foliage, coral bells will continue to flower on mature plants if kept deadheaded into the summer. Although the native heucheras are great in themselves, there are hundreds of hybrid cultivars to choose from.

Common Name: Cascading Ornamental Oregano, Lebanese Oregano, Hop Oregano

Exciting perennial ornamental oregano for your low water-use or Mediterranean style garden. Spreads slowly by rhizomes and is easily propagated by root cuttings in fall or early spring. The flowers elongate as the summer progresses, eventually drying to a papery brown by summers end. In a wet fall, some new flowers may still appear. O. libanoticum is best placed to drape over a rock to showcase it’s drooping nature.

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