USDA Hardiness Zone 6

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

Other Cold Hardiness categories

Common Name: Snow in Summer

A good drought tolerant ground cover for use in a border, in a xeristrip or a rock garden. Evergreen grayish green leaves with fine hairs (tomentose). Will grow too tall and gangling in too rich and moist a soil. Some areas of the country have noted Cerastium tomentosum to be invasive, but I have not seen those tendencies here. A good substitute for the annual alyssium. Cerastium tomentosum var. columnae is a commonly available variety.

Common Name: Red pincushion flower

Perennial with lyre shaped leaves, similar in appearance to scabiosa, native to central Europe. In fact, it's synonym is Scabiosa rumelica. Deep purple red pincushion-like flowers. Knautia macedonica may suffer from our alkaline soil if not well amended with compost and well drained. Will reseed some. Has a pleasant wild look. Popular with nectar feeding insects. Deadheading doesn’t seem to be necessary.

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: Violet Cloud Hybrid Skullcap

A new hybrid skullcap from High Country Gardens. A cross between two native skullcaps, Violet Cloud likes the soil lean and well drained. A sparkling addition for the rock garden, xeristrip and any low water-use area. Additional watering is required during establishment the first year, after that, it should be drought tolerant.

Common Name: Prairie Sun Black-eyed Susan

Rudbeckia is advertised as heat and drought tolerant, but I have not found it so. I’ve found it to require at least weekly watering during the heat of the summer. A shortlived, southern native perennial, it likes the humidity and rain from southern climes. These very large and stunning composites may be worth your effort, just place within the correct hydrozone.

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, yellow

Yellow honeysuckle is a much better choice, along with Loncera sempervivens, than the traditional and invasive Japanese honeysuckle usually sold. Fragrant and yellow blooming, a good climber and groundcover. Average garden soils with low and medium water-use. Can be low water-use once established.

Common Name: Switchgrass

Switchgrass is one of the best native ornamental grasses of our tall prairies. Switchgrass forms upright bunches of wide 1/2 inch green blades, with open pale purple inflorescence arising another 2 feet in late summer to fall. Switchgrass will thrive with every other week supplemental irrigation. There are many varieties of switchgrass, 'Prairie Sky' is the most drought tolerant (low, xeric) with blue blades. Other fine selections are 'Heavy Metal' with metallic lavender blue foliage turning reddish towards fall, and 'Shenandoah' with leaf blades tipped in red.

Common Name: Gray Santolina, Lavender Cotton

Lavender cotton, or gray santolina is a low mounding woody subshrub that should live on the lean side. Not that it won't overgrow if fed. It will maintain its compact shape in poorer soils without amending or fertilizing. Small silver gray leaves cover the shrub. Tiny yellow button flowers appear in summer. Evergreen, the santolinas are native to the Mediterranean area. Aromatic and edible, it's leaves were used as a flavoring in broths, sauces and grain dishes. Low water-use.

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: Bearded Iris, Hybrid Cultivars

Distinctive flat, thin upright leaves with flowers arising from the stem.

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.

Common Name: Prairie Skullcap

Our native skullcap is one that should be included in every drought tolerant landscape, short lived though it is. This is the kind of garden-worthy plant we all desire, neat, compact and all season blooming with no maintenance to speak of. You just can't go wrong as long as your soil has decent drainage. It reseeds some, but to me, this is just a bonus.

Common Name: Goldenrod 'Wichita Mountains'

This variety purchased from Sunshine Nursery in  Clinton, Oklahoma is drought tolerant, I've planted it in a low water-use bed. The flowers are so dense and golden, it looks like a golden torch. Sometimes seen as Solidago speciosa rigidiuscula, 'Wichita Mountains'

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: 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: 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: Crape Myrtle

Grown in the South for decades, most people think of crape myrtle as a native American plant; it is however native to China and Japan. Small tree or large shrub that is cold hardy to Zone 7.  I’ve grown the same crape myrtles for over 20 years, but they’re planted close (too close!) to my bricked house on both the northeast and northwest corners. They’ve been stem hardy, not just root hardy, and have grown up to about 10-12’. In most cases, crape myrtle will not grow into tree form in the Panhandle, but there are mature, tree size crape myrtles in Amarillo.

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