USDA Hardiness Zone 6

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

Other Cold Hardiness categories

Common Name: Chisos Rosewood

The Arizona rosewood is classified either as a quite tall shrub or short to mid height tree. One of it's best features is that it is evergreen, with slender glossy green leaves approximately 3 inches long. It puts on small white flowers in summer. One of the few drought tolerant, native, evergreen trees available in the trade. Slow growing.

Common Name: Rose mallow, Texas Star, scarlet rosemallow

Two southern native hibiscus suitable for the medium to high water-use garden. Large green leaves are superseeded by very large and showy flowers. H. moscheutos  is cold hardy and has some of the largest flowers, up to a foot across in red, rose and white, usually with a red eye. H. coccineus blooms scarlet 3 inch flowers -- not cold hardy but worth trying as a specimen container plant.

 

Common Name: Buffalograss

Buffalograss is North America's only native turfgrass, grows well in clay soils. A warm season grass that spreads by stolons, it is our best selection for low water-use lawns. It will survive very nicely on 15-20 inches of annual precipitation. For green turf summer long, a once a month watering is all that is needed. The common species is short to 4-8 inches, light gray/green to blue/green and goes dormant in fall, greening up again in May. Many newer varieties are being developed for wider blades and deeper green colors, such as Legacy® and Turffalo®.

Common Name: Creeping Oregon Grape Holly

Mahonia repans is one of my favorite plants with four seasons of interest. Low growing and spreading evergreen shrub is native throughout the Rocky Mountains. Bright yellow berries in spring are followed by black berries in summer and reddish winter foliage. The leaves are thick, glossy and holly shaped. Creeping Oregon grape holly prefers amended, humusy soil that replicates its native habitat as an understory plant in woodlands, but is low water-use once established. It will spread to cover an area, but not invasive. Very attractive!

Common Name: Grayleaf Cotoneaster

Grayleaf cotoneaster is a wonderful low growing shrub for the xeric garden. Evergreen or semi-evergreen in colder winters, it provides good winter interest, along with the other seasons. Small oval shaped silver/gray leaves cover the many arching branches. Tiny white flowers appear in late spring followed by red berries in late fall and winter. Low water use once established.

Common Name: Jupiter's Beard, Red Valerian

Centranthus ruber is a versatile plant, able to be used almost anywhere in the landscape except full shade. Long blooming except during the heat of the summer. Deadhead after the spring bloom for better appearances. Reseeds some, but not a problem. Quite drought tolerant, it will still do nicely in medium and high water use areas, except for wet, soggy clay. It appreciates good drainage and moderate amending but will do well in poor soil. Centranthus ruber 'Alba' is a pleasant white blooming variety. Readily available at local nurseries.

Common Name: Diana Rose of Sharon, Althea

Rose of Sharon, or Althea, is another reliable old-fashioned garden plant well suited for the Texas Panhandle. My favorite cultivar is Diana because of the brilliant, pure white 4-5” flowers and somewhat glossy green leaves. Diana is also one of the smaller varieties up to about 6 - 8 feet, while others can reach 10’ tall. Similar to most altheas, 'Diana' is a prolific bloomer.

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: Butterfly Blue Pincushion Flower

Scabiosa columbaria ‘Butterfly Blue’, though first discovered in Ireland, will thrive very nicely in your transition zone as a border plant along turf, where it’ll receive medium to medium high water. Amend the soil well with organic matter for rich blooms and keep it deadheaded to prolong blooms. Afternoon shade is recommended. A little more trouble than usual, but well worth the softening effect this compact, mounded and cheery plant brings to the border; a Perennial Plant of the Year for 2000.

Common Name: Rock Rose, Rose Mallow Pavonia

Although there is question in my mind whether pavonia is a native in Texas, it’s been naturalized for a long time and is found growing in the Edwards Plateau and south Texas. Pavonia has been cold hardy for me for at least 5 – 6 years. Readily reseeds to the point of being a nuisance, but this is a minor annoyance.

Common Name: Chamisa, Rabbitbrush

Chamisa or rabbitbrush is a medium tall shrub with blue-green stems that produce clusters of golden yellow flowers from September throughout fall, very showy in the landscape. Matted hairs on thin leaves cast a silvery appearance. Native throughout the southwest, in warmer climates it is evergreen. The official name has been changed to Ericamera nauseosa, but is still referred to as Chrysothamnus (meaning golden bush). Seeds prolifically -- is a good pass-along plant to friends, neighbors, relatives and passersby.

Common Name: Arizona Rosewood

Arizona rosewood is one of the few native evergreen trees or tall shrubs that are low water-use. Underused in the Texas Panhandle, mostly due to lack of availability. But with searching in Albuquerque or Santa Fe, one should be able to locate a specimen. Faster growing than the Chisos rosewood. Long slender, serrated, glossy green leaves with white flowers in summer.

Common Name: Cypress Vine

Cypress vine is a native annual tropical vine of the Americas, but has naturalized in Florida and the Gulf Coast areas; said to be cold hardy to Zone 6. Fine lacy or thread-like leaves twine as it grows, putting on scarlet red flowers in summer. In addition to being a climber, it can be used as a groundcover.

Common Name: Sand Lovegrass

Sand lovegrass is a warm season bunch grass typically found in sandy soils east of the Rockies over a wide range of the U.S. The grass clumps themselves are usually 12-18" tall with the plumes rising to 3-4 feet. Will grow in clay and poorer soils. Very pleasing wispy, arching habit with a soft sway and rustle in the wind. Can grow in partial shade. Seed heads are somewhat purple, fine textured. Will reseed. Low or no water-use.

Common Name: Oregon Grape Holly

Oregon grape holly is an evergreen holly-like shrub native to the Pacific Northwest Rockies down into California. Upright, it is slow growing but can reach a height of 8 feet. Best when grown in shade, especially out of afternoon sun. Prefers a more humusy soil but will only required once a month watering when established, however, can also be placed in medium and high water-use areas. Bright yellow flowers in spring, followed by dark blue berries in summer. The thick, glossy, holly-like leaves have spines at the points. Leaves turn from green to red in winter.

Common Name: Crocus

Spring blooming crocus is a favorite among gardeners, heralding the end of winter. Many species of crocus can actually bloom in winter months. I've seen crocus bloom as early as mid Janurary, although February and March are more common. There are many different species of crocus, most people choose them by color, height or bloom period. Their colors range from yellow to purple, lavender, violet and white, some in combination of colors. Commonly, Crocus chrysanthus, C. venus,  and C. angustifolius. C.

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: Standing cypress.

Reseeding biennial, native to Texas, and the southeastern US. The red tubular flowers make it attractive to hummingbirds. The upright stalks are brittle and break off easily.

Standing cypress will flower the first year, and may, or may not come back a second year, but you should see some seedlings. Transplant those. The glossy green foliage to the right in this picture belongs to Anisacanthus quadrifidus wrightii, flame acanthus.

 

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: Texas Pink Skullcap, Cherry Skullcap

A Plant Select Plant for 2004, Pink Texas Skullcap has often been listed as a Zone 7 plant, but it is reliably cold hardy in Zone 6 and in protected Zone 5b sights. I’ve grown it in my xeristrip since 2000. Long blooming with no maintenance ever performed. These low growing, mounding skullcaps are excellent for Panhandle xeristrips and rock gardens. Native varieties are S. drummondii, and S. resinosa. The hybrid cultivar, S. x ‘Violet Cloud’, introduced by High Country Gardens, is an excellent violet skullcap as well as the natives.

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.

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