High Plains Gardening
The gardening website of the Texas High Plains Region
AHS Heat Zone 8
Plants that will live in areas that experience 90-120 heat days (AHS Heat Zone 8) each year where temperatures exceed 86 degrees F. Except for a few limited areas in the Texas Panhandle, our AHS Heat Zone is 8. Plants rated lower than AHS Heat Zone 8 may not survive the summer's heat.
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.
It is so refreshing to see the rain lilies bloom after a long hot summer. Whenever they begin to bloom, I know the worst heat is over. Rain lilies are a delightful flower that sends up glossy green, grass-like leaves from its bulb in late spring. In mid to late summer, pure white flowers resembling a crocus open and continue through September, usually after a good summer rainfall. There are quite a few species and varieties (of various colors) of Zephrantes, however, Z. candida is the only rain lily cold hardy in Amarillo. I've grown it successfully since 2008.
Cliff fendlerbush is another Texas and Southwest native shrub too little used in the xeric landscape. Springtime lifts the cliff fendlerbush above the ordinary into prominence in the landscape. It is said the ravines and arroyos look dotted with snow from a distance, so profuse are the fragrant, creamy white, sometimes with a pink tinge, four petaled flowers in May and June. It's natural element is rocky arroyos (rupicola=rock dweller), cliff ledges and limestone soils with good drainage that average 12-18 inches of moisture with hot sunny days.
The vitex, or chaste tree is a small tree or a very large shrub, depending on water and climate, and is cold hardy to the Texas Panhandle. Low water-use once established, it can grow well in higher water zones. It is called the summer lilac because of the similarities of its flowers to the lilac shrub. Vitex varieties can be found in blue, lavender, and pink fragrant flowers. The leaves are similar to those of the marijuana plant. Vitex will sucker, especially when given ample water. It is native to southern Europe and Western Asia.
Small green gray evergreen leaves forms mounded, low growing xeric plant with small white flowers in late spring. Does not spread vigorously. Easily propagated by root cuttings. An alpine from the Balkans region.
Delicate fern like foliage for your shaded woodland areas. Will grow in a low water-use zone, however, the foliage will disappear in summer. Delicate tubular, yellow. White and blue varieties have been available locally. An excellent choice for underplanting trees, especially for a medium water-use zone. Will reseed.
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.
A long-lived evergreen penstemon for the average bed or border. Small orange red tubular flowers attract hummingbirds, as do most red tubular flowers. Low growing and longer flowering than most, especially the more mature the specimen.
After several years, the pine needle like foliage can resemble a miniature bonsai. Pineleaf penstemon is also a must-have for the low water-use bed or border or rock garden because of its evergreen foliage and longer blooming nature. In late summer, snip off the dried, spent flower heads; some re-blooming may occur.
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.
Not our old fashioned garden zinnia. Zinnia grandiflora is the native zinnia for most of the Midwest, West and Southwestern parts of the United States. So widespread a wildflower, each region has named it theirs: plains zinnia, prairie zinnia, desert zinnia and Rocky Mountain zinnia. A terrific low growing and spreading groundcover for poor soils needing no supplement irrigation. Rugged! A survivor without being a pest!
Desert marigolds are one of the prettiest desert flowers. The plant forms a neat compact rosette of finely cut silvery green leaves from which stems emerge topped with a bright golden daisy like flower. It is considered either an annual or short lived perennial. Scatter seeds from the spent plant to insure its return the next season. Over watering will doom this beautiful plant. Desert marigold can be seen blooming in the desert in winter and spring. In my garden, it's blooms begin in May and will continue sporadically into fall. Not awfully reliable in cold hardiness here.
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.
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.
White flowering zinnia is native to the Southwest and Northern Mexico. A low mounding plant, it becomes completely covered with small white flowers with a central yellow disk, similar to our native prairie zinnia, Zinnia grandiflora. Blooms from June through fall. Desert zinnia is toxic if ingested by humans.
New Mexican privet can be viewed either as a tall shrub or smaller tree. New Mexican privet will flower (tiny yellow) before leafing out with small oval glossy green leaves to be followed with black berries in the fall. Heat and drought tolerant will live in most soils and water-use areas. Attractive taller plant for the home landscape, similar to the yaupon holly in form.
Bush morning glory is a non-vining herbaceous perennial with a deep taproot, allowing it to be drought tolerant, but difficult to transplant. Arching branches with narrow upright green leaves emerge from the taproot. Summer blooming with 3 inch pink to purple funnel shaped flowers that open in the morning and close in the afternoon. Bush morning glory typically inhabits sandy and sandy loan plains, meadows, prairies and roadsides.
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