Most longtime Texas gardeners do not need to be convinced about the reality of climate change – we have seen it in our own backyards.
Here in Central Texas, many tropical plants which once had to be kept in pots and dragged into greenhouses to survive our winters, are now doing just fine outside year-round. Exotic vines and cold-tender citrus trees are now common sights in many area gardens. Responding to this new reality, the U.S. Department of Agriculture has revised its planting zone map to reflect the rising temperatures.
As if Texas wasn’t hot enough already, according to a study conducted by renowned Texas Tech climatologist, Katharine Hayhoe, Texas’ annual average temperatures are projected to increase by 5-10 degrees Fahrenheit by the end of this century.
Right now, rainfall in the Austin metro averages 31 inches per year, which is roughly equal to the water evaporation rate for this region. If Hayhoe’s heat rise projections are true, the evaporation rate for soil moisture will increase by at least an inch per month and Austin may start looking like the West Texas city of San Angelo even if our rainfall rate holds steady. And of course, with the expected increases in dramatic weather events, droughts will last longer and the rain, when it comes, will be increasingly torrential.
Yikes! What’s a gardener who is concerned about resiliency and sustainability to do? Well, for Central Texas gardeners, I suggest we look to the native plant communities to our west for inspiration. The plants found in the Hill Country and West Texas are well adapted to the hotter and dryer conditions we are expecting.
The Hill Country contains a variety of plant communities, but to simplify matters it is useful to divide them into two broad groups: the exposed plateau-top dryland savannahs with their thin limestone soils, and the more sheltered canyon lands (formed by erosion from streams) that typically have richer / deeper soils, at least seasonal moisture and shadier conditions. By simulating the drainage and soil conditions that exist in these locales and grouping the plants that prefer these different conditions together, we can create richly varied landscapes that use dramatically less water than non-native plantings. Gardening with these natives also helps us preserve our Texas identity and avoid the sterile gravel and artificial turf landscapes that are becoming common in the Desert Southwest.
The plants for a plateau-top or “upland” planting bed share the following characteristics:
- they are well adapted to sunny, hot locations;
- very drought tolerant once established (all plants should be watered deeply once per week during dry times in their first two years);
- grow in quick draining soils;
- survive in planting beds further from a water source;
- and they are susceptible to drowning and / or disease in heavy wet clay soils during monsoons.
Raised planting beds (6”) are recommended for “upland” plantings, especially if you have clay soils. This will help your plants survive the occasional torrential rains we are sure to experience. The following soil amendments and mulches / ground covers are recommended:
- 60% granite sand (for drainage and mineral content)
- 40% compost for nitrogen and other organic nutrients
- Coarse (crushed) granite or locally-sourced organic material for mulch with native turf grasses, perennials and annuals as groundcovers.
Trees and large shrubs adapted to the sunny, hot upland plantings include: monterrey oak, lacey oak, vasey oak, escarpment live oak, Ashe juniper, Texas mountain laurel, Texas persimmon, flame leaf sumac, palo verde, desert willow, Mexican redbud, kidneywood, anacacho orchid tree, and Texas flowery senna.
Woody lilies and cacti for an uplands bed include: paleleaf yucca, twistleaf yucca, havard agave, parry’s agave (Agave parryi, Agave parryi truncata and other cold hardy agaves), Hesperaloe parvifolia (red yucca and yellow yucca), nolina (bear grass), sotol, horse crippler cactus, claret cup cactus, and prickly pear.
Upland shrubs (s), perennials (p) and annuals (a) include: cenizo / Texas sage (s), agarita (s), esperanza or yellow bells (s), autumn sage / Salvia greggi (s), flame acanthus (p), four-nerve daisy (p), blackfoot daisy (p), pink skullcap (p), rock rose / pavonia (p), rain lily (p), bluebonnet (a), Indian blanket (a).
Turf grass (t), ornamental grass (o) and groundcovers (gc) for uplands: buffalo grass (t), Habiturf blend – buffalo, blue grama, and curly mesquite (t), Mexican feather grass (o), pine muhly (o), silver pony foot (gc).
The plants for a “canyon land” planting bed will share the following characteristics:
- adapted to sun, partial shade, or full shade;
- adapted to droughts, but will benefit from a deep once-per-week watering during dry times;
- need a higher percentage of organic content in the soil, but still quick-draining;
- and they perform better in areas closer to a water source for occasional irrigation.
Raised planting beds (4-6”) are also recommended for “canyon land” plantings in clay soils. However, the soil mix will contain more organic material that will provide nutrients and help maintain soil moisture. The following soil materials and mulches / ground covers are recommended:
- 60% compost base
- 40% granite sand
- Organic compost and mulch top layer (replenished annually) with native grasses, perennials and annuals as ground covers.
Trees and large shrubs adapted to the canyon land plantings include: monterrey oak (canyon or upland,) chinkapin oak, escarpment live oak & lacey oak (canyon or upland), cedar elm, big tooth maple, Texas ash, Texas mountain laurel (canyon or upland), Texas redbud, Texas persimmon (canyon or upland), yaupon holly & possumhaw holly, rusty blackhaw viburnum, Mexican plum, Texas crabapple, Mexican buckeye, flameleaf sumac (canyon or upland) & evergreen sumac
Canyonland shrubs (s), perennials (p) and annuals (a) include: fragrant sumac (s), turk’s cap (p), broadleaf salvias like Salvia coccinea (p), Big Bend and Hill Country columbines (p), native ferns (p).
Canyon ornamental grasses (g) and groundcovers (gc) include: inland sea oats (g), Lindheimer muhly (g), straggler daisy (gc).
Of course, there are many other plants that can be added to these lists, including a few well-adapted non-native species. However, I feel confident that these proven Texas performers can stand up to challenges of climate change while providing great pleasure to gardeners as well as shelter and sustenance for the many critters that have come to depend on our native plants. Green spaces and gardens cool down our yards and keep us refreshed – resist climate change and reduce watering by planting west!
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