L.E. Cooke Water Wise Landscape Trees & Plants List
As I write this the West is in a serious drought. Droughts or low rainfall years are not uncommon in the West. In the last few years we have seen several drought issues in Texas and even in Georgia and the Southeast. Cycles in rainfall and water availability happen. Surely, I have no desire to open the can of worms as to the causes or engage in that debate in this article. Historically we all have cycles of more or less rainfall / snow pack.
In our catalog, we have marked a column for "Drought Tolerant". There are many varieties that have a check mark in that column. So what does that mean for L.E. Cooke Customers?
Does Drought Tolerant mean it can live in the Mojave Desert like a cactus?
Is a Drought Tolerant tree in Arizona the same as a drought tolerant tree in Georgia?
Since we sell trees all over North America, the topic of Drought Tolerance is complicated.
The news will report a drought emergency in the East when it does not rain for 3-4 weeks in the summer because the farmers depend on nature to supply the rain for their crops. Whereas in the West a drought emergency is declared when 3-4 years of below normal rainfall occurs and the reservoirs become depleted. Clearly each region differs in needs and intensity.
This statement by the USDA helps (or confuses depending on how well you know your regional choice of trees).
The USDA statement on Drought Tolerance: What is the relative tolerance of the plant to drought conditions compared to other species with the same growth habit from the same geographical region? Drought tolerance is defined here in the following fashion: Imagine that in an acre of land there are low areas that have heavy soil and tend to accumulate more soil moisture, and higher areas that have coarse textured soil and tend to accumulate less soil moisture. Some plant species are most frequently found growing in the higher areas with the coarse soil texture. These plant species are considered to be more drought tolerant than the species that are frequently found in the low areas with fine textured soil.
This statement on the North Carolina State University Cooperative Extension website is also useful:
MEDIUM TO LARGE TREES
Disclaimer: Most plant prefer a moist, well drained soil. However, provided a plant is otherwise healthy, has had time to become established (normally one to two years after planting), and is provided appropriate cultural conditions (adequate soil drainage and aeration, mulch, moderate to low fertilization, proper pH, appropriate light level, etc.) those plants indicated as drought tolerant should be able to survive a moderate period of limited moisture (rainfall, irrigation). Drought tolerance does not mean the plants prefer hot, dry weather or that they will not be adversely affected by extended dry weather. Some decrease in growth or flowering can be expected during a period of limited moisture. Severe drought can result in increased insect and disease pressure, a decrease in leaf size and number, and a overall decline in growth rate and plant vigor. High temperatures and wind, heat and light reflection from near by hard surfaces, and high fertilization can increase the potentially damaging effects of low moisture on plant growth and survival. Fall planted trees and shrubs have demonstrated an increased ability to survive moderate moisture levels compared to those transplanted in the spring or summer. (Link to the above)
The following is a list of those items in our catalog that meet this guideline for drought tolerance in their normal habitat:
L.E. Cooke Water Wise Landscape Trees & Plants List
Additional References:
Texas Tree Planting Guide (Texas A&M)
Drought Tolerant Trees for Colorado Landscapes (Colorado State Forest Service)
Ron Ludekens 7-17-2014