Warm temperatures, blue skies and abundant sunshine. The good things. Primary reasons so many call Arizona home. However, lately you could say, “too much of a good thing” is well … too much. The recent spate of extreme heat, including record-breaking daytime temperatures and high nighttime lows, along with the lack of monsoon precipitation this summer, has been a challenge for people, equipment, animals and even desert plants.
Summers in Phoenix are already a stressful time for plants even in normal years. Typically desert plants are notorious for their toughness and ability to withstand a short spurt of high temperatures or extended periods with low moisture, even they have their limitations. Extreme heat over a continuous number of days and nights can affect plants by increasing water loss, vulnerability to sun exposure and root stress caused by rising soil temperatures. Together, all of these stressors can contribute to a decline in plant health, affecting growth and leading to higher susceptibility to disease and pests.
At Desert Botanical Garden, the goal is always to provide the plants with the best care possible under all conditions. This summer, the Horticulture Team with support from five members of Desert Horticulture and Conservation formed two Plant Care Teams. This allowed staff coverage on site seven days a week, ensuring there were always “eyes” on the plants and hoses at the ready. In these times of extreme heat, the primary steps taken are to monitor for signs of heat stress, provide supplemental water as needed, add shade clothes to protect from prolonged sun exposure and reduce the soil temperature with a mulch or top dressing.
In some instances, smaller plants exhibiting heat stress can be relocated back to one of the Shade Houses or Greenhouses in the Hazel Hare Center for Plant Science to mitigate the heat or sun stressor. In the fall, they are then replanted into the Garden in an area that may be more protected. For the plants in our Living Collection from other desert regions, the newest structure, Greenhouse West, has three bays—each separately climate controlled. Here we can maintain a more-regulated environment similar to where they originate, and it is all automated. The Priva computer system running the Greenhouse is able to be monitored and controlled by staff from their desk or home computer. Any anomalies in functionality that appear can be called in to on-site staff to quickly review seven days per week.
It doesn’t stop with the plants! In these times of extreme heat, the Plant Care Teams also keep an eye on each other and Garden visitors, using the same approach: monitor for signs of heat stress, offer a reminder to have and drink plenty of water, wear proper hat and sunscreen to protect from prolonged sun exposure and move to a shaded, cooler area. A 5 a.m. start time is not unusual this time of year.
Despite the extreme heat, some awe-inspiring plants will continue to thrive and unexpectantly offers rewards on the trails, at high noon, full sun, triple digits, in full bloom.
It seems for some … too much of a good thing is just right!