Recent climate events underscore the evolving environment landscape architects must now navigate. In November 2023, The USDA released an updated Planting Hardiness Zone Map, shifting the City of Houston's classification from Zone 9a to 9b. The new boundary between these zones closely parallels the Grand Parkway’s alignment to the west and north. This reclassification indicates that Houston's average winter temperatures are now approximately 2.5 degrees warmer than those recorded for the previous hardiness zone map issued in 2012. However, recent severe weather events, such as Winter Storm Uri in 2021 and Winter Storm Elliott in 2022, have demonstrated that isolated major weather events can result in dramatic temperature changes, often reducing temperatures well below the average. These significant weather challenges, combined with the reflective heat and urban heat island effect found within cities, place additional strain on the landscape.

Navigating these complexities poses distinct challenges, causing area landscape architects to search for horticulturally suitable plants capable of enduring intense weather events. Trees and shrubs that once thrived under previous conditions are now struggling to adapt to the current climate. Thus, preserving the genetic diversity of native plants is essential for ensuring their adaptability to climate change.

Concerns have arisen that cultivars of native plants may not provide the same long-term ecological benefits as their naturally occurring counterparts, as evidenced by variations in performance among horticulturally developed woody ornamentals where cultivars of the same species have not performed uniformly. In developing cultivars, the nursery industry often selects specific traits to perpetuate, such as bloom color or plant habit. However, this selective breeding process can lead to the loss of genetically important characteristics, including cold tolerance and hardiness. This occurrence is illustrated by the varying survival rates among woody ornamental varieties in the latest freeze. A study conducted at Stephen F. Austin State University involved an assessment of freeze damage at the SFA Gardens. This research documented the impact on woody ornamental plants and highlighted species that either exhibited minimal damage or suffered significantly from the weather event. Species demonstrating high survivability rates were predominantly native to the region while non-natives lacked cold tolerance and experienced a wider range of failure amongst cultivars. Insights from this study, among others, are assisting Clark Condon in refining our plant selection process to create landscapes that are both durable and resilient.

Even beyond addressing extreme temperatures, urban challenges, and other environmental considerations, strategic planting design can significantly enhance the resiliency of the urban environment. This enhancement comes through habitat creation, carbon sequestration, and flood impact mitigation, largely accomplished by incorporating native species into project sites. These species have naturally adapted to the local environment, including its weather, soil, and rainfall, making them crucial for supporting local wildlife.