Many plants are advertised or described as drought-tolerant, but what, if anything, does that tell us? Drought-tolerant where? Drought-tolerant when? Drought-tolerant if . . . what? By now, with unusually dry weather increasingly common worldwide, most gardeners likely are aware that drought itself may be defined in different ways, depending on one's perspective. Heteromeles arbutifolia (toyon) At the risk of oversimplifying, meteorological drought is lower than normal precipitation. Hydrological drought is lower than normal streamflow or groundwater levels. Agricultural drought is inadequate soil moisture for specific crops. Socioeconomic drought is insufficient water supply to meet demand. Ecological drought is insufficient
Global temperatures have been rising at least since the middle of the last century, and most projections anticipate that this trend will continue. Effects of warming vary from one region of the world to another but prominently include the likelihood that precipitation will shift from snow to rain in many snow-fed watersheds. It is also likely that snow will melt faster and run off earlier, changing the timing of peak streamflow. Snow is an important, even critical, seasonal water source for many regions with large mountain ranges, including most summer-dry climates. Snowpack accumulates in the mountains in winter when demand
Summer-dry climates are not dry climates. They are climates where rain falls mostly in winter. This is not a common arrangement. In most of the world, rain falls in summer or is fairly well distributed year round. Summer-dry climates are usually found on the west coasts of continents in the mid-latitudes where seasonally shifting atmospheric pressure cells block or open up to the jet stream and its storms. The photo above shows a coastal northern California climate in summer. The photo below shows a similar coastal northern California climate in winter or spring. Summer-dry climates vary considerably from one place
We want to change the aesthetic of what we expect to see in a garden photo in summer-dry climates. Beautiful photos of beautiful gardens inspire gardeners to mimic what they see. Many photos in garden books and magazines are from East Coast and English style gardens, that, while are certainly lovely in those settings, are wrong in more arid and summer-dry climates. Water is especially precious in summer-dry climates, lush images from other climates mislead gardeners to try inappropriate and unsustainable gardens. We want to inspire gardeners to choose plants that are water wise and garden styles that fit into the habitats and natural
We expect summers to be dry here in California. It’s a summer-dry or Mediterranean climate of wet winters and rainless summers. Gardeners learn to adapt and use plants that are native to summer-dry climates.