by David Salman, Founder and Chief Horticulturalist at High Country Gardens
By choosing plants that are well matched to a region's precipitation, along with other factors (such as soil type, soil pH, and climate), a landscape will be colorful, waterwise and low maintenance. Thus, learning about a plant's preferences and then matching these preferences to local conditions will greatly improve its performance. This is what is meant when garden experts recommend using "regionally appropriate" plants.
Plus, we’ll share the best strategies for protecting your waterwise plants.
Looking at a rainfall map of the continental United States it is plain to see that rainfall varies dramatically across the country.
For example, the western edge of the Pacific Northwest is famous for its rainy weather; and the map indicates the rainfall here ranges between 50" to 60+" annually. But what this map doesn't tell you is that while this area of the country is soggy from late fall through spring, it's quite dry during the summer and early fall.
As another example, in the high desert of Santa Fe, NM we average 11 inches in a good year. Approximately 60% of it comes as thundershowers in a six-week period during July and August. Winter snows and occasional spring showers deliver the remainder.
Does the seasonality of a region's rainfall influence plant choices? Much of the time it doesn't, but there are a few exceptions.
For example, regions with Mediterranean climates have wet winters and dry summers, including California and the Pacific Northwest. Plants native to these regions are genetically programmed to go dormant or semi-dormant in the summer, when their habitats are driest. However, in irrigated garden settings, xeric non-native plants that originate in regions having summer rainfall can offer better summer garden performance. Chihuahuan desert natives like Salvia greggi 'Furman's Red', Penstemon psuedospectabilis (Desert Beardtongue) and Agastache cana (Texas Humingbird Mint) are excellent choices because they will grow and bloom when the west coast native flora wants to be dormant.
As a general rule of thumb, it is often easier to take plants native to wetter regions and grow them in drier regions. In the extreme, however, it is not a waterwise strategy to take species that need marshy conditions and move them to the desert.
Agastache Cana will grow and bloom when west coast native flora wants to be dormant.
Average quality soils that are near to neutral in pH (slightly acidic or slightly alkaline), aren't overly fertile and drain well are suitable for a wide range of plants. Given decent soil to grow in, plants during the spring and summer growing periods can tolerate more rainfall than they might normally receive in their native habitat.
However, this is often not the case in winter, when the plants are dormant. Too much water in freezing winter conditions can be detrimental. When growing a plant in cold weather situations that are much wetter than the plant is accustomed to, it is necessary to provide modified conditions to protect the plants from excessive winter/early spring moisture.
As in all things, moderation is the key. Plants don't mind being in conditions that are somewhat wetter or drier than their native habitats given other conditions like cold hardiness, soil conditions and sunlight requirements are also suitable.