When Master Gardener writers met recently to schedule the next series of media articles, it was decided that January would be devoted to the topic of garden planning. As we discussed various topics, we were surprised to discover how different from each other our gardening experiences are.
As an example, when talking about “wildlife in the garden,” I mentioned that white-crowned sparrows and juncos had returned to my yard (at approximately 1,500 feet in elevation) for the winter. Another master gardener replied, “They’re in my yard (approximately 3,500 feet) all year round. A third, who lives in Oakdale, never sees these particular birds.
Moving on to discuss the topic of planting dates, we discovered that the Oakdale master gardener plants early in the spring. I, however, who spent 25 years living at an elevation of almost 4,000 feet, still can’t get used to planting before Mother’s Day — which means sometimes my veggies go into the ground late and end up battling excessive heat in Jamestown. The higher-elevation master gardener never plants before Mother’s Day. And, then, sometimes her garden faces late snow and killing frosts.
Certain plants, such as sugar and Jeffrey pines, thrive at higher elevations and would perish at lower elevations. Other plants, such as citrus, can grow easily in Oakdale, while they would freeze to death in Mi-Wuk Village.
In her award-winning book, “Gathering Moss,” Robin Wall Kimmerer says, “I’d climbed too many mountains not to notice the changes in vegetation with elevation. Elevational zonation usually results from temperature gradients and it gets cooler the higher you go.”
So, the first principle in planning your garden is: know your elevation. Elevation impacts so much more than just the average high and low temperature at your location. It can have an impact on soil types, rainfall, wind, humidity, heat and light.
Soils at higher elevations tend to be thinner, lower in nutrient content, rockier and more granitic. Lower-elevation soils tend to be much higher in clay content and, thus, richer in nutrients and water holding ability.
Rain shadow is the term applied to the effect of elevation upon precipitation. In California, storm clouds (usually) blow in from the west and are full of water content evaporated from the Pacific Ocean. As clouds rise up the western slope of mountain ranges — such as the Coast Range, the Inland Range and the Sierra Nevada — clouds cool and condense, releasing precipitation. As clouds cross over to eastern slopes, they contain less water; they become warmer and more diffuse. Lower and eastern slopes get less precipitation.
Elevation can also affect air movement and light. We’re all familiar with increased wind gusts over mountain passes. Alpine plants living above tree line are often low-growing or twisted in response to tougher conditions and prevailing winds at high elevations. And the tall evergreens of mixed conifer forests at higher elevations provide much more shade, lowering the ambient temperature and increasing humidity,
The USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov/PHZMWeb/ released in 2012 updated the more general information found on the 1990 map. As an example, when queried, the interactive 1990 map placed Jamestown, Twain Harte and Mi-Wuk Village all in the same zone. The 2012 map sorts locations into different zones, taking into account elevation, closeness to large bodies of water, and whether the location is in a valley or on a ridge top.
Be aware that hardiness zones or planting zones have large boundaries and may not be exact enough for your site. Zones grade into and out of each other gradually and irregularly. Rely on your own experience in your garden and determine the effects of your elevation upon your specific situation.
If you are looking for assistance in finding plants that will thrive in your garden, check out High Country Gardens online at www.highcountrygardens.com. Their interactive site will give you a selection of plants based upon ZIP code. Also, Las Pilitas Nursery, at www.laspilitas.com/comhabit/zipcode.htm, provides a list of California native plants based upon your ZIP code or city name.
Rebecca Miller-Cripps is a University of California Cooperative Extension Master Gardener of Tuolumne County who has lived in both high and low-elevation locations in the county.