Usually this column is dedicated to specific local gardening topics and reacting to local garden issues. Today’s article takes a broader, more global approach that I like to call a bird’s-eye view over local landscape facts.
We are a climate of extremes, but our local USDA garden zone is 6b with a definite influence from zone 7. This defines our area as mild, but with a definite winter and its potential for subzero temperatures. All local mountain communities fit this profile with little difference between Prescott, Prescott Valley, Chino, or Dewey. North or South facing slopes, how many boulders are present in a specific yard, and the presence of clay and/or caliche, are the influences that make up the subtle differences in our landscapes.
Local soils typically are clay with very little organic material. Therefore, soil preparation for planting is of extreme importance. It demands the addition of composted mulch to our soil either to hold in the moisture of granite soils, or to keep clay soils from compacting. Both our water and soil are very alkaline. Water pH is often 7.9 to 9.2 which rarely needs the addition of either lime or wood ashes, which would increase its already high pH.
The region is famous for our mild four-season climate with neither extremes of Midwestern cold nor desert heat. Intense sun combined with mountain arid air causes plants you may have grown in other areas to grow 20% shorter with leaves and flowers that are 20% smaller. Whatever a nationally printed plant tag suggests a mature plant’s height and width will be, always assume that in a local landscape the plant will end up on the shorter side. Most plant tag statistics apply to more humid areas of the country.
We don’t grow citrus, avocado, or palm trees because winter nights can dip to the cold side of freezing. However, low winter temperatures provide the chilling necessary to grow all the deciduous fruits and perennials that thrive in the coldest climates. The list includes apples, peaches, cherries, grapes, and berries. This climate also is conducive to blooming deciduous shrubs such as lilac, forsythia, crape myrtle, rose of Sharon, butterfly bush, and Russian sage. Some of the nicest roses in the country thrive here without the tedious demands of constant tending. Thanks to the low humidity and mild winters, mountain roses experience few problems with bugs, mildew, and virtually no black spot.
The first light frost happens on or about Halloween, depending on your garden’s specific elevation, but gardens look great through Thanksgiving. This makes the average frost-free growing season in the area approximately 150 days long.
The average last frost date in spring is around Mother’s Day. However, spring is so mild our cool season gardens can be planted as early as March. These can include lettuce, spinach, broccoli, potatoes, onions, radishes, and more.
Never, but never, underestimate the effects of Arizona sun, wind, and dry air. They are major influences in determining which plants do well in our landscapes, and which ones don’t. When selecting plants for mountain landscapes look for those with thick, leathery leaves; they allow plants to retain extra moisture and be less prone to tear in the area’s fierce windstorms. This is where it pays to talk to a gardening expert with some experience in local landscapes. It can save you a whole lot of time, energy, and expense in creating your landscape.
Interestingly, the mountain plant pallet is larger than selections in other parts of the country. We grow most of the East coast favorites, with a strong influence from the four season Southern plants. Very few plants sold in the Phoenix markets will winter over in the high country of Arizona so be selective in your plant purchases. Cold hardy agave, yucca, spoons, cacti, and brooms love the higher altitudes of Arizona. Again, select varieties that will grow in zone 6.
The most popular garden guide handed out at the garden center is one that I created 20 years ago. The “Prescott Garden Calendar” was created with our mountain gardens in mind. The monthly guide touches on year-round gardening and is helpful to gardeners new to the area and to old-timers who want to keep track of local season cycles. Ask for it the next time you visit. It’s free.
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This week’s featured plant is the Little Spires Russian Sage. This new Russian Sage is a shrubby summer perennial that screams “Southwest style”. With spikes of lavender blue flowers it adds a sense of lightness to gardens or containers. It is selected over traditional Russian Sages because it is shorter and stands upright so it doesn’t flop over in the landscape. The casual character says, “I’m from Arizona and ready to shine in the mountain sun.” Summer planting is best for this little one.
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This morning’s free gardening class is entitled, “The Joys of High Country Gardening”. Class begins at 9:30 and lasts about one hour. The August 4th class is the ever popular, “Keeping the Critters Out of the Garden”. Come early for this one; it was Standing Room Only last spring. Classes are held in Watters’ back greenhouse, so please consider this my personal invitation to join in the gardening fun.
Until next week, I’ll see you in the garden center.