Thaumas P. Ehr, Landscape Architect

In Arizona,Microclimates Make all the Difference.

Growing up in the Midwest, where my family had a nursery, I was always fasinated by how and where things grew.

In the nursery,some things grew better in certain places than others,but in nature everything grew always in the right place! How come?


I eventually figured out the secret: Microclimates-warmer or colder areas within a garden - allowed for certain plants to thrive.Microclimates can differ greatly from the inner-city core,to the sprawling suburban landscape and to the open desert. They can be beneficial, or they can pose serious challenges.

But when you do your research and make it a point to study microclimates, they can help you solve your garden design problems. Here are some tips to take advantage of and to learn from microclimates on your property:


1. Study your property. The Valley has two distinct climate zones, according to the U.S. Department of Agriculture's new 2012 plant hardiness zone map. Most of the Valley lies in zone 9b, where the average annual extreme minimums are 25 to 30 degrees.


The city's central core and the surrounding higher-elevation mountain areas in Paradise Valley don't get as cold, and they are listed as 10a. These areas see less frost; the average annual extreme minimum is 30 to 35 degrees.


This new USDA map accurately portrays what has occurred over the past 30 years. The hard freeze of February 2011 caused serious damage to outdoor plants not placed in a protected location. You can typically protect plants from frost and summer extremes by paying close attention to micro- climates.

Temperatures can be modified greatly with the proper placement of a shade tree, or by nestling a plant up against a wall or under the canopy of another tree, for example.


2. Note shade patterns. A north wall is usually shaded and is a good place for leafy plants, perennials and succulents that prefer summer shade.


Leafy plants include jasmine, columbine, pittosporum, Mexican honeysuckle, and salvias. North walls are definitely the coolest spots during the summer months.


East walls are great for most succulents, including aloe, euphorbia, and portulacaria that like the morning sun, but not the afternoon sun's intensity.


South and west walls are especially intense. These areas are great for plants that require more warmth in the winter, such as bougainvillea and many columnar cactuses and dwarf palms. Consider using exotics such as boojum trees, Bursera, or Totem Pole cactus.


You must, however, create some overhead shade from the afternoon sun to be successful during the brutal summer months. Plant a tree nearby. This will allow you to take advantage of the spot.


3. Use caution with lower ground. Sloping ground and lower spots in the garden can be significantly colder, and you should be aware of these areas.


Only use plants that can take the extra frost in low-lying areas. This is a good spot for native plants, including prickly pear, hedgehog cactus, yuccas, nolinas, and agaves.


The Southwest has an abundance of plants that thrive in this area and nowhere else. I believe our gardens should somehow connect to the distinctive regional look of the surrounding natural landscape.

Gardening in the lower or sub-tropical deserts is a challenge. With only 8 inches of rainfall a year (on average), most areas have summer temperatures averaging 105 degrees. Most locals do their gardening in the fall when the weather cools. This makes sense: less stress to plants and people.


Try to match your plants to their location, experiment a little. Don't be afraid to fail. Even I don't always get it right!


Don't be afraid to questions of your local nursery professionals. Observe why one plant does so well in a garden and its location. Do some research, and you can continue to make better choices.