Microclimates!

"Mad dogs and Englishmen

Go out in the midday sun." (Noel Coward)

Any owner of un-mad dogs has watched their pet move from morning sun to midday shade, and then follow that shade around the house on a hot summer day (I don't know about Englishmen...). They are seeking the cool effects of the microclimates created by the house or trees.

Weather is what happens day to day--rain, wind, heat, cold-- and climate is the sum of all that weather year around. Microclimate is a small portion of your yard which increases or decreases the intensity of the climate: direct sun or shade on a wall, protection from wind, reduction of frost due to an overhang. These differences can be substantial, literally meaning life or death for some plants!

The basic things plants need--air, light, water, nutrients, and protection from weather and pests--are all affected by the microclimate. Your house has the greatest impact from the overhangs and the shade patterns it casts, but the trees you plant and landscape structures you build make a big difference as well.

It is this mitigation or increase in the intensity of climate which makes these useful or challenging parts of the landscape. They give us the opportunity to grow plants that are a bit out of their range, or they force us to choose plants that can take more extreme conditions.

Take a quick walk around your house and you'll feel as much as a 20 - 30 degree temperature difference. The north side is much colder in the winter, while the south side is flooded with winter sun and warmth. The west side may be so hot on a summer day that you can't bear to stand there for long. If you're uncomfortable, your plants will be too! The east side is a pleasantly sunny place to sit in the morning, and cool and shady in the early evening. A gardener shopping for a home would be well-advised to avoid those with mostly west and north exposures, as there are fewer plants for those more extreme exposures.

Around your house:

East is the easiest and most benign exposure. Full morning sun and afternoon shade make it easy to grow plants described as preferring full sun or those that prefer partial shade. Morning sun is cooler and less intense than afternoon sun. This takes some getting used to if you moved here from the coast, where mornings are foggy and afternoon sun is accompanied by the ocean breeze. Our reliable delta breeze doesn't arrive until early evening--after the hottest temperatures of the day.

In the winter, east is second best exposures for tender plants, after South-facing walls, because the morning sun warms the east side earliest, reducing the likelihood of frost damage. Avoid planting trees on the east side.

Shade-lovers are fine in morning sun, and it may be enough for sun-lovers such as roses. Strong winds here rarely come from the east this is a great location for Japanese maples. Most woodland-type plants prefer east exposure: Camellias, azaleas, ferns, Bleeding heart, etc.

West side--hot, hot, hot!

South side--

There are a few plants which require winter chilling to break dormancy and bloom properly, so avoid winter-protected locations for these. Lilacs and peonies planted up against an east or south wall may never bloom! Plant these out in the open where they will get cold in the winter. Or mulch them with ice cubes a few times during the winter (it really works).

North side--

A north exposure open to the west is the most extreme. Consider planting a tree or large shrub to help moderate the heat and wind. A shade tree planted to the west or northwest of your house can make a big difference by reducing summer temperatures and wind. Sheltered from the extremes, this cool exposure can then be ideal for ferns and similar plants. It may even be so damp that moss grows.

Your lawn is often a challenge against the north wall, as the long portion of the year without direct sun precludes most grass species. But ground covers can provide a nice green cover: Baby's tears often invades where the lawn "should" be, stopping abruptly at the line of summer sun.

Out in the yard

The canopy of a large shade tree reduces temperature dramatically, increases humidity, and buffers wind. The plants that will succeed vary, depending on how deep the shade is that the tree creates. Sycamore, birch, and honey locust are examples of trees which provide high, filtered shade. Mulberry makes very deep shade, with only limited plants to choose from. Encouraging tree plantings by joining groups such as TREEDavis can help moderate the weather in your entire neighborhood.

A windbreak of evergreen trees and large shrubs, mixed with small deciduous trees, can surround a sunny garden area to "build" a garden room with a backbone of plants that provides shelter. Remember that the gustiest, driest winds come from the north, and the hottest sun slants in from the west. An arbor with a vine on it can quickly mitigate these extremes.

An enclosed courtyard is warm and sunny, but protected from afternoon sun and wind inviting sun-loving flowers and subtropicals. Note that the north-facing wall will need shade-lovers. A small tree, or a shrub trained up like one, can buffer the hotter west-facing wall. Keep your plants in scale with the small dimensions--the visual focus is downward, not expansive. Vines can be useful to provide foliage without crowding limited space.

In California we use our landscapes as outdoor living spaces to a degree that isn't possible in freezing, muggy, buggy climates. Careful design can enhance these different microclimates, creating privacy nooks, sunny sitting areas for the spring and fall, shady retreats for the summer, and protected niches for the winter.

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