One yard may have many climates Differences: Some areas are cooler than others

some are warmer or wetter or sunnier and therefore more hospitable to one kind of plant or another.

February 09, 1997|By Ary Bruno | Ary Bruno,SPECIAL TO THE SUN

Microclimates are an often misunderstood thing. Far from being the province of meteorologists and biological scientists, micro-climates are something all of us experience daily and can make use of. Perhaps you are taking advantage of one or more even now.

Microclimates are small areas within a larger geographic region that by some trick of circumstance or environmental factors has an effective climate different from the prevailing one (Baltimore's general climate, for example is listed as a temperate Zone 7, bordering on the tropics in July and August and Siberia in the winter).

They can be as tiny as a few millimeters, or as large as a few square miles, though these sizes are a little more extreme than your usual garden-variety microclimate.

Look around your yard and you may realize that you have several of these intriguing spaces. Some of them you are doubtless already using, but perhaps there are others that could be taken advantage of. Recognizing a microclimate when you see it is a great help for the gardener who is intent on growing a variety of plants or who wants to grow the ones he or she has more easily and efficiently.

Amazingly, even a small property may have a dozen or more of these individual areas. They can be defined by summer and winter sun, or shade, a neighbor's fence, a large conifer or even a tiny slope from one side of the garden to the other. Personally, I am happy to have the use of them, for it makes gardening much more interesting.

For instance, the hot, exposed southwest corner of my front porch abuts a paved, double driveway between my house and a neighbor's. To call this a "full sun" exposure is an understatement. This is broil city.

Perhaps you, too, are waiting for young trees to grow up and provide a little shade for such a corner. If so, this is a wonderful microclimate in the meantime for a quick-growing, drought-tolerant perennial or annual vine.

Chinese wisteria is such a plant, for although it likes its feet in the shade, it revels in the heat and laughs at the wind that whips around exposed corners. (Indeed, it is so happy in this microclimate it is threatening to take over my porch roof and the gutters, too, if I would let it.)

Or, you might consider this a prime spot for some warmth-hungry, tropical beauty such as mandevilla or any of the Ipomoea family (cypress vine, moonflower, firecracker vine).

Another type of microclimate may also be familiar to you if you live in a city. This is that lovely, narrow space, about 6 feet wide, usually on the north side between your garage and the neighbors' fence. You know the kind: bone dry or perpetually damp, full or half shade (defined as "it doesn't see the sun for several months during the winter").

While it is true it will never grow daisies, you may find it a perfect place for wild violets, day lilies, azaleas, monkshood, astilbes and many interesting and delicate woodland plants. If you can't beat a microclimate, exploit it.

Perhaps one of your microclimates resembles Arizona or the Mediterranean. This may be a west- or southwest-facing wall by a driveway or patio. These areas get the sun all day in summer and always seem to have poor, stony soil that is frequently alkaline as well, due to leaching from concrete foundations or paving.

As many temperate-zone plants give up quickly in these sites, you can instead take advantage of its Mediterranean characteristics. Such sites make fine homes for rosemary, thyme, sage, lavenders, dianthus, oregano and other herbs and flowers that flourish on those faraway wind-swept Greek and Italian hills.

Best of all, you too can help to create new microclimates, as well as use existing ones.

Planting trees is a great way to modify or create microclimates in the garden. Conifers, for example, create their own microclimate by shedding the moisture of dew and fog down their needles to their drip line where it does them the most good, though this often makes the ground beneath them generally too dry for much else. This makes them good companions for a driveway or patio, however, for which they will also offer a windbreak and shade.

Deciduous trees provide shade in the summer, but they can also influence such factors as soil acidity (e.g. oak leaves are low pH) and available topsoil zone, as well as having differing kinds of shade, from the dense shade of a maple or beech to the filtered-light shade of a Russian olive or mimosa. These would all affect the type of climate created and what other plants would do well there.

Slopes can be created artificially, to help provide better microclimates for half-hardy shrubs, tender perennials, and fruit trees. This is especially effective if the lower end leads out into an open area that continues to slope away so that cold, frosty air can drain away -- and provide the few degrees of temperature difference that determines whether you can raise camellias or not.

Climatic effects can be changed by using dark mulch around the plants in winter to absorb more solar heat and providing a screen or windbreak at the northern side, to reflect the winter sun and generate a few more degrees of warmth while protecting the site from heat-stealing winds.

So when one of those mild, midwinter days appears, you may want to go outside to see what other microclimates you can find or tinker with. Good sleuthing!

Pub Date: 2/09/97

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