My wife and I just returned from two wonderful weeks visiting, studying and hiking in the national parks of the Sierra Nevada mountains of California. We are talking about the big trees, high waterfalls, beautiful vistas and some record unexpected early season snow.

Of course I was very interested in the plant communities along the way. What struck me most was the importance of microclimate. The Yosemite Valley is just a mile and a half wide and yet the opposite sides of the valley support an entirely different group of plants.

With the high mountains, the side of mountain that catches most of the sun is much hotter and thus drier and vegetation is more sparse and challenged. The other factor is elevation. In those mountains a day trip is the same as traveling from the Florida border to north of the Hudson Bay if you are studying the plants.

While no where as pronounced here, microclimates are important in our local gardens. Soil, moisture, exposure, hills, wind and our proximity to the Chesapeake Bay, Atlantic Ocean and the Susquehanna River all come into play. Factors like these blur the lines between science and experience or art.

When I had the orchard I knew that a fruit blossom was most subject to freezing for a very short period just before they opened. If you can plant on a hillside, the air movement will drag the cold temperatures down the hill.

Another prudent move was to plant the same varieties of a given fruit on the north and south side of a hill. This usually staggered the bloom time and extended harvest season several days.

One of my favorite tales came from a man from Delaware. He was enthralled by the taste of our strawberries and wanted to grow the same ones in his garden a short hour away.

I told him the variety I planted and he ordered them. He wasn't happy. He repeated the process and again was not happy. He came to my fields and dug runners and again failed. Blame the microclimate.

On the ornamental side, I planted two identical coleus in identical patio pots and put one on the north side of my house and the other on the southeast side. You guessed it. You would have had a difficult time saying that it was the same plant.

Another example was the reseeding perennial blue flax. It danced through my garden and yet was a total failure on the other side of the hill several miles away.

This story has a moral. Many ornamental plants are easy to grow and will thrive regardless of what we do to them. Many others have rather exacting requirements. When you find a new plant try it, but don't make it the centerpiece of your landscape until you are sure you can grow it.