Trees are a treasure, a joy to have around.  They provide a habitat for birds, insects and other critters; act as a buffer against wind, rain and snow; and are the main generator of atmospheric oxygen and consumer of carbon dioxide.  Plus, they are beautiful to behold.  If they are not the focus of a picturesque view, they are probably framing it.

But sometimes they get in the way.  Usually, this is merely an annoyance, such as when they block the view (see, for example, August 12, 2013).  Other times, though, trees can block solar exposure, often to detrimental effect.  I’ve become painfully aware of this phenomenon in the garden as the summer has wound down.

I noticed this morning, for instance, that the garden is still in the shade long after 8:00 am, the hour at which it came into full sun at summer’s peak.  Two months after the summer solstice, however, the sun is already quite a bit lower in the sky and as a result, the tall trees to the east of us are obstructing its direct rays.  It is light in the early morning but it is not exactly sunny.

Similarly, this afternoon, the tips of the fir trees on our neighbor’s property, just to the southern side of our pool fence, are casting a shadow on the south wall of the planters.  The inclination of the sun will only get lower as the days pass while the trees will only get taller with each passing year.  Soon, the shadows will pass across the vegetables shortly after midday, further shortening the growing day.

This is in spite of the fact that we removed two large trees in the spring (see May 17, 2013 and May 17, 2013, part 3).  Their absence has made a huge difference in the garden’s afternoon sun exposure but as it turns out, the impact’s duration is limited to the period starting a month before the solstice until a month afterwards.  Outside of that two-month range, we will feel the effects of the changes in solar exposure in the house more than in the garden.

Which brings us around to the beneficial aspects of solar shielding (to end on a positive note, lest anyone think that I am hostile to trees).  In warm climates, properly placed trees prevent solar gain within buildings and reduce their cooling load.  Where the weather is warm the year round, evergreen trees maintain a constant screen.  Alternately, where winters are cold, deciduous trees conveniently drop their leaves, allowing solar radiation to pass and provide natural heating.

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