The Myth of Sunny Windowsills

After I wrote “Welcome Crocus!” a few days ago, I found myself thinking about the number of sunny days in February….6 out of 28.  That’s less than a fourth.  January had 12 sunny days out of 31.  A baby seedling on a windowsill would be stretching, stretching, stretching to search for sunshine on 41 days and only find light on 18.  And that’s assuming these are south-facing windows with no trees or buildings or overhangs or other obstructions that cause anything but full, brilliant sunlight on that windowsill during the day.  East and West windows only get sun half a day at most, and that’s just not enough for seedling health.  A seedling wants 8-12 hours of bright sunlight for good growth.    I’ve often heard people talk about growing on a sunny windowsill, and just took it for granted that it was a common practice.  Now, however, I wonder.  Are there really many windowsills that are truly sunny, or is it a false perception?  Does a cheerful, positive person with a sunny disposition mistakenly perceive that there is plenty of sunlight daily  coming through the window?  And conversely, does a gloomy disposition fail to note what sunshine is there?  Only accurate observation and recording will tell the true tale.   For instance, the above window in my living room faces east, but at 9 am it’s already losing what little sunshine there was.  And, it’s certainly not deep enough to hold many plants. Often by the time the morning haze has cleared, the sun has already moved too far to help plants in an east-facing window.    This west-facing window in my kitchen barely has room to hold a set of salt and pepper shakers and at 2 pm is still void of any sunlight.    Because of the Mansard roof, my home has lovely deep, broad windowsills upstairs so theoretically I’m blessed with good spots for seedling flats.  Not true.  There are no south-facing windows.  Most of the east ones are shaded by trees.  They are useful for wintering over tropical hibiscus like the one shown above, ferns, and other container plants and I’m happy for that, but for seed starting they are basically useless.  The window shown above faces east, and only the left side gets any sunshine.  In January and February the sun angles so that in all the west windows only the north few inches actually get sunshine for 2-3 hours before it sets, when the sunlight is actually already weakening.  Even the big bow window in the master bedroom only truly gets sunshine on the north end, but it’s enough to get amaryllis bulbs growing.    This likely explains why our grandparents waited to plant everything outdoors “once the weather has settled and the soil is warm.”  They had fewer windows, and without the modern R-factor of insulating windows available today, those would have been frost-covered, chilly places not beneficial to baby seedlings.  They really had few options for starting seeds early indoors, and few outdoors unless they created a hot bed with fresh manure.

We are lucky that there are efficient, inexpensive lights available for seed starting.  They can be used totally, or as supplemental lighting for windowsill babies on cloudy days or for those that don’t get a full day of sunshine because of location.  Even under-counter kitchen lights will help.  Just remember that it takes 2 hours of artificial light to equal 1 hour of real sunshine, and adjust accordingly.

So take a moment to really analyze those seedling flats sitting on a windowsill.  How many hours a month are they actually getting the light they need?  You may need to add some artificial light hours to compensate for “those sunny windowsills.”

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