That’s the rule of thumb, but the amount of sun that a given spot in our homestead gets each day will vary with the time of year. The sun is low in the early spring when we start our cool weather crops, like peas, so the days are short. Then the trees put out their leaves and some of what was in sun at nine a.m. is now shaded and it may be shaded again earlier in the evening.
The days get longer so what was only five hours of sun may increase to nine! But what about shadows cast by buildings? Those will shift with the angle of the sun too. So even though the longest day of the year is June 21, that doesn’t mean that every part of the garden will get the most sun on that date.
A tool that you can use are contour maps of your property showing where the sun/shade line is at various hours of the day. You might mark the lines at 9 a.m., noon, and 3 p.m. on the first of March. A spot that is in the sun zone on all three times has full sun.
On June 21, do it again, but make the intervals longer, say 8 a.m., noon, and 4 p.m. Those maps will be radically different. And perhaps, do it again at the end of September. Even though this is three months after the June 21st, it will probably be different in many cases than the March 1st map just because now the trees have leafed out.
Of course you don’t have to map the entire property every time. You may have too little sun overall but find that a spot on the driveway seems to have the most. Perhaps there are locations in that area where you might put a container or two for longer season crops, herbs for example.
Recognize, too, that this principle also applies to a flower garden. Most plants that are described as part shade do better as the hours of sunshine increase.
Article written by Glenn Palmer, Extension Master Gardener Volunteer.