Take a close look at the picture above.
Notice how there are areas of with low plants – in the foreground – and areas of taller plants – in the middle distance.
The taller plants are the light-loving plants, like nettles and brambles.
The lower plants, spread along the woodland floor, are the shade tolerators, like wood spurge and dog’s mercury.
You can see in the picture above, even though it is taken on a cloudy day, how dramatically the plants change when the woodland canopy opens up. Most people understand this rough relationship between light and life.
But now look at the picture at the bottom. Both pictures were taken near the middle of the day, but the one below was when the clouds had passed. Notice how closely aligned the areas of high light and higher plants is. It is almost a perfect fit, which is what we should expect.
However, whilst many walkers may be tuned to the fact that an opening of the woodland canopy means the plant life will change, only finely-tuned natural navigators will spot that the taller, light-loving plants don’t sit exactly under the canopy.
The sun pours in from the south and so the plants will thrive slightly to the north of the canopy opening, much more noticeably than they do to the south of it.
In the picture below, there are some very tall nettles thriving in a a patch on the right. It is in a sunbeam in this picture, but it is well away from the canopy opening. Well to the north of it.
If you take the time to notice the subtle differences between canopy opening area and plant life when the sun is out, you will be able to read the plants on the woodland more effectively when it is cloudy.
(The really beady-eyed amongst you will have spotted how many of the nettles are leaning towards the southern light too.)