One has around thirty to forty five minutes to get in the light and shadow before a dramatic shift occurs - if that. Sometimes it seems shorter. I've been hauling this 30 inch by 40 inch sheet of illustration board into Redwood park to draw the above tree in the meadow. And then I have to go back on a sunny day at the same time of day to continue the drawing, and so on until it is finished. It doesn't mean every sitting can only be half an hour; one can remain and draw areas that are concomitant with the dramatic shifts.
This was started just when the leaf buds were unfurling, and they are now full leaves, which I don't know how much will affect the drawing, though I'm hoping it will be a good thing; I can erase parts and have leaves which will add further interest.
What I did not count on was the grass. When the drawing was started - about two weeks ago - the grass was below knee height. Yesterday I came into the park - without the drawing - and saw the grass was about as tall as me. The problem is, that is where I sit to do the drawing. I can't go to another position. Perhaps I'll bring along a machete.
That's the way things grow here in southern B.C. When they grow, they grow fast. So fast, I've been told even our hardwood trees aren't very hardwood. And I would have gone back sooner if it hadn't been raining so much.