Gamble seems to have had a successful career, but was not one of the core group of California Impressionists. I justify that claim because after the 1906 San Francisco fire he was based mostly in Santa Barbara, slightly off the California Impressionist beaten track. Biographical information can be found here and here.
It seems that Gamble nearly always included wildflowers in his paintings, a feature that became something of a trademark. His paintings sold well, buyers coming from across the USA until the late 1930s when his eyesight began to fail.
Regarding his inclusion of flowers, the first link above states:
"When questioned by an interviewer about his passion for floral painting, he replied: 'I never painted them as flowers at all. I didn't even think of them as flowers while I was painting. They were just color patches to me, I simply liked the way they designed themselves across the field'. Many stolid Easterners considered his paintings pure fabrications, however when they made the trip to California's countryside in springtime the doubters were always proven wrong."
True, he didn't do close-up portraits of flowers. And it's also so that they add interest to the paintings in terms of composition and color schemes. But I also think he included those swathes of flowers because they helped make his paintings more marketable. Nothing wrong with that -- I'd rather an artist be prosperous than starving.
Also, as can be seen below, Gamble relied on several well-tested compositions for his California scenes.
This is the only dated (sort of) painting I downloaded.
I don't have this painting's actual title, if it ever had one.
Note the similarity of the hillsides in these scenes of different part of the state.
Again, two similar looking works.
Hillsides sloping down to the right, but with different kinds of flowers.
This has blockier brushwork. I'm not sure if it: (1) is a study, (2) is small, or (3) was painted when his eyesight started to go.
Same general location, similar brushwork.
This painting is quite different from the rest, and I'm not sure why. I have friends who live in Hope Range (nowadays a very upscale housing area) and have walked near where this painting was made. The view is toward the west. That low-lying coast takes in perhaps part of Goleta where the airport and University of California Santa Barbara are, and definitely shows the coastline farther west of there, but not the high inland hills.