Jamieson, Fausset and Brown on Genesis 1:11

11. let the earth bring forth--The bare soil was clothed with verdure, and it is noticeable that the trees, plants, and grasses--the three great divisions of the vegetable kingdom here mentioned--were not called into existence in the same way as the light and the air; they were made to grow, and they grew as they do still out of the ground--not, however, by the slow process of vegetation, but through the divine power, without rain, dew, or any process of labor--sprouting up and flourishing in a single day.