Magic has its time and place. All magic can be done anywhere, but some things work better in the day, or in the night, in an open space under the stretching sky, or in a secret place all cosy and warm.
Even with magic it can be hard to use Naturecraft indoors. You gotta be under the sun and clouds, in the wild world untouched by man or elf or dwarf, to really see how powerful the magic can be. For growth or sowing, spring dawns are best. Out here in the lowlands we can walk for miles in this low sun without seeing or hearing another living thing, and that is part of the spell, I think.
And yes, magic is not set in stone; it is how we direct the power that sees the work done, not the words muttered or the shapes drawn or herbs used. Those things are guides for mages, but we can also find our own methods to suit our own ways.