Depends. Last year everything started turning green in March only to get hit with one last frost that stunted everything for the summer. Our "spring" is usually only 2-3 weeks long in April where everything goes from brown & dead, to green and needing to mow the lawn.
The mountains can expect to start planting gardens about Mother's day, and grow through Labor Day. Down here in the city, we start about a month before that and extend through mid October, although I have had to mow the lawn in early November before.