March
From Gardenology.org - Plant Encyclopedia and Gardening wiki
This information is laid out for gardeners in the northern parts of the Northern Hemisphere. Those in the southern South Hemisphere should add 6 months to this one in order to adjust for the difference in seasons. Those in tropical climates only have wet and dry seasons, so much of this does not apply to them.
http://www.bbc.co.uk/gardening/today_in_your_garden/jobs_march.shtml