For Gardeners in the US, this is a great website to figure out when to plant. It'sone of the best I have come across, for plant timing, I have found their timing to be one of the most accurate of all sites. You pick your State, city closest to you, or you can choose USDA planting zones, then pick the plant you want to plant and it has all the info for planting, and when not to plant.
When to Plant in Portland, OR