The best time to plant your annuals, perennials, and shrubs
In order to know when it is best to start planting in spring you should know your average frost-free date (according to the Interactive Colorado Last Frost Date Map, our is June 11)! As climate change marches on, however, the historical date is in actuality closer to end of May.
The frost-free date is the date when it is fairly likely you will no longer get frost. Many plants like tender annuals and first-year perennials and shrubs aren't able to withstand frost, so knowing this date is important.
Some plants can go into the ground now, others must wait until end of May to be assured of survival.