When starting plants in the Garden Starter System, keep in mind that different plants can hit the garden at different times.
Cool weather crops like lettuce, beets, spinach and broccolli can go out just as soon as you can work the soil -- early March in Colorado.
Warm weather crops like tomatoes, peppers and squash, can't be transplanted out until AFTER the last chance of frost (that's in mid-May here in Colorado).
One way to balance this is to space out your warm weather crops at intervals through the Garden Starter Tray. Then, as you transplant out the cold weather crops, your tomatoes and peppers will have more room to grow as they stay in the garden to keep warm and grow until they are ready.