A young apple tree with fire blight. (Betty Cahill, Special to The Denver Post) We’re only six Mondays away from the spring solstice on March 20. The outdoor gardening season countdown has begun. This month’s focus is on getting the indoor seed-starting supplies ready to go. Plus, get going now on outdoor winter pruning on trees and shrubs, and keep your Valentine’s Day flowers fresh with these easy-care tips. Indoors Thinking ahead to the outdoor growing season, decide now (or very soon) whether to buy ornamental plants and vegetables from a garden center or if you will start your own from seed (you can do both).