March is not too early to start seeds inside a greenhouse in the Pacific Northwest. The key is to read the seed pack on when the best time to get seeds going. Cool season veggies and flowers such as alyssum, lettuce and spinach can go right into the ground. Warm season plants such as tomatoes, peppers and marigolds can be planted inside the greenhouse then transplanted outdoors when all danger of frost is passed sometime in May. Enjoy that new greenhouse and Keep Growing, Marianne Binetti