A backyard greenhouse can extend the growing season very effectively. Start your tomatoes early in the spring for planting out into the garden. Plant lettuce, kale, or spinach almost year-round. Just be careful to get the proper varieties from your seed company because some lettuce varieties do well in cool climate conditions and others do better in the summer heat.   Dwarf varieties of citrus and other fruit trees are also fun to raise in a greenhouse! You will find the most significant advantage in extending the growing season in early spring and late into the fall. It often depends on what you want to grow and how much you want to spend. Some varieties of greens can be grown all through winter in a small greenhouse with minimal heating, while other plants require a lot more care. We recommend that you research any plants you are considering planting first.