A lean-to greenhouse is a type of walk-in greenhouse that is attached to a larger structure, such as a house, garage, or shed. Lean-to greenhouses can be temporary or permanent and can be mini or full sized. The smaller versions fit easily on a patio or deck, and the larger versions may also be used as sun rooms.
Smaller, or mini, lean-to greenhouses can be put up by a homeowner. They generally take time to install, but often are a good choice over other mini greenhouse options if delicate plants will be grown. One of the biggest concerns when purchasing a mini greenhouse is that they often do not have enough insulation to maintain proper temperatures for delicate plants in colder climates. A lean-to greenhouse leaches heat from the supporting wall of the main structure, so it is more energy efficient and better capable of insulating plants than other mini options.
Depending whether the greenhouse is mini or full sized, lean-to greenhouse dimensions can range from 4-foot to 10-foot widths (1.2–3 m), and anywhere from 4-foot to over 20-foot (1.2–6 m) lengths. Enclosed in glass on three sides, the greenhouse's open side, along its length, is set against the support structure. A door is usually placed along one of the shorter sides. Roofs are sloping, either sharply angled or rounded.
Full-sized, also called hobby-sized, greenhouses should usually be put up by experts. These greenhouses are often expensive, since they are basically room additions to a home. A hobby-sized lean-to greenhouse, however, provides larger space, better stability, and direct access into the home.
Both mini- and full-sized versions are usually made with aluminum, though some are made from wood. Many manufacturers have options for steel bases, which provide more strength and stability than the aluminum versions. Most greenhouses will also contain vents, UV-coated panels, and a door. Vents may be manual or automatic, and doors are generally similar to storm doors, sometimes split so either the top or bottom can be opened independently.
Bookshelf greenhouses, a type of mini greenhouse, are sometimes also referred to as lean-to greenhouses. This is probably because, with their high tendency to tip over in the wind, they are often anchored to a house or other structure. Bookshelf greenhouses are compact and shelved, similar in design to a tall bookshelf. They usually have doors or sliding windows on the front to allow access to the plants.
Bookshelf options are ideal for small decks, patios, or balconies. These greenhouses can be hard to heat, but more expensive options usually come with extra insulation. Unlike other lean-to greenhouse options, bookshelves are not walk-in greenhouses.