Plant Sanctuary: Choosing the Best Greenhouse

Small greenhouses are manageable and are easy to set up. (GenOMart/Shutterstock)

Greenhouses rank high on every gardener’s ultimate wish list, and with good reason. They allow even the least experienced gardener to get a jump on a season, extend one, garden year-round, or grow successfully in an area where otherwise there would be too much pressure from pests, diseases, or predators.

Greenhouses fall into two general categories: compact and portable mini greenhouses (some small enough to fit on a balcony and broken down and stored when not in use) and large structures that can be either free-standing or attached to the home. Initial considerations include where it can be placed on a property (greenhouses need sun), whether it will need heating and cooling, and—here’s the biggie—how much time to dedicate to its upkeep.

Maintaining a greenhouse is a lot of work. With that in mind, it may be better to go with a smaller greenhouse, at least to start, with the thought that it’s more efficient to nurture fewer plants into an abundant harvest rather than spread oneself too thin.

Down-to-Earth Practicality

Budget is one of four key start-up considerations. Where do one’s dreams and one’s wallet meet? Think long term: It’s usually more cost-effective to buy right the first time rather than to upscale later. Some greenhouses, such as an attached conservatory, have the added benefit of improving a home’s value.

Water is the second concern. Limited availability or high cost may mean a smaller greenhouse is the way to go.

Next, what will the electricity requirements be? Start by considering general electricity needs, grow lights, and automated watering systems.

That brings up item No. 4 on the list: Will the greenhouse require cooling and heating? This depends largely on the plants grown, location, and whether one wants to grow year-round.

While all of the above may guide one toward a smaller set-up, the final decision needs to be balanced against the number of plants to be grown and their space requirements, which should allow for proper air circulation and growth. Jamming them in like sardines is not healthy.

Start (and Perhaps Stay) Simple

A compact and portable mini greenhouse is a great way to get started before diving into the cost and commitment of a larger structure. Or, it may be all that’s ultimately needed. Wonderful for small gardens, balconies, rooftops, or an indoor location with a south-facing window or grow lights, they provide an ideal microclimate for seed sprouting and seedling growth.

The smallest ones feature a footprint of around 20 inches by 30 inches and feature three or four shelves. They cost around $50 and are available in a clear, green, or white PVC (polyvinyl chloride) or PE (polyethylene) enclosure.

Which to choose? PVC is rigid and durable, provides excellent UV resistance and superior insulation, and has double-wall glazing. PE is less durable than PVC, particularly when it comes to UV radiation, but normally costs less, with double-layer PE providing robust insulation.

As for color, clear lets in maximum light without any color distortion and is ideal for tomatoes, cucumbers, and peppers. Green filters out some of the sunlight, so there is less heat buildup inside the greenhouse. It offers better insulation during colder times and is popular with orchid growers. White falls in the middle. It reflects sunlight to keep things cooler in high heat, but doesn’t provide the cool weather insulation properties of green.

Portable greenhouses are also available in “walk-in” models for multiple seedlings and larger plants that need protection from frost, pests, and animals. Common sizes include 6-by-4, 8-by-6, and even 12-by-8 feet and larger. Some come with shelving, while others are simple pop-up structures with roll-up side windows and a zipper door. All models can be disassembled and stored when not in use, which has the benefit of extending the PVC or PE’s lifespan.

Big and Bold

Popularized in the 18th century, classic glass and metal frame gable-style, Gothic arch, or A-frame (aka ridge and furrow) greenhouses can range from a DIY kit to a backyard masterpiece that requires permits and precise, often professional, design.

These designs take into account the location, type of plants grown, and water supply systems. Ventilation may require exhaust fans or louvers along the sides or above the doors. Heating for cold weather can be provided by space heaters, with options including forced-air, hot water and steam, or electric. Shade cloth or roll-up screens can be added for interior shade.

Other style options include slant-leg (for more floor space) or domes (for a modernist backyard). Fiberglass and double-walled acrylic or polycarbonate panels are durable, less expensive alternatives to glass. The ultimate in basic practicality is a Quonset hut covered with PVC or PE plastic. Needless to say, the last options won’t be as glamorous but can be much more wallet-friendly, and the plants won’t know the difference.

Inspired? Now is the perfect time to buy and build.

Garden Life

An attached conservatory, or plant sunroom, can be as small as a greenhouse window that places fresh herbs at hand in the kitchen.

Lean On Me

A half-greenhouse (or lean-to design), places the peak of the roof ridge against the home to save considerably on cost while placing critical utilities close at hand. Depths are usually limited, for a single-story house, to around 12 feet wide.

Status Symbol

The size of a full sunroom, which features a complete roof (not just to the ridge line as with a lean-to), is limited only by backyard space and zoning laws. Add a bubbling fountain to help maintain proper humidity, and roman shades or roller blinds to block out summer heat.

Multi-Use Space

Add some furniture that won’t mind the heat and humidity and cuddle up with a good book while the snow piles on overhead. Depending on the size, a plant-filled conservatory is a lush and magical environment for entertaining, too.