Evan Wakefield bought his West Seattle home in June for the vintage greenhouse that had been built there two decades ago. He already has big plans for it.
"I've been a big plant freak since I can remember and have dreamed of owning a plant shop," Wakefield says. "This greenhouse will be my main plant supply."
Whatever your goals, a greenhouse can stretch your growing season while adding a splash of magic to your backyard. For many home gardeners, the first step is figuring out how the space will fit their needs.
Tacoma-based garden designer Sue Goetz suggests thinking about purpose first -- whether you want a greenhouse for propagation, overwintering tender plants or as a plant-fueled retreat. This will guide key decisions about size, materials and design.
"It's a very personal choice," says Goetz, who has an 8-by-10-foot wood-polycarbonate greenhouse that shelters her collection of scented geraniums and lemon trees.
"I hang out there as much as I can," she says. "Right now, it's heaven because the lemons are blooming -- it's an aromatherapy moment."
Different gardeners bring different visions to their greenhouses, from cozy retreats to party-ready plant paradises.
For Erika Callies, her Camano Island greenhouse is a haven for plants and people. During the pandemic, Callies and her husband asked Mike Hablutzel of Seattle Greenhouse to build a custom greenhouse based on her drawing.
Complete with rattan chairs, a couch and a chandelier-topped dining table, the structure is a natural for gatherings, from summer through the winter holidays. Plants grow on every plane -- begonias, fuchsias and a spiral jasmine topiary. The greenhouse keeps them safe from frost and from deer, Callies says.
Find your fit
At its core, a greenhouse is a covered structure that lets in light but keeps out wind -- at varying levels. Greenhouses can be attached to a shed or home, ranging from a low cold- frame for fall and spring lettuce to a walk-in lean-to style. These are space-savers and keep plants close at hand.
Free-standing structures can enjoy greater sun exposure -- critical in our region depending on what you're growing. They range from budget-friendly, portable shelf units for seed-starting or covering a raised bed with hoops to a fully framed house. Permitting may be necessary for structures attached to the house or large greenhouses.
Your main decisions will center on the plants you're growing and their temperature needs. A small unheated structure may suit those just starting seeds from February through April. Hot-weather crops or long-term tropical residents require more equipment: lights, heat and watering systems. Lemon trees can live happily between 50 and 85 degrees, so Goetz runs a small barn heater to keep hers happy. But tropical houseplants require more heating.
"I think the biggest misconception is that people may look at a greenhouse as décor," says Oregon-based Mary-Kate Mackey, who has written a column on greenhouse living for UK-based retailer Hartley Botanic for 14 years. "The fantasy of a greenhouse is that it will be a warm space where I can curl up in a comfy chair and be surrounded by all my loving plants. People forget plants are dynamic."
Unlike a living room chair, which will basically look the same in three months, your tomato plant or orchid can change overnight. "I think the biggest thing about a greenhouse is that it's much more about nature than it is about the structure itself," Mackey says.
One of Mackey's favorite stories is about a greenhouse with a grape vine inside, dramatically providing shade in summer and sunlight in winter. "It was planted into the floor of the greenhouse, and then it grew up and over all of the greenhouse -- just, wow," Mackey says.
Growing needs
Think about how many shelves or benches you'll need, as well as how you'll water the plants and clean the space. Pests or disease can run through a greenhouse like wildfire, so make a regular maintenance plan. In fall, Goetz clears out the greenhouse, wipes it down, vacuums and prepares it for winter before bringing plants back inside from their summer vacation.
"Those nuances are important to think about in the beginning, because if you don't, many end up becoming storage units, which is sad," she says.
Wakefield keeps the needs of the plants -- including his 103 orchids -- front-and-center. "Twenty years ago, [the greenhouse] was state-of-the-art and it had operational vents. Those need to be replaced." His current greenhouse has a fan and a heater to maintain 70 degrees, keeping plants comfortable while preventing heat stress.
Temperature and humidity
As a closed system, greenhouses can get overly hot or humid in an instant, so it's crucial to set up systems that ventilate, shade and add air circulation as needed. Modern greenhouses may have automatic louvered vents attached to sensors and timers. Many growers add fans for mimicking wind, strengthening stems and boosting circulation to deter pests. You can buy timed venting arms for cold frames, but when it comes to hoop houses or mini seed-starting shelves, this usually means opening a door or unzipping a cover.
Hartley Botanic recommends siting free-standing greenhouses with the spine running east to west and one long side south-facing, away from tall trees. Level ground ensures drainage and stability and being near -- or adding -- a water source and electricity will make watering, cleaning and heating easier.
Nuts and bolts
Whatever size you choose, Goetz says, it pays to go for long-lived materials. Wood or rust-resistant aluminum are premium building materials, with wood needing more regular staining for weather protection. Less expensive alloys and plastics may bend or break more easily, and lighter structures can blow away in strong winds.
For the windows or roofing, glass is classic and lets in all the light, but it's the most expensive to buy and repair. Polycarbonate, which comes in varying levels of opacity and thickness, is less expensive, but becomes brittle over time. You'll choose based on the plants you are growing (some need as much light as possible) and the longevity you need.
When it comes to the base layer, experts agree a washable water-resistant or permeable surface -- like brick, concrete, stone or gravel -- is best. Goetz's is a combination of gravel with concrete squares, which drains well and is easy to keep clean. On hot days, she hoses the floor down and it releases humidity throughout the day.
A foundation wall of brick or stone adds an extra layer of warmth and keeps the frame off the wet ground. An old-school hack is filling large metal barrels, painted black, with water, The water gathers heat during the day and releases it at night.
While it's tempting to go big, choosing the right version for you is key. Experts suggest starting small to see how you use your greenhouse. Goetz says considering a lean-to or small polycarbonate model first is smart.
"If you think, 'Oh man, this was fun! I need more,' that tells you a more permanent structure may be worth the investment," she says.
Whether your goal is to harbor some cuttings overwinter or create a year-round sanctuary, you can extend your growing season, grow a greater variety of plants and enjoy your time in the garden more of the year.
"Be brave, start small and try it out," says Mackey. You future self -- and your garden -- will thank you.