Mini-Greenhouse

A greenhouse changes how you garden. You start seeds a month earlier, protect tender plants from frost, keep your tomatoes dry during a rainy September, and harvest lettuce into December. It doesn’t need to be a glass cathedral with a stone foundation and automatic vents. A $200 polycarbonate kit or even a $60 pop-up shelf greenhouse gets you most of the benefit at a fraction of the cost. The hard part is choosing the right size and material for your yard and your climate. A lightweight pop-up structure that works fine in Southern California will blow away in a Montana spring. A heavy-duty aluminum-frame kit with twin-wall polycarbonate is overkill for a small balcony. We tested 7 backyard greenhouse kits — pop-up shelves, mini walk-in tunnels, and full-sized walk-in structures — to find the ones worth your space. ...

The vegetable garden has a cruel rhythm. By the time your tomatoes are ripening, the first frost is three weeks away. Your cold-weather crops bolt in the June heat. There’s a month in spring when the soil is workable but the nights are too cold for anything tender, and a month in fall when you’re still getting beans but the overnight dip kills your basil. A cold frame or mini greenhouse doesn’t fix the seasons. It bends them. A simple glass or polycarbonate box traps solar heat during the day and holds several degrees of warmth through the night — enough to start seedlings 4-6 weeks earlier in spring, harden off transplants without shuttling trays in and out, protect tender plants from late frosts, and stretch the harvest 4-6 weeks into fall. For the price of a decent pair of pruners, you can add two months to your growing season. ...