Greenhouse Gardening

January 5th, 2011 by
For gardeners in many climates, winter is the landscape’s off-season. The trees have dropped their leaves, the perennials have gone dormant, the thick insulating layer of mulch has been put down in the beds, and the lawn mower has been taken to the shop for its annual tune-up. But that doesn’t have to mean that you’re resigned to just twiddling those green thumbs until spring. More and more gardeners have figured out how to dramatically extend the growing season with the use of a greenhouse.

Extend Growing Season with a Greenhouse

Most of us think of a big freestanding shed made out of glass, the prototypical greenhouse. Those transparent panels allow the sun’s rays (solar radiation) to penetrate. That heated air inside the greenhouse is trapped inside the structure, significantly warming up the soil, the plants, and everything else that’s inside. The temperature difference can be so drastic that it allows the greenhouse user to “cheat” Mother Nature, growing plant varieties inside that would otherwise be impossible just a few feet outside… even during the coldest months of the year. For most greenhouse owners, it’s simply a place to play in the dirt, no matter the weather. It’s a great place to start plants from seed, giving them a jump-start on the growing season. The delicate seeds are tended to in small pots on an easily-accessible workbench inside the greenhouse, then moved outside and planted in the ground when temperatures allow. Many greenhouse gardeners use their structures to keep their favorite veggies and herbs nearby and growing all year long. Plus, a greenhouse can make a fantastic focal point in the garden. Take a big-picture look at the overall effect that Heidi’s greenhouse makes in her Janesville, WI yard:

Use a Greenhouse for a Focal Point in Your Garden

Want a greenhouse of your own? You have several options. Of course, any professional landscape contractor or carpenter-for-hire would love to build one for you with all the bells and whistles. And for the gardener who wants it to be magazine-cover gorgeous and blend seamlessly into the landscape, it may well be worth the price tag. Kits are also available from many garden centers or online retailers. Think of it as a greenhouse-in-a-box. It’s dropped off in your driveway; you pick the location and supply the labor. Elaborate kits can run several thousand dollars, but there are also very simple starter models out there for just a couple hundred bucks! They’re a fairly easy and relatively inexpensive way to decide if greenhouse gardening is right for you. But for the more enterprising gardener who doesn’t mind going all DIY, there’s another option. It’s called a hoophouse. Instead of erecting a permanent structure, creating a hoophouse entails building a temporary greenhouse out of inexpensive (and often piecemealed) materials. YardShare veteran Lark has a great example in her Dousman, WI yard:

Inexpensive DIY Hoophouse

First, she created a large raised bed out of concrete landscaping blocks. Soil in a raised bed will generally be warmer than the earth on its own, but the concrete blocks will also absorb heat during the day from what sunlight there is, and then slowly release it into the surrounding soil overnight. Next, lengths of rebar were driven into the ground every few feet. Flexible conduit was slid over the rebar and bent over to the opposite side of the bed, creating the arched framework of a typical hoophouse. Plastic tubing and PVC are popular in this application, but you can connect shorter lengths of rigid pipe together with fittings to create any shape you prefer.

Hoophouse Construction

Clear plastic sheeting is then draped over the frame and serves the same purpose as greenhouse glass. The plastic sheeting is weight-anchored in place with spare board and cinderblocks. You can come up with a more permanent way of fastening the plastic to the frame (nylon zipties, etc.), but this low-tech method allows for easy tear-down when spring comes and you no longer need the hoophouse. The raised bed, the concrete blocks, and the clear plastic all combine to create a toasty environment inside the hoophouse that’s perfect for starting tender plants (or just keeping them going) over the winter months. But Lark has taken some extra heat-retaining measures, too. Remember that everything inside a greenhouse warms up with the sun. So she’s lined the perimeter of the bed with plastic jugs filled with water- that water absorbs a good bit of heat during the day, storing it there for the wee hours. And in the bed itself, Lark uses newspaper and grass clippings as a weed suppressant. But that homemade mulch also keeps warmth inside the soil, where it will do the plants the most good.

DIY Hoophouse Construction

So forget about this season being the winter of your discontent. Make it the year you let a greenhouse cure your winter blues.