How to Build a Mini Greenhouse

Building a mini greenhouse in your garden is an inexpensive, easy, low-tech way to start gardening earlier in spring and to extend the gardening season well into fall. This greenhouse uses a hoop house design and it can be covered with plastic, row cover material or shade cloth, making it a versatile and useful addition to the garden. The greenhouse takes under an hour to construct and uses materials that you can find in any hardware store. Here's how to make it.

(6) 2-foot long 3/8-inch rebar stakes

18 feet of ?-inch flexible PVC or copper tubing

Mallet

Hack saw

Plastic sheeting, row cover or shade cloth

Scissors

Bricks

Two 6 foot long pieces of 1x1 wood (optional)

Staple gun (optional)

Install the rebar stakes that will support the hoops of the greenhouse. Place a stake in each corner of the bed and two adjacent from each other in the middle of the bed. Hammer each stake 18 inches into the ground with the mallet or a heavy hammer. (These directions are for a bed that is 6 feet long by 3 feet wide. If your bed is longer, simply add in additional hoops. You can build this greenhouse over both in-ground and raised beds.)

You can choose to use either PVC or flexible copper tubing. I chose to use copper because it is extremely durable and attractive. To make the hoops, cut the plastic or copper tubing into three 6-foot long sections with a hack saw.

To create each hoop, just slide one end of the tubing over a stake, arch the tubing over the bed and slip the other end of the tubing over the stake on the other side of the bed. Repeat with the remaining lengths of tubing. You should end up with three hoops over the bed. (A 6-foot length of tubing will make a 2 ?-foot-tall arch when placed over a 3-foot-wide bed. If you want taller or shorter hoops, or if your bed is a different dimension, simply adjust the length of the tubing accordingly.)

Once the hoops are in place you can choose what you want to cover the frame with. Clear plastic is a good choice in early spring and fall because it holds in solar energy and can heat up the air inside the greenhouse 10 to 20 degrees F higher than ambient temperatures (watch out though, it can get too hot for plants on a sunny summer day). A row cover cloth (like Reemay, Agribon or Tufbell) lets in light and air, and keeps temperatures inside the greenhouse 3 to 10 degrees F warmer. Or in midsummer, you can place shade cloth over the frame to prevent sunscald on peppers or to grow crops like lettuce that prefer cooler temperatures.

Drape the plastic sheeting, row cover or shade cloth over the hoops and cut it to fit. You'll want an extra 18 to 24 inches of fabric on all sides so you can easily secure it.

You can weigh down the edges with bricks or rocks, or you can staple a 1x1 to the long edges of the plastic, fabric or row cover. Then, using the 1x1 as a spool, roll up the excess material (towards the greenhouse). The weight of the material and the 1X1 will hold the cover in place. Weigh the excess material down at either end of the house with bricks. If you live in a windy area, you may want to clip the plastic to the hoops with large binder clips (or you can purchase special row cover clips from Peaceful Valley Farm Supply, see Resources below).

Plants tend to dry out more quickly when in the greenhouse, so be sure to check them often.

If you grow plants that need insect pollination to produce fruit (such as squash and cucumbers) in the greenhouse, you'll need to remove the cover when the plants begin to flower so pollinators can access them.