How to Make a Hoop Greenhouse

By Diana Lynn
Photographs by Susy Morris
Illustrations by Robert L. Prince

It’s getting cold, so hoop it up! With a hoop greenhouse, you can grow food all winter and get a jump on spring planting.

WHAT YOU NEED TO MAKE A HOOP GREENHOUSE

Shovel
Rake
Pruning shears
Measuring tape
Scissors
Pencil
Hammer
Wood saw
Electric drill
Outdoor twine
Three 8-foot two-by-fours
Four 1-by-2-by-12-inch landscape stakes
10 1 1⁄2-inch galvanized tube straps
Eight 3-inch exterior wood screws
Eight 4-inch exterior wood screws
20 1-inch wood screws
10-by-25-foot piece of 3-6 mil plastic sheeting (plastic sheeting comes in thicknesses rated by mil — that’s one-thousandth of an inch, or the width of a human hair.)
14 plastic clamps opening at least 1 inch (or make homemade garden hose clamps. Instructions below)
8 feet of 1-by-2-inch furring strip or lath (other straight and thin outdoor materials can work too.)
50-foot roll of 3/4-inch poly pipe (1/2-inch PVC pipe also works)

HOW TO BUILD A HOOP GREENHOUSE

1. Pick a flat and sunny location for your hoop greenhouse. Measure a 4-by-8-foot rectangular area. Prepare the ground for planting by digging up the soil and raking it.

2. Place a two-by-four vertically on each of the two long sides of the garden bed. Saw the remaining two-by-four in half, and lay down those two pieces on the short sides of the bed. Overlap the corners connecting the rectangle. Make corners square and sides parallel. Next, attach each corner using two 4-inch screws.

3. Drive stakes inside each corner and saw tops off flush. Screw two 3-inch screws through the box into each stake.

4. Add hoops: Measure and mark where the tube straps will go. Start in a corner marking about 2 feet apart. Marks on the two sides have to be directly opposite one another.

5. Using 1-inch screws, attach the tube straps on the inside of the wood 1 inch down from the top.

6. Cut poly pipe into five 8-foot sections using pruning shears. Push poly pipe through tube straps and into the soil, making hoops. Even up their heights then fasten the other side of the tube straps with another 1-inch screw.

7. Lash furring strip or lath onto the bottom of the hoops with twine.

8. Attach the cover: Lay out the plastic, and then pull it evenly up over the hoops. Pull snug while clamping onto board or hoops using commercial clamps. You can also use homemade garden hose clamps on the hoops. To make them, cut a piece of old garden hose into 20 2-inch pieces, split them lengthwise, and slip the pieces onto the plastic and hoops.

9. Cut off excess plastic and fold the ends. Clamp the ends closed or secure the plastic on the ground with rocks.

HOOP GREENHOUSE DIAGRAM

Click to download enlarged version:

GREENHOUSE TIPS

Avoid pressure-treated lumber, which is toxic.
Face long sides southward for more sun.
Attach the cover when there’s no wind.
Pull the cover back on hot days so your plants won’t fry!
Choose cold-hardy crops (like carrots, potatoes or lettuce) to winter-over. When it freezes, cover them with an inside blanket or frost cloth.

GOOD TO KNOW

Regular 3-4 mil plastic sheeting lasts one to two years. Greenhouse 6 mil UV-safe sheeting lasts four to six years but costs more.
Lower-grade lumber works fine, but check each two-by-four for straightness. Fir lasts five to seven years outdoors and is cheapest. Cedar lasts 10 to 15 years but costs more.