In this tip:
- A)# Greenhouse with (bamboo) sticks
- B)# Greenhouse with iron wire bows and thick iron pens.
For growing early lettuce, summer carrots, leek and so on you can use a tunnel greenhouse made of transparent corrugated plate. Also useful above late endive, leek or lettuce.
This greenhouse is very useful:
- Easier to make than a greenhouse made of wood or bricks with plastic foil or glass plate on it.
- Movable to a new place in your garden or over small plants.
- Easily to dismantle. The corrugated plate can be used as a roof.
- The lifetime of the greenhouse is long, more than 5 years.
- Not very expensive; about €20.00 for plate, iron wire, pens and hose.
At each end of the tunnel greenhouse there is a “closing plate” (40 x 40 centimeters, 1 ft 4 inch square) made of perspex or corrugated plate. Perspex can be sawed out or scribed and broken off. Corrugated plate can be cut using sharp scissors. Old corrugated plate can be sawed carefully using a blunt wood hand saw.
About the closing plates:
- When using closing plates of corrugated plate, the tunnel greenhouse is more airy and cooler (see photo above).
- When using perspex closing plates, it is warmer in the tunnel greenhouse. The greenhouse can be used in winter and early spring. Put a (bamboo) stick against the closing plate for a good closure.
Making the tunnel greenhouse is described below;
- Make a tunnel greenhouse with bamboo sticks or
- Make a tunnel greenhouse with bows made of iron wire.
Each tunnel greenhouse has closing plates of corrugated plate or perspex.
A)# Greenhouse with (bamboo) sticks.
- (Bamboo) sticks 60 to 90 centimeters (2 to 3 feet) long, 8 sticks needed.
- Corrugated plate (PVC or PET), width 66 centimeters (2 ft 2 inch). The hills; pitch 32 millimeters (1 1/4 inc), height 9 millimeters (23/64 inch). A plate of 183 centimeters (6 ft) long costs about 17 Euros.
A2) Building up
- Put 2 or 3 bamboo sticks slanting in the garden soil.
- Lay one long side of the corrugated plate against these sticks.
- Bend the corrugated plate round ( n-form).
- Put 2 or 3 bamboo sticks slanting in the soil against the other long side.
- Put a closing plate at each end of the tunnel.
- When needed, put a (bamboo) stick against the closing plate (on the outside).
Disadvantages: This greenhouse can be blown loose at strong wind. To open the greenhouse it has to be dismantled and the corrugated plate must be put down somewhere.
One can improve this greenhouse using a piece of clothesline wire.
- Make a loop, a knot and another loop in a piece of wire. Make 2 of these.
- Bend a corrugated plate in a tunnel shape (n-shape).
- Put one rope with loops and knot around the tunnel of corrugated plate.
- Tie the long part of the rope at the small piece of the rope between knot and loop.
- Repeat this with the other piece of rope.
- Shift or turn each rope;
- until each loop is near a long edges of the corrugated plate
- until each piece of rope is about 40 centimeters (1 ft 4 inch) from the end of the tunnel.
- Put the greenhouse at the intended place in the garden.
- Put a (bamboo) stick slanting through each loop, like this: \n/ .
- Put 2 (or 4) bamboo sticks between the ropes, slanting in the soil;
- Put the sticks slanting against the tunnel ( /n\ ).
- These sticks provide an extra fixation to the earth.
- These sticks keep the long sides of the tunnel straight.
- Put closing plates in the soil at both ends of the tunnel greenhouse.
- When desired, put a stick (at the outer side) against each closing plate.
Advantages: Stronger construction and the greenhouse is movable (carefully).
Disadvantages: Harder to make and there are wires on the soil under the tunnel.
B)# Greenhouse with iron wire bows and thick iron pens.
Put iron bows over bent corrugated plate to have a tunnel greenhouse that stays in shape.
A tunnel greenhouse with iron bows, opened or closed.
A bow made of double iron wire. It fits over a bent corrugated plate.
The long sides of the plate fit in the U-shaped parts (blue white arrows).
Two “loops” (red white arrows) are used to fix the tunnel to the soil.
Put iron pens in these loops to fix the tunnel to the soil. These pens are also used to keep the tunnel open. More info later in this tip.
Below there is info about thick iron pens and 2 tunnels;
- B1) thick iron pens
- B2) tunnel with bows of thin iron wire (2.5 millimeters, 1/10 inch)
- B3) tunnel with bows of thick iron wire (3 millimeters, 15/128 inch).
My experience: Bows made of double thin iron wire are very rigid. Thin iron wire (2.5 millimeters, 1/10 inch diameter) is for sale in many shops. The bows are easy to make.
Thick iron wire (3 millimeters diameter, 15/128 inch) is for sale in special shops or on the internet and harder to bend.
So bows made of thin iron wire are the best.
B1) Making thick iron pens
Thick pens are used to anchor the tunnel greenhouse to the garden soil and to keep the tunnel open. Below a description of making these thick pens.
- Pieces of reinforcing steel rods of 7 or 8 millimeters (9/32 or 5/16 inch) nominal diameter. For sale at a scrap dealer or at a shop for construction materials.
- Pieces of aquarium hose, about 9 millimeters (23/64 inch) inner diameter.
- Saw the reinforcing steel to about 70 centimeters (2 ft, 4 inch). Use a bench vice and a hack saw (or use a steel bolt cutter).
- At each pen, bend over about 10 centimeters (4 inch). Use a bench vice.
- Put a piece of plastic hose over the short end of a thick iron pen;
- Fix the pen in a bench vice, with the short end (the handle) up.
- Put a piece of hose over the handle part until the beginning of the curve.
- Use a hammer to hit on the free end of the hose; the hose follows the curve.
B2) Tunnel with thin iron wire
At this tunnel, thin iron wire (2.5 millimeters (1/10 inch) diameter) is used to make a bow. But single iron wire of 2.5 millimeters is too thin to make a rigid bow. When using 2 wires next to each other you get a rigid bow.
There is a piece of thin hose at the U-shaped parts against damage of the plate.
Each bow has 2 loops just above the soil. Push thick iron pens through these loops to fix the tunnel to the soil. Info about the thick iron pins see chapter B1).
A short tunnel greenhouse with 2 bows of double iron wire. (each bow has a “handle” made of nylon cord, easy to lift the tunnel).
To keep the tunnel “floating above the soil” you can do this:
- At each corner of the tunnel greenhouse, act as follows (see white arrow):
- Put a thick iron pen in the soil, with the handle about 20 centimeters ( 8 inch) above the soil.
- Put the piece “between loop and bow” on top of the handle of this pen.
- Put another iron pen through the loop in the garden soil.
- In this way the tunnel is fixed a little above the garden soil.
- At each corner the tunnel can be raised or lowered;
- Higher: pull both iron pens higher above the soil.
- Lower: push both iron pens deeper in the soil.
- This method is very easy and useful.
Remark: when the piece “between loop and bow” is very short, there is little room for the second iron pen to fit in the loop. Then do as follows:
The lower iron pen has no aquarium hose. So this pen is thinner. The top pen fits better in (through) the loop.
You can use the same procedure to put the tunnel open at 1 long side:
- At the “closed” long side, thick iron pens are through loops in the garden soil (at the outer side of the tunnel), see red/yellow arrow.
- The open long side stays open using 2 iron pens.
- The top iron pen is in the loop and slanting in the soil.
- You can do this near both ends of the tunnel greenhouse (or only in the middle of the the greenhouse).
You can use iron pens “with no aquarium hose” too.
To keep a tunnel far open, this procedure does not work well; the iron pens are too short or they are too shallow in the soil.
You can fix one extra ring to the bow (see red/yellow arrow).
At each outer bow, put the handle of a thick iron pen in the extra ring. Put the iron pin into the soil until the right depth.
Warning: don’t put the tunnel greenhouse in this far open position at windy weather; the tunnel greenhouse can be damaged or blown loose.
On most “construction photos” below, the corrugated plate has a milky color. This is to clarify the construction. The greenhouse over plants is always transparent.
- Iron wire, thickness 2.5 millimeters.
- Thin plastic hose, 3 millimeters inner diameter, to be sold in an animal shop.
- Detail info about the iron wire.
- Tools: pliers and one bolt of 8 millimeter (1/3 inch) diameter.
- For a corrugated plate of 65 centimeters (2 ft 2 inch) wide, you need about 200 centimeters (2 meters, 6 ft 7 inch) of iron wire.
- Cut 200 centimeters (6 ft 7 inch) of iron wire.
- Bend the iron wire in the shape of the drawing above.
- The bent iron wire has 2 rectangular (straight) angles.
- Length of each “leg” is 67 centimeters (2 ft 2 3/8 inch).
- Length of the central part is 66 centimeters (2 ft 2 inch).
- Clamp the iron bolt in a bench vice.
- Bend the wire; make a loop out of each rectangular (straight) angle.
- Bend the wire around the iron bolt.
- Bend until the loop has the right shape (see photo above).
- Take the wire from the iron bolt.
Use your hands and pliers to turn the loop into its desired shape as shown on the photo above. Below a step by step description;
- Use garden gloves or work gloves.
- At each loop execute as follows:
- Hold 2 free pieces of wire in one hand.
- Put the loop in the pliers.
- Use the pliers to turn the loop 1.5 or 2 turns. Meanwhile hold the 2 free pieces of wire in the other hand (hold with thumb and fingers).
- (The loop on the photo above must be turned “left hand” (counter clockwise))
The result; a twisted loop.
The distance between the loop and the 2 straight pieces of iron wire should be about 1.3 centimeters (0.5 inch). Is this distance too short, turn the loop 1/2 or 1 turn more.
Repeat these steps at the other rectangular (straight) angle to make the 2nd loop in the iron wire.
- The distance between the loops is about 58 centimeters (1 ft 11 inch). That’s about 7 centimeters (3 inch) less than the width of the plate. The remaining “loose” straight pieces of iron wire are about 60 centimeters (2 ft) long.
- Cut two pieces of thin hose, each about 28 centimeters (11 inch) long.
- Slide each thin plastic hose over one loose end of the iron wire up to the loop.
- Bend the loose end of the iron wire (with plastic hose) in a curve. See photo above.
- Bend the other loose end in a curve too.
- In the center there are 1 continuous iron wire and 2 loose ends of iron wire. The loose ends are about 25 centimeters (10 inch) “double”.
- Twist 1 loose wire (between 2 yellow arrows) around the continuous wire.
- Then twist the other loose wire (between 2 red arrows);
- Turn this piece of wire around the 2 already twisted wires.
- Turn this piece of wire (“left or right”) so it “fits well” over the 2 already twisted wires.
- This photo shows how 2 pieces of iron wire are turned around 1 iron wire.
- Put a tie wrap (cable tie) over each end to keep the 3 wires turned together. Cut the loose ends of the tie wraps.
- Bend the whole in this curved shape.
- Bend the ends of the bow in a U-shape to fit it over a bent corrugated plate.
The bow is ready for use. To put the bow over a curved piece of corrugated plate, (or to release the bow) do as follows;
- Shove the bow over the curved plate.
- Or bend one end of the bow (back) to a |_ shape, put the bow over the curved plate and bend the same end of the bow in a U-shape again.
Putting an extra ring at the bow
You can put one extra ring to bow. With this ring on the bow, you can put the tunnel greenhouse far open at one long side.
You can put 1 thick ring on the bow. See red/yellow arrow on the photo above. Only 1 ring is needed per bow. For 1 tunnel greenhouse you need 2 bows with an extra ring.
Put the bow with ring correct over the curved corrugated plate (or turn the tunnel greenhouse). The extra ring must be at the opening side of the tunnel greenhouse (e.g. at the sunny side).
You can saw these rings from thick plastic hose or from 3/4 inch electric conduit pipe.
- Use thick plastic hose or conduit pipe.
- Use a hack saw to make the ring out of a plastic hose or conduit pipe..
- The photos above show the size of the ring.
Fixing rings to the bow
You can use narrow tie-wraps (cable ties) to fasten the ring to the bow. Below the procedure for the thick hose ring (fixing a ring of conduit pipe is just as easy).
- Put the tie wraps “crosswise” to fix a ring on a bow.
- Use pliers to tighten the tie wraps.
- Cut the remaining parts of the tie wraps.
- The handle of an iron pen fits well in the eye made of thick hose.
Warning: the cut ends of the 2 cable ties are sharp. There are various ways to work safely when putting the bow over a bent plate;
- Wear work gloves when bending the end of the bow with the ring on.
- Or use sand paper or a file to make the tie-wrap ends smooth.
- Or use a special way to put the bow over a curved corrugated plate (see below);
- Have the bow in this form. The left side end of the bow with ring remains in the U-form. The right side end of the bow is bent in a _| form.
- Put the bow over a curved corrugated plate;
- Put the left end of the bow over the plate.
- Put the bow over the curved plate.
- Put the right end over the edge of the plate.
- Bend the right end from a _| form into a U-form.
- Put the bow over a curved corrugated plate;
1] A bow of twisted thin iron wire (diameter 2.5 millimeters, 1/10 inch) is rigid enough to make a greenhouse tunnel.
2] Untwisting the bow:
When needed you can shove the tie-wraps aside and untwist the iron wires of the bow. See photos above. You can do that when making the bow longer or shorter so it fits better over the curved corrugated plate.
After this, twist the wires again and shove the tie-wraps over the ends of the wire.
3] Making longer “arc loops” in the iron wire.
You can make the arc loops in the iron wire longer. This eases bending the end of the bow in a U-shaped form.
You can put a loop of nylon rope on each outer bow. This eases lifting, moving and putting down the greenhouse.
5] Water in plastic hose
There can be condensed water in the thin plastic hose of the bow. This can make the iron bow rusting.
You can use side pliers to cut a little piece out of the hose. Condensed water can flow out now.
6] Tunnel ready for use:
This photo shows a short tunnel with 2 bows, ready for use. At a long tunnel, 3 bows are used; 2 near the ends and 1 in the center.
7] Storage (not) too warm
You can store not used tunnels on your garden soil.
Store 1 or maximal 2 tunnels over each other on the garden soil.
When you put 3 or more tunnels over each other, the plates get brown and are deformed by sun heat.
B3) Using bows of thick iron wire
This is my first design. Using thick iron wire. This construction is less useful, I think.
Bows made of thick rigid iron wire. In each bow there are loops.
The greenhouse is fixed to the soil using thick iron pens through loops in teh bow.
There is a (cut open lengthwise) piece of garden hose to prevent damage of the edge of the corrugated plate.
At the “open” position, the handle of an iron pen is put in an extra loop in the bow. This is near both ends of the tunnel greenhouse.
(you can also put the tunnel in the open position using 2 thick iron pens, that’s much easier).
- Thick iron wire, about 3 millimeters (15/128 inch) diameter.
- Pieces of plastic garden hose.
B3c) Making bows (bending thick iron wire)
- Start with a piece of thick iron wire, length 130 cm (4 feet 3 inch).
- Use tongs (pliers).
- Bend the thick iron wire in the shape as on the photo’s above.
Remark: The loop in the short end of the wire is not needed, you can keep the tunnel open or high as shown on the photo above (other type of bow).
Making bows (continued)
- Make a “top loop” in the bow as shown on the photos above.
- Bend the thick iron wire in a curved shape.
- Check if the bow fits well over the curved corrugated plate.
- When the bow is too large, give the top loop an extra turn to shorten the bow. You can use a broomstick when turning..
Making bows (continued)
- For one tunnel greenhouse you need at least:
- Two bows of thick iron wire with eyes and loops,
- Four (4) pieces of plastic hose,
- Four thick iron pens, made out of pieces of concrete iron rods. Each thick pen has a handle.
- Use scissors to cut each piece of plastic hose in the longitudinal direction.
- Bend the corrugated plate in a tunnel shape.
- Put a bow over the plate.
- Put a piece of plastic hose (cut in length) over the edge of the corrugated plate, in the space between plate and bow.
- Is the bow too big or too small, turn the middle eye of the bow clockwise or counter clockwise. This turning makes the bow longer or shorter.