That is cool!

In case bricks aren't sturdy enough, you could opt for tent pegs. Of course those are harder to remove.

There is an easy method (based on the construction of tunnel tents) of making these quick-hoops into self-supporting structures that you can easily tilt up or pick up and carry away, if you're interested.

Maggie --- no, it's supposed to be warm.

Roland --- The trick is not to tear the fabric --- it's very delicate. We have tent pegs on the ends (although one of those actually tore out of the ground in the heavy wind episode), but I can bunch the fabric up there to make it less likely to tear.

I agree that tents are the place to look for design ideas. What would you recommend along those lines?

The simple way to make a hoop tunnel that has some structural integrity is as follows;

• Make hoops by bending a length hoop material and tying a string at both ends. This way you get a hoop without having to push them into the ground.
• Tie the hoops to two pieces of rebar like you've used now, with a suitable distance between the hoops.
• Put a hoop over the ends of the rebar at both ends. These hoops will lie horizontally and form the ends of the "tent".
• Fasten a length of cord to the middle of one of these aforementioned horizontal hoops. Now tie the cord around the middle of each hoop in sequence, making sure that the hoop is vertical when the cord is taut. Tie the cord to the opposite horizontal hoop to finish the basic structure.
• Spread your fabric over the hoops, tighten and fasten it.

This should make a tunnel that is structurally a whole (albeit a rather flexible one). Adding guy wires from the center of one hoop to the ends of its neighbours would add structural stiffness, but might interfere with the plants

As to the materials;

• Use 1/8" fiberglass rods for the hoops. They will last much longer in the sun than e.g. PVC pipes, and they won't rust like steel does. The minimum bend radius for such rods is about 100x their diameter.
• Standard row cover material seems to be spunbonded (non-woven) polypropylene. Nonwovens are generally not very strong. If you can find a woven one, it will probably be stronger. But like all thermoplastics, polypropylene is broken down by ultraviolet light.

If you would stretch a light weight woven fiberglass cloth over the hoops, and paint it with polyester resin, you'd get a pretty much translucent (at least to the eye, don't know about the full spectrum) material that is very strong, wind- and watertight and long lasting. (About 15-20 years before the polyester breaks down, at a guess when using a resin with a UV inhibitor. The fiberglass itself does not break down in sunlight.)

It is possible to buy ready-made fiberglass/polyester translucent panels, either flat or corrugated and nail it over wooden arches. Would be thicker and therefore heavier than the DIY solution, though.

Does the fabric HAVE to be that delicate? At work, we stake down 1/2" thick wool blankets over the outdoor crops when it's below freezing.

If you don't want to change fabrics, maybe you could sew eye rings into the fabric along the edge. That way, you could use stakes without worrying about tearing the fabric.

I should give you all a little more data on the fabric. Eliot Coleman's experience (and mine) has been that you need to use an extremely light weight fabric if your goal is to put it up and forget it. They sell row cover fabric that is significantly thicker than this, but the problem is that it blocks too much of the sunlight and can actually cool the soil. The alternative is plastic, which is easier to work with, but you have to go out and vent that even on moderately warm days and you also have to water under it or you get dry, baked soil. Blankets, of course, are just for night use, so wouldn't help me start early spring crops like lettuce that need 24 hour protection. Really thin row cover fabric solves all of those problems so elegantly that I feel like it's worth working around its delicateness.

The other thing you have to consider when planning quick hoops is getting into them easily and making them easy to assemble and disassemble --- these aren't supposed to be permanent greenhouses, but lightweight structures that can be used to get plants off to an early start then moved to the next row to do the same for the crops there a month later. You also want to refrain from putting any cross supports on the ground since that will make it tough to weed/mulch/etc. While Roland's solution sounds like it would stand up to a gale, it also sounds like it would be so complicated to open up that I'm unlikely to take the lid off when I just want a quick salad.

I have considered a plan that's a bit like Roland's where you use PVC elbows and more pipe to make a solid frame around the bottom that connects to the hoop, but that is going to get a lot pricier and harder to put together than this version. We have the PVC pipes slipped over rebar pegs right now, which makes the quick hoop very easy to dissasemble but holds the hoops together very well --- it was only the fabric that blew away during the storm, not the hoops. My conclusion is that the important thing is to make it so that no wind can get up under the fabric.

I like Edward's solution of sewing eye rings along the bottom edge. I'm not sure this fabric is strong enough to take even that, but I could envision some sort of heavier duty fabric bottom edge that could be attached to the row cover. I'm going to have to ponder something that could be added down there pretty quickly (so that I won't mind doing it over and over when the fabric wears out every year) and reused.

You might be able to make the edges of the row cover stronger by folding it a couple of times and then melting the layers together with a flat-iron. An electric flat-iron should be able to melt polypropylene if you set it between the temperature for wool and cotton. Don't overdo it; molten plastic can make quite a mess. You might have to do it in several steps; you'd have to experiment.

You could also embed another material in the row cover this way, I think. But take care not to make the edges too stiff, or the row cover might tear at the boundary between stiffened and unstiffened material.

If you don't have a flat-iron, or if you don't want to use it for this purpose, you should be able to find or make an old-fashioned flat-iron that you can heat up on the stove. But getting the temperature right in that case might be tricky

This is brilliant! That definitely sounds like a quick and dirty way to strengthen the edges. Now I need to decide whether I'm going to attach the edges to something, or maybe turn the strengthened edges into a pocket that I can slip the rebar into for ease of opening and closing.