So,what if you harvest a bunch willow, line them up in parallel lines, bend them into hoops, maybe run a support down the center.
I would then affix the plastic on the inside of the hoop
Crops inside the tunnel should be grown in containers,as willows are heavy feeders.
Or maybe the willows would be in containers,to contain their crazy roots.
In summer, the willows leaf out ,shading the interior.
So, grape vines grown up the outside of a conventional hoop house would probably be easier, but the willow idea occurred to me, so I thought i would share.
The only real drawback I see here is that quite often one can have ants on willows and then they'd drop on you while you're in there gardening
Also, don't count on plastic tied on willows to be able to stay safe in case of hail since willows are very elastic so I'd expect the entire structure to flex and bend every which way in such a situation.
I tried to bend willow, to make some kind of hedge, it didn't like it. But there are numerous kinds, so get the kind that does like it.
Or plant them close upon each other, in a line outside the hoophouse so they grow high "quickly". Willows are thirsty buggers though.
I like the concept. But I think there are certain issues to consider from my experience with a greenhouse and black raspberry. I am using the rasberries as a seasonal cover. I have a grape to help, but it's too small yet to affect the plastic. The plastic I used was from the hardware store, not specialty greenhouse stuff, though I hear the greenhouse stuff doesn't last either. This structure also has roll-up sides to save on plastic and allow circulation.
Now I have told you of where I'm coming from, here's what I noted:
1: plants grow. Obvious, but plastic doesn't. Also obvious, but you see where this can get a little awkward. Not only do plants grow taller and wider, they grow more branches and those can sometimes scratch and penetrate surfaces they are next to. If you leave enough space for the plastic to grow with the plants, it can also flap in the wind, banging against sticks, and tearing.
2: greenhouse plastic is made to be attached with wiggle wire or another multipoint attachment thing. Plants, however, get sick with some unbreathable surface attached to them so thoroughly...or maybe root growth can occur. If you attach it less, you end up with points of failure, flapping, and tearing because that plastic is weak.
3: depending on where you live, you may need to consider water or snow load + the strength of the trees. With a fixed structure you can shape it so most snow slides off, but if there's sag, snow will likely catch and then, you can either damage the structure or look forward to removing the snow regularly.
The rough willow branches will cause the plastic to tear sooner rather than later - more fodder for the landfill. Might want to consider just growing the right crop at the right time, as our forefathers did sustainably for countless millennia.
"A nation that destroys its soils destroys itself." FDR
"We can't solve problems by using the same kind of thinking we used when we created them.” Einstein
Though there are season extenders that don't degrade such as well placed stone walls built to capture and focus the sun's heat and light on your plants. But green houses and hoop houses can do a lot to extend growing seasons but the potential increase in waste is a downside.
For the willow idea I would be careful to pick a type that could be trained into a tree shape. Seems like you could grow them up as trees till they get thicker to form supports for the tunnel. Then the smaller branches could all be kept up above the tunnel. This would let sunlight in at a low angle but provide shade from the top. The tree willows could be grown to have relatively thick and stable posts.
I don't think this is something that could be done quickly. It would take time to let the willows grow and diligence to train them to grow the way you want. But it would be a cool structure was completed and you could grow beans up the willows and other planter under them. Not sure about the roots and competition but I would be tempted to grow beans and peas up it and greens and perhaps squash under it. Perhaps some root crops that don't mind shade too.
Actually I have plums in my high tunnel for posts and shade. They grow quickly from seed and thy can be top pruned to keep them from pushing up the cover and provide shade where I need it. Bonus is I get early plums and blossoms for the mason bees before the raspberries bloom so the bees stay in the hoop house. The framing for my hoop house is used portable garage frames.
There's a volunteer crab apple here that could have been made into a hoop house -- it grows these long gangling branches that form full hoops just from their own length and weight. (Seems to be its natural habit. It's an odd tree.) I've seen seed-grown apple trees that were real whippy, too, albeit more upright. Hmm....
yet another victim of Obsessive Weeding Disorder
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