Hoop Dreams

Last week I went to a workshop on high tunnels, or hoop houses as some folks call them.  It was sponsored by the University of Minnesota and featured several speakers talking about the ins and outs of season extension using this sort of technology.  I use 'technology' loosely, as the ideas behind high tunnels (and low tunnels, for that matter) have been around for decades, if not centuries.

It was a really great workshop, and it got my mind abuzz with all sorts of possibilities.  I'm planning on trying a bit of low tunnel action this spring, in fact I've got all my metal hoops and woven cloth ready to go.  I just need a nice day (when I don't work!) to set it all up, and transplant my lettuce seedlings.  Maybe plant a few radishes and arugula.  And spinach.  And kale.  You get the drift.

After all the speakers were done we took a tour of the university's tunnels, located in Lamberton.

These tunnels have roll-up sides.  Most tunnels are manual roll-ups, but these were thermostatically controlled.  The controls added another $1400 on to the cost of the tunnel, but if it saves a roasted crop due to someone's negligence, it may be worth it.  Temps in these tunnels can spike up to 100 degrees just a few short hours after sunrise, so you really have to be on the ball with the ventilation.

Here's the thermostatic controls (I think).

The inside of the tunnel was lovely.  This one had five rows for veges.  The speakers explained that there are three zones in these tunnels -- the outer cooler zone, the intermediate zone, and the center warm zone.  The cooler zone is along the edges by the vent flaps, and that is where they plant cool season crops.

Like these!  To help protect the plants even further in the cold weather, a low tunnel can be put inside the high tunnel.  In his book 'The Winter Harvest Handbook', Eliot Coleman (regarded as an expert in season extension gardening) highly recommends this method for growing veges during the colder months.

Little lettuces, I think.

All of the speakers said that even though it's not ideal, it's pretty much a necessity to use black plastic mulch to control weeds.  Weed control is a big issue in high tunnels, which makes sense.  What's good for the goose is good for the gander.  If your veges will love living in a high tunnel, imagine how much the weeds will love living in one!

A big benefit to high tunnels is the ability to control irrigation.  Here is the water set-up as it enters the high tunnel.  It gets sent down a main PVC pipe, which is connected to drip tape.

The drip tape is run just on top of, or just buried under the soil along the planting beds.  Beds are either 18 or 24 inches wide.  The pathways in between are usually covered with newspaper and straw.  The drip tape has holes along its length, kinda like a soaker hose, but more flimsy.  Most people don't re-use these tapes.  Rather, they throw them away and buy new every year.  They said that after awhile the holes clog up, either from soil or from water sediment.

They did mention that if you're using hard water from a well, you'll probably want to install an in-line filter somewhere along the line, otherwise these tapes will clog up really fast.  I asked a guy about the water usage involved and whether a home pressure tank could handle the quantity, and he said easy peasy, unless you have a monstrously huge tunnel with lots of tape.

At the ends of the center and intermediate beds were these pipes stuck into the ground.  Another observer and I figured they must be for installing trellises.  The speakers had made a point of telling folks not to use the structure of the high tunnel as an anchor for trellises, as the weight of all the tomato or cucumber vines would quickly collapse the frame.  These pipes make a good anchor for a 4x4 post, which could support a system of trellises along the tunnel's length.

Several of the speakers spoke of their experience with tunnel collapse.  Sturdy construction is key, especially with the end walls.  Timber framed end walls are strongly recommended, as well as a good wind break.  Setting the end posts (if not all the posts) in concrete isn't a bad idea.

There was so much information shared, much too much to relate here.  Season extension shows so much promise for us here in the frosty upper midwest, and could do so much for the local food momentum.  Our state agricultural department even has a cost-share program (called EQIP) to help farmers install high tunnels on their property.

Like I said, my mind is abuzz.  Time to digest these ideas and see what's plausible in the immediate future.  Do I really have the time to manage a high tunnel?  I don't know.  Probably not.  But it would be fun to try.