Season Extension - Caterpillar High Tunnel

We previously looked at the construction of the caterpillar hoops for our soil beds.  In order to complete the caterpillar tunnel, we need to cover it with plastic.  The end product should look like this:

Our previously completed rib structure looks like this:

You can see from this photo that our soil bed is already filled with our growth medium mix, Mel's mix.  We have also filled in the cinder block holes with the soil mix as we'll be using these little spaces to grow the companion herbs, spices and flowers that attract good bugs and repel bad bugs.

You can see that the little cinder block holes are perfect for this.

We have our 55 gallon plastic water barrels in place to produce passive solar heating for the soil bed.  During the day, rays from the sun heat the water in the barrels.  At night, the water cools and as it cools, it radiates the built up heat back into the enclosed soil bed and heats the air.  This provides frost protection and allows us to extend the growing season.

Our first step is to ensure that the hoops are about the same height.  They don't have to be perfect, but it should be about the same height to prevent a camel tunnel.

Our next step is to get our plastic out.  You could use any construction plastic, provided it's clear.  You could also use specialized green house plastic, but that's expensive so we opted to go with construction plastic.  In theory you could use plastic thinner then 4 mil, but I wouldn't recommend it as it wouldn't provide much protection against radiation at night.  We decided to go with 6 mil plastic because it is heavy duty and should last a long time.  Remember you'll be installing the plastic and removing it again, twice per season so we want it to last.  I got the 20' x 100' roll as 20' was going to be wide enough to cover my hoops.  I had previously calculated we'll need about 26' wide, but slight tweaks to the hoops and spacing closer to the bed and the barrels allowed the 20' wide roll to work perfectly.

As you can see, 6 mil plastic is thick... very thick.  It allows only 60% light through and appears white, but it'll work.

Begin by rolling the plastic out next to the soil bed.  Be sure to keep it folded up as it comes off the roll.  This allows us to work with the plastic more easily.

IMPORTANT!!!  Remember to roll off more than enough plastic along the length of the bed.  The plastic is going to cover the bed and then slope down to the ground so some extra is needed.  It's better to have too much than too little.

Now pull the plastic over the hoop so as to position it in the center of the hoops.  Keep it folded as it came off the roll.  From this position, it allows us to straighten and tighten the plastic to the EMT ribs.

When properly positioned, there'll be a little sag between the ribs, but that's OK.

Now we need to secure our plastic to the EMT hoops.  There's many ways to do this, I'm sure, but the easiest and most efficient way to do it, is to buy these 1/2" EMT plastic clips from Johnny's.

They are well designed with an edge that tapers away from the plastic to minimize piercing of the plastic around the fasteners.  Additionally, they have a ribbed inside surface which prevents the plastic from slipping or pulling loose.  Though not cheap, these little babies are a major time saver so I recommend getting these.

Now go ahead and clip the plastic to the EMT ribs just to the side of the joint between the two pipes.

Once you have the center clipped, begin unrolling one side of the plastic down the ribs.

Attach a second set of clips half way between the first and the ground.

Repeat for all ribs and then unroll the plastic all the way to the ground.

Finally, another set of clips attach just about the ground level.

There should be some excess plastic at the ground level.  This can be cut away later.

Now repeat the process for the other side of the hoop.  Once the plastic is attached to the hoops, pull the openings on either end together in a V shape and stake it into the ground.

Here's the completed result:

It is important to note that practicality plays a larger role than theory.  This is a good example of that.  The reason I designed the tapered V was to break the wind and allow stronger resistance for the tunnel in high wind conditions.  In practice however, 6 mil plastic is thick and cumbersome to work with so pulling the tapered V together was not easy.  Additionally, when it rains, water collects in the tapered V creating a mess.  Access to the tunnel is also not as easy and the stake just doesn't quite seem to hold up so well when you are entering and leaving the tunnel on a daily basis.

This is where you'd have to weigh the risk of your tunnel getting blown away against the ease of use of the tunnel.  Creating a flat edge is easier to work with but risk high wind issues.  The choice is ultimately yours...

Soil Bed Preparation - Hoops

I had previously talked about our Row Caterpillars as part of the plan for Season Extension.  We believe that we could extend the growing season (which in Indianapolis is 181 days) by 4-6 weeks on either side.  That could push our growing season from 6 months to as much as 9 months!  So how do we go about constructing this tunnel?

There's a couple of things we'll need.

1.  1/2" EMT (Electro Metalic Tube)
2.  10' long rebar
3.  Hack saw
4.  Tape measure
5.  EMT Pipe Bender
6.  Sharpie

Begin by measuring out 5' (half way) on the first piece of rebar.  Use the hack saw to cut the rebar at the measured cut.

Now take all subsequent pieces of rebar and simply line one end up with one of the first cut pieces and cut at the matching end.  The rebar is going to serve as our anchors for the hoops.  We will knock the 5' pieces into the ground until 3' is underground and only 2' is left protruding above ground.

Now that the rebar is cut, it's time to measure the EMT.  The pipe bender has a 10 degree bend angle line, and that's what we're going to use to get our hoops bent.  If we consider one half of the hoop (1/4 circle) the direction change from vertical where it will start at ground level to horizontal where it will meet the other end, is 90 degrees.  Given 10 degree bends, we will need 9 bends in order to make the half hoop.  Given the length of our EMT, we will make these bends every 6" starting at 12" to allow some middle extension to bring the two sides together.  Using the measuring tape, mark at 12", 18", 24", 30", 36", 42", 48", 54" and 60".



Now turn to the other end of the EMT pipe and measure off 18".  This is 18" we're going to cut off to lower the tunnel so as to not have any excess air inside.  Remember that any air inside the tunnel needs to be warmed at night by the passive radiation of the water barrels.  The less air we have the more effective the barrels will be so it's important to keep the tunnel size as small as is practical while still fitting all the components inside.

Now take your other 7 pieces of EMT and align them on the ground with the piece we just marked.

Now, using the Sharpie, simply draw across the other pipes at each mark in order to mark them quickly and efficiently.

Next we position each piece of EMT into the pipe bender in turn.  Align the marker with the Sharpie mark on the short side of the pipe.  I can't stress this enough.  Bending pipe is about leverage so you do NOT want the short side to be the side you're bending.  Once aligned, simply bend the pipe until the longer side aligns with the 10 degree mark.  It's also easier to align when you have the longer side here.  Don't worry about getting the bend exactly at 10 degrees.  By the time you've made 9 bends, I guarantee you your hoop is going to bend 100 degrees plus and you'll have to bend back a little to get it to 90 degrees properly.  Don't worry... it doesn't have to be perfect.

One thing to ensure is that you keep the bent section of pipe level off the ground.  Failing to do so, will cause your bends to form a spiral which isn't good.

Continue until all your EMT has been bent to 90 degrees.

Now cut off the 18" piece at the bottom of the EMT.

After placing the 6 plastic 55 gallon barrels on the north side of the raised soil bed, we hammer the rebar into the ground until 3' is underground and only 2' protrudes above ground.  These form the anchors for the EMT pipes.  One anchor is at each of the 4' sides of the bed.  Given that we're using 9 cinder blocks on the 12' side of the bed, the other two anchors are driven into the ground between the 3rd and 4th cinder blocks as well as between the 6th and 7th blocks.

Once you've driven the rebar into the ground, slide the EMT pieces over the top.  Connect the ends over the bed with a simple coupling connector.  Once the 4 ribs are connected, your caterpillar frame is ready for the plastic cover, but that's a topic for tomorrow.

Joint us again tomorrow as we look at covering the hoops with plastic to complete the caterpillar tunnel.

Seed Starting Shelves

A large part of season extension is in starting seeds indoors.  For this purpose, I'm going to be starting seeds indoors this year and see how the transplanting goes.  I don't have all the tools for full season extension caterpillars yet, so this is a quick, easy and cost effective way to get a jump start on the growing season.  Once the beds have full season extension features, indoor seed starting will help extend even further into early spring.

For starters, I wanted to find a stainless steel shelving system that would hold up for years to come.  I looked around and the Seville SHE14305-5 the best.  It can be found on Amazon here:

http://www.amazon.com/Seville-Classics-SHE14305-5-Shelf-Storage/dp/B001A0VYZY

The shelve arrived and my daughter Jill and I went about assembling it.  Jill's only 8, but she's my big helper in the garden. :-)

The rack in the box.

Once we unpacked it, it was a pretty clean and simple set of components.

There are no tools other than a small and thin hex spanner for getting the wheels attached.

The assembly was painless and straight forward.  I will just note that you need to be aware of the cylindrical corners of the shelves.  They are tapered to make them easier to position properly on the vertical supports, but if you lower the shelve the wrong way around, you'll spend some time trying to figure out why things don't fit.  Basically, if the parts don't just snap and slide together almost effortlessly, you're doing something wrong.  In our case, we assumed the shelves would have the larger lip side facing up, but that was not the case, so it took us a couple of minutes to figure out the problem.  Total assembly time should be about 20 minutes.

The ONLY tool we used, and it really isn't needed, was my rubber mallet to gently tap the shelves to the proper level.

The shelves are ready.  Now we need to get the lighting to go with it and the seedling trays to fit before we begin.

Seed Starting Tray

For the indoor seed starting, we had previously assembled a stainless steel shelf.  Now the next step is to get the starting trays that will rest on the shelf.  I'm trying out this kit from Burpee.

When you open it, the kit contains a couple of components.  The first component is a seed chart.  Since all seedlings look pretty much alike, this would be useful in helping identify what we planted where.

The next is a thin plastic elevation panel.

The plastic is VERY thin and in our case, some of the legs was crushed in transit from the store.  They pop back easily enough and since we're not supporting heavy weight, the flimsy feel can be forgiven.

The next piece is the tray itself.  This particular tray contains 72 pods.

Each pod contains a small compressed pellet.  The pellets are made of coconut material and should expand within seconds after being watered.

When we peer down into the pod, we notice that the bottoms have holes.  This is for the self watering function to keep the growing medium damp.

The next component is the self watering mat.  The mat is nylon on one side and soft spongy material on the other.

The final component is the water tray.  This is also very flimsy.  I'm a little more concerned about this one's flimsiness because we cannot afford any leaks or the self watering feature won't work.

The assembly sequence for use is simple.  Start by placing the elevation tray in the watering tray.

Now evenly place the watering mat over the elevation tray, ensuring that the watering mat's sides touch the watering tray on both sides.

Now the seedling pods is placed on top of the watering mat.  Water is kept in the watering tray which is wicked up by the watering mat.  The seedling pods being in touch with the watering mat, absorb the needed moisture and keep the growing medium moist.

Spacing of the seedling tray on our shelf seem to fit nicely with room to spare.  We can fit 4 trays on our shelf which would give us the ability to grow 288 seedlings at a time.