P-P-P-Put up a polytunnel!

Back when it was shiny and new.

We're now just over a year into our experience of polytunnel growing. Definitely a success. Very happy that we decided to go for one. It extends the growing season considerably for a number of crops, and expands the range of growing possibilities.

If you're a grower of veg living some place with lots of wind or short summers and long winters, a polytunnel is a great option.

Polytunnel vs greenhouse (or glass house) is a classic debate. What it really boils down to is cost. To cover a given area, the polytunnel comes in a lot cheaper, even if you go (as you should) for the highest spec you can afford.

The chosen spot.

Before even getting to the tunnel, selection of a site is key. A bit of shelter is helpful, if available, but direct sun is probably more important. The ground doesn't have to be exactly level, but shouldn't be too far off, and there has to be sufficient space on all sides to work when putting the thing up.

Choose a tunnel

As usual, we did quite a lot of research before selecting a tunnel. There are a lot of options out there. For us, strength was right at the top of the desirable qualities list, as we knew it would have to stand up to some very strong winds here, particularly through the winter. That helped to narrow the field for a start. A good rummage around through gardener's forums etc. online soon flagged up some brands to forget about and a few to look more closely at.

Putting it up.

This leads directly into the nitty gritty of what the tunnel is made from and how it's anchored and, again, there's considerable variability on these points. Gauge of steel used and tube diameter of the hoops, how many sections they come in, what cross members are used, anchoring system, thickness of cover plastic - all affect the strength, durability and, of course, cost of the unit.

Cost, naturally, came next on our list of considerations. We're always looking for value, but will pay what we have to, to get good quality. There's no point in 'saving' a third on something that will only last a quarter as long.

Securing the cover to the frame.

Our final criterion was ease of erection. There are quite a few different systems for securing the cover to the frame, some more, some less user-friendly. Getting the cover on really snugly is a critical determinant of its lifespan, so we wanted to go for one that would give us the best chance of getting it right on the first attempt.

Put it up

Our chosen tunnel is 20 x 8 feet, with screw anchors at each hoop base and a clever wire-clamp system for securing the cover to the frame. We put it up over 2 days, the frame on the first and the cover on the second. It's a huge sheet of plastic, so it's vital to do this on a windless day!

The first critical step, and one that was surprisingly tricky, is getting the positions of the anchor points correct, so that all four corners are exactly 90° square. It's really important to get this right, so mark it out with stakes and string, then check and re-check using the Pythagorean 3-4-5 method on each corner. For those whose geometry might be a little rusty, the length of the sides of a right angle triangle are always in the proportions of 3-4-5.

Finally: the door.

Putting anti-hotspot tape over the steel frame everywhere it will contact the plastic is a simple way to extend the life of the cover: don't skip this out.

Make sure you have as many helpers on hand as necessary to get the cover on nice and tight. The design we chose was okay for two people to put up - one to hold the plastic while the other did the clamping - but I've heard that other types, such as the traditional trench-fixing, are better done with at least three.

So, two day's effort to finish putting up our very first polytunnel - not bad. The second would obviously be easier with the experience, but I'm in no particular hurry to do it again.

The finished article fits in nicely.

I must confess that there was a certain amount of trepidation in the air when the first of the big winter gales struck, but that tunnel is rock solid and has so far stood it all without complaint. Well, almost without complaint. The one thing that couldn't quite take it is the velcro fastening on the vent panel cover at the back end of the tunnel (visible in the photo above). No matter how firmly we press that on, it will blow off with a strong wind pressing against it. My solution has been to screw a couple of 'storm boards' into the aluminium frame across the vent. It does the job, but that fastening seems to me to be the one design flaw in the whole setup. Perhaps a zip fastener would have been a better bet.

Next time: Growing in the tunnel
Extend your growing season and range.

Digging a Hügel

Couldn't have known what a big job it would be.

The single largest task we had planned for this spring was creating a large (about 12 x 4 metres, or 40 x 15 feet) new vegetable bed down in the bottom paddock.

We're nearing the end of our rolling programme of covering large areas with black plastic each year, for digging new beds the following year. The ground down there is quite heavy with clay, borderline boggy. The original intention was that it should be this year's potato bed, but when I started digging it, back in February or March, I soon concluded that it was far too wet and stony to be ready in time for planting potatoes! We found a better spot for the tatties and put this one on the back-burner for a little longer.

Happily, at just this time, we heard about Hügelkultur (literally mound- or hill-culture). This is a land management technique long practised in parts of Germany and Eastern Europe, in which marginal land is made cultivable by creating mounds of wood, woody waste from around the garden, plant and grass cuttings: basically whatever organic material is handy, with compost and soil over all. The result is a bed with a decaying core of organic matter that acts as a moisture store, while gradually breaking down, enriching and contributing to the soil.

Typically, the material is simply piled up on the surface of the ground, over an area of about one by two metres, to a maximum height of approximately one metre. In our case, the area we wanted to cultivate is considerably larger (of course, we could have just created a series of small mounds), and is also very windswept. Although we have planted hedges to break the wind, it'll be a few years yet before the shelter is really good and in the meantime we can't get into vertical gardening.

By this stage I was starting to realise the scale of it.

We decided to modify the method to suit our needs, inverting our Hügel and embedding it in the ground, so I started by digging a large trench. The first six to eight inches weren't too bad, coming up with the spade as hefty soil blocks, with some stones scattered throughout.

Couldn't have done it without the fishbox soil sifter.

Then came the 'stone zone'. A layer of another six to eight inches so packed with stones as to be impenetrable to spade or fork. I suppose at one time, 9000 or so years ago, this was the bed of a glacial meltwater runoff.

We had just invested in a Mantis tiller, which proved to be the very tool for the job. With that, I was able to gouge out the stone zone layer, into piles of earth and stone the we could shake through our homemade fishbox soil sifter. The soil was thus kept to go back on top and the stone added to our ever-increasing mound of rubble in the bottom corner of the garden.

Probably couldn't have done it without beer either.

Once underneath the stone zone, the ground was again penetrable to the spade, allowing me to dig out the deepest, central portion of the trench, down another 12 inches or so.

That's where the trench met the level of the ground water, and soon there was water pooling in the bottom of the trench, even though we were weeks into an unusually dry spell of weather. This hopefully means that the new bed won't ever need watering.

Now it was time to start filling it all back up again. We started out by sacrificing a couple of large sitka spruce firewood logs to the cause, providing the substantial, slowest-decaying core.

Step 1. Logs

Next came a layer of scorched gorse bush remains, which our neighbour had burnt off a nearby hillside the year before. Still woody matter, but much smaller pieces than the core logs.

Step 2. Brush

On top of that, we happened to have a very large pile of winter brassica ready to be cleared from the rest of the veg garden.

Spent winter brassicas

So, in it went. This will break down much more rapidly.

Step 3. Garden waste

We also chucked in some rotted manure at this point, for good measure.

Step 4. Manure

As the final, swiftest decaying layer, we spread in a load of grass cuttings.

Step 5. Grass

And then it was time to Mantis (yes, that is now a verb here) the soil back over top of all.

Step 6. Tilling and covering

The soil is, of course, still heavy clay. Very sticky when wet and easily compacted. So we added a bale of wood shavings (animal bedding type), to lighten things up a bit.

Step 7. Wood shavings to be mixed in

Soon it will be time to add squash seedlings. Hope they're going to like the new bed created especially for them!

Just add seedlings