Polytunnel/Tunnelhouse 101

Something I get asked a lot about is our polytunnel. I am always happy to talk about it as we love it SO much so I thought it was time I answered a few common questions I get about our specific tunnel and about growing in a polytunnel in general so here it is: everything you need to know about building or buying and growing in a polytunnel or tunnel house!

Buying a polytunnel

We bought a very cheap kitset polytunnel from Trademe in 2014. You can see what it looked like originally in this post.

After a couple of seasons, the cover started to disintegrate and we got frustrated with having to roll up the door each time we went in there, so we made the decision to modify it.

Josh built a front and back out of plywood with a hinged door at the front and windows for ventilation at each end which we covered in wire mesh. We then covered the tunnel with UV resistant polythene that we purchased off Trademe.

This was a perfect work around what we had, however if we were to do it all again we would purchase a better quality polytunnel from the start. It is hard for me to recommend a brand but from reviews from friends and others I know with tunnel houses, I would go for either of these:

Morrifield Greenhouses (my neighbour has just put up one of these so I'll update when I've checked it out!)

Redpath New Zealand - these also came highly recommended when I asked around

Things to consider when choosing your polytunnel

• How much space do you have?
• Do you want to build raised beds or grow in the ground?
• Do you want shelving for starting seeds?
• What sort of ventilation does it have?
• Do you live in a high wind area?

Positioning your polytunnel

You want to choose a level piece of ground to build the polytunnel on. I would also recommend choosing a spot in full sun if possible, as this is going to help reduce mould and moss growing on the inside of the polytunnel on those dark and damp winter days.

Ease of use

The more expensive polytunnels you can purchase have sliding or hinged doors, which I can highly recommend. Ours originally had a roll up door which was very frustrating, especially if you just wanted to pop in to pick something.

We also had to roll up the windows for ventilation which was frustrating as I would often forget and the tunnel would be closed up for long periods of time. Now we have wire mesh windows on the front and back which means we don't need to worry - it is well ventilated all the time.

Ventilation

Ventilation is essental for 2 reasons:

1. To keep airflow going so that the tunnel doesn't get too damp in winter or too hot in summer
2. To assist with pollination

The tunnel houses you can buy have various options for ventilation including louvres, roof vents and doors. I would recommend something that you can leave open all the time such as a window. This way you can have the door open while you are out in the garden but you can close it up and still have airflow in and out of the tunnel.

Something to keep in mind if you choose the DIY route is ensuring the mesh is small enough that pesky bugs and insects like white butterflies can't get through. The trade off with this is that bees can't get through easily but having the door open occassionally works fine for this.

If you want to grow plants in the polytunnel that need bees to pollinate them (cucumbers, zucchini, pumpkins etc) you might want to consider having windows that can be left open for bees to get inside.

Raised beds or growing in ground?

I originally thought we would just grow in ground but Josh built raised beds for the polytunnel which I LOVE! Although it is an added expense, they are much easier to garden and being raised beds they drain better, the soil stays warmer and I think they make it look much nicer!

Irrigation

One of the most important things to consider! You can opt to just hand water but I would highly recommend looking into setting up a simple irrigation system. We are planning on re doing our irrigation this spring so I will share when we do that!

You can buy all the pipe, sprinklers and accessories you need from Mitre 10 or Bunnings and they are reasonably inexpensive.

We set up a sprinkler system which has worked really well for us. We are planning to change over to a drip line system this year though, as I have found that as some plants grow quite large, they are blocking the water from getting to some parts of the garden. Watering from the base of plants is the most recommended way to do it, so we will be trying this out.

What can you plant in the polytunnel?

Almost anything!! My favourite things to have in the polytunnel are:

All year round:

• Herbs - parsley, thyme, rosemary, oregano
• Lettuces
• Spinach
• Carrots

Spring/Summer:

• Strawberries (number 1 favourite, they do SO well in here!)
• Peppers and chillies - we get a really long season out of these as the tunnel protects them from the frost that ruins all the fruit!
• Cherry tomatoes
• Basil
• Brassicas - broccoli, cabbages (great for protecting against white butterflies)
• Carrots

Autumn/Winter:

• Silverbeet
• Coriander
• Brassicas - broccoli, cauliflower, brocoflower, cabbages
• Radishes
• Spring onions
• Beetroot

Things I haven't had any luck with in the polytunnel

• Cucumbers (due to not being able to be pollinated, although you could do this yourself using the paintbrush method)
• Zucchini (same issue as cucumbers)
• Beans
• Anything that takes up a lot of room

Things I am undecided on:

Big tomatoes - they grow for longer in the polytunnel but I have definitely always had better harvests from my outside tomato plants which again I think is due to the lack of pollination. I still put a couple of plants in the polytunnel to keep our harvest going through until about May though. Cherry tomatoes do particularly well in there though.

Things I am planning to try this year:

• Potatoes
• Blueberries
• Raspberries

Maintenance and Cleaning

To be honest, we don't do a whole lot of maintenance on our polytunnel - it doesn't really need it! The plastic covering has a few claw marks in it thanks to our excitable labrador and the base of the plastic near where the sprinklers are is a little discoloured thanks to the bore water we use to water the garden but other than that, because it is adequately ventilated all the time and is in full sun, we don't have problems with mould or mildew.

Lighting/heating

We don't have any form of lighting or heating in our polytunnel and we haven't needed it, however we live in the Waikato which only gets a few good frosts every winter so it's pretty mild. It's worth keeping in mind that if you live somewhere it snows or gets extremely heavy frosts, your plants and the ground can still freeze so you may want the option of closing up the tunnel completely to help.

If we were to use any type of heating in the polytunnel it would be heat pads for starting seeds on shelves but I still prefer to start my seeds inside in early spring.

Comment below if you have any other questions about polytunnels/tunnelhouses and I'll do my best to answer them.

Happy growing!