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:
- To keep airflow going so that the tunnel doesn't get too damp in winter or too hot in summer
- 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 accesories 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!
Hi Laura. we are inspired. Can i ask why you went for clear plastic sheeting and was you original setup covered in a green PE mesh cloth and if so how was that for growing?? cheers pie , brendan & lelly.
Hi Brendan. Yes the original was the green mesh looking plastic and it disintegrated after only a couple of years - we opted for the more heavy duty as we get a lot of wind and occasionally sea spray and this has proven to be very durable, we still don't need to replace it and it's been a good 5 years now since we put this on! Laura
Hi,
We got an awesome polytunnel about 7 years ago from Polythene and PVC in Gore. They also do really reasonable replacement covers. Ours has roll up sides to let the air flow with mesh covering the openings to keep bugs out, nice big doors at each end and it has held up to plenty of snow and strong wind. I've seen Morrifield ones, which don't have such good features as the Polythene & PVC ones but have a great reputation. We also had a Redpath one (50m long) for calves which was awesome but again, not as good as the Polythene & PVC.
Hi
Any new updates/reviews?
I am trying to decide between Morrifield and Redpath, which one holds up better in severe winds. Price comparison on say a 10m long tunnel house, it seems Redpath is cheaper.
Tania
Hi Tania, my neighbour (who also lives in a high wind zone) loves his Morrifield. I don't personally know anyone who has a Redpath though sorry!
Love your post. I am looking at Redpath and Morrifield and don't know which to go for. Have you got any updates? We are I a high wind area. I had green shield bugs destroy my tomatoes this year, so want to keep bugs out of a tunnel but would like bees in.
Hi Tania, my neighbour loves his Morrifield! We are in a high wind area too and it's definitely standing up!
Hi , love what you have done with your tunnel house , just added a poly tunnel to my garden in the north waikato , and was wondering what the ideal temp would have to be please ,
Great post cheers Trudy
Hi Trudy! It depends on what you are wanting to grow really! I have never actually monitored the temperature in my polytunnel. If you were to check the temperature of something, I would keep an eye on the soil temperature though as this will give you a good indication of what will grow in that temperature soil!
Hi, Laura, I love this polytunnel. It is exactly what I'm looking for. Could you please tell me how you attached the plywood to the frame. Thanks so much.
Bernie M.
Hi,
I am also considering buying a Morrifield, I want raised beds but am unsure what soil to put in?
Thanks
Denise
Hi Denise, we bought a load of topsoil to fill ours and that is what I would recommend doing.
Hey Laura, we are doing the same with ours. How did he secure the plastic at each end where the ply is?
Hi Courtney, the plastic is secured in between 2 pieces of ply, so he ran another thin piece on the front and screwed them together with the plastic in between.
Morning Laura,
Nice job on the tunnel. I have frame from the one I got from tradetested. It was a garage for my mini. The cover has become a tad sad and I want to repurpose as a tunnelhouse.
You used 2mx25m plastic to recover
How did you secure it to the frame?
Did you use all-weather tape?
Lionel
Hi Lionel, we sandwiched the plastic in between 2 pieces of plywood. If you look at the picture of the front, we have the ply wall but there is a strip around the top, this is where we have secured the plastic at the top. Along the sides, the plastic is between the wooden garden beds and the strip of ply running along the bottom of the tunnel on the outside. And we used screws to go through the lot. It's worked really well for us but if you are not using wood at all, I would definitely give all weather tape a go - no reason that shouldn't work perfectly!
I can feel your enthusiasm! I have a Merrifield poly which I love. I do have one issue though. Bees get into my tunnel through vent and the door and then they can't get out! They don't seem to head back out the door. Any ideas! The door is facing away from the evening sun so they don't seem to head in that direction.
Hi Kristina! Do you know, that is probably the only issue we have too! There is definitely not a lot of bee action that happens in our tunnel but it doesn't seem to have a negative impact on the plants which is great! Over summer I often leave the door open to let some of the heat out and then they can come in and out a bit more!
We purchased a Redpath late December. I also included the screen door as we have cats and free ranging chooks. The solar kit opens and closes the vent at certain temps. It works with wax beads inside that expand in heat and shrink in colder temps and is just ideal as I can’t reach the vent. Friend assembled it and said he admired the design but would have preferred flat ground rather than garden between retaining walls. It was easy enough to erect but do read the instructions.
Hi. I am trying to decide what tunnel house to go for. Any feedback on the Morrifield your neighbour purchased? Thanks
Hi Claire! My neighbour loves his Morrifield one! I have checked it out and it is awesome, so if we were buying one new, that's definitely what we would go for!
I have purchased a 6 meter morriefield tunnel recently its awesom well worth the investment .
2 doors a screen on one 2 ceiling vents erected by 4 of us in 4 hours.
Do you leave your strawberries with just the weedmat on them like the photo in your polytunnel, or do you put straw around them later?
Hi Marion, I just leave them like the photo but if you have problems with bugs/slugs etc adding straw around them can really help! Laura
Hi, I live in Andalucia, Spain. How would crops grow in the heat we have in the Summer? Is there a book you could recommend which explains the principles of poly tunnels. A simple one which an idiot can understand.
Hi Claire, I imagine you would need to make sure you had good ventilation to make sure it didn't get too hot in there! What temperatures do you get? Unfortunately I don't have any recommendations for books sorry! Laura
Just wanted to ask questions in regards to wind..
With what you guys did.. provided it was well secured to the ground.. would the plastic stand up to strong winds.. or would it be better to have a reinforcing protective layer??
Just wanted to know your thoughts.
Can get up to 120 km winds at times... but i do have a hip height fence around the area.. that may protect it..
I also get extremes.. down to -12 so far in winter.. up to 41 in summer..
Would i be be better to look at other options?
I have never had a poy tunnel... so i dont know..
Hi Bron! We are in a very high wind area and the plastic does hold up, however we have the plywood front facing the direction our wind comes from. I think temperature wise, as long as you could close it up in winter and make sure it could be adequately ventilated in summer you should have no problems! Laura
Thanks for the great info Laura. We had a polytunnel 14 years ago... I LOVED it. It blew away. So much for the guarantee!!
so we settled on the little greenhouse...but the plan is to put a polytunnel down the back. You've saved us a lot of leg work.
Thanks so much! Great info, really appreciate.
Aunty Wendy XX