Growing vegetables in my location is difficult as the growing season is so short and being shortened even more with the changing climate with frosts now occurring through to the end of November which managed to destroy most of what was planted last season. The unpredictability of the current climate has led me to decide to try and create a more controlled environment to grow my vegetables in that will also extend my growing season.
After visiting friends in St. Marys and seeing the success they have had with growing vegetables in a small poly tunnel I thought it would be the ideal use for one of the existing poly tunnels on the property that I no longer using since retiring and scaling back the nursery business.
The first task was to remove the gravel and the weed mat layers beneath. I am wanting the planned vegetable beds to be in contact with the soil, not the weed matting. To do this I used my small loader to access the tunnel and remove the bulk of the material. Once that was completed I brought in the mini excavator to clean up the edges and other areas I could not access properly with the loader.
Once the gravel and old weed mat had been removed and the original topsoil exposed I laid out some new weed mat through the entire tunnel. Once that was done construction of the raised beds commenced using a heap of 200mm x 75mm hardwood sleepers I had available. The plan was to have two larger outer rows of beds with a skinnier one in the centre. Veggies to be planted in the outer rows and some espalier fruit trees to be grown in the centre. I have also placed two IBCs between the beds and have filled them with water and added a dark dye. The idea is to allow the water to heat up over time and then give back some of the heat to the tunnel overnight to help mitigate the possibility of any frost damage that might occur.
Once the beds were setup the weed mat was cut out from inside them so the beds have contact with the soil. They were filled with a soil/compost mix I had delivered from a garden supply centre and the pathways were filled with a thick layer of wood chip mulch from an old Stringbark that I had available. Couldn’t use the loader in there once the beds were installed so it was back to using a wheelbarrow and shovel for installing the soil and wood chips. The bit of exercise did me good.
We are now in the month of June and have already had a couple of sub-zero mornings with frosts. I have been researching methods to help keep the poly tunnel warmer on these cold mornings and further reduce the risk of frost damage to the vegetables. I am not looking to warm the tunnel up dramatically, only to try and prevent complete freezing occurring. One of the simple options I have found are the flower pot heaters. Most of the videos on YouTube talk about using tealight candles but I am looking for something a bit more heavy duty and longer burning. With that in mind I have put together a flowerpot heater using vegetable oil as a fuel source and carbon felt as a wick. The carbon felt is great as it does not burn away like most wicks do but it still wicks the fuel up to be burnt.
I have used a Fray Bentos Steak & Kidney pie tin as the fuel reservoir, a piece of pre-formed angle bracket that I had lying around as a wick holder and some 2.5mm carbon fibre felt for the wick. I simply cut the angle bracket into two pieces and bolted them together to make a self supporting wick stand with a large wick to provide a bigger flame. I had to play with the height of the wicking stand as I could not get it to stay alight at first. Once the height of the wick holder was reduced so the oil could easily wick up to the top it worked perfectly. Four pieces of 25mm square steel were used under the base to allow air to flow into the system. I ran an intial test on it in the workshop and it radiates some heat but not a lot. I will put another one together so I have two for the tunnel and wait for the next frost to see if they make any difference. My initial trial in the workshop ran for 7 hours on a tray of fuel so it should be good for overnight in the poly tunnel.
As they are being placed in the poly tunnel which has a woodchip base I am using a couple of paving slabs to sit them on. The beauty of using the vegetable oil is that it will not just catch fire if the wick was to fall into the oil reservoir so is a really safe way to add some heat to the poly tunnel without the worry of anything going up in flames.