Frost will kill your exposed vegetable plants! We learnt this the hard way even though we planted what we thought were supposed to be “frost resistant” varieties. Our lettuce seed packet simply said that they were suitable for planting “All Year Round” and the image on the packet showed tick marks next to all four seasons for both frost free as well as frost prone regions.
We tested the “leaf” lettuce by growing eight plants, transplanted from seedlings, under very simple cloches (plastic bottles with the bottoms cut off) for the first three weeks and they did very well in the 0-8 degree (celcius) early morning temperatures. Then, when the lettuces were big enough to harvest a leaf or two, we removed two of the cloches to see if they would indeed survive the cold.
They didn’t even last a full 24 hours and overnight they turned completely limp, the edges of the leaves looked as if they had been held too close to an open flame and the whole plant just seemed to shrivel up and die. They are still in the ground as I write this but I don’t think there’s much hope for them, do you?
On the other hand, the veggies planted in our new home made “Mini-Greenhouse” Growing Tunnel are doing very well indeed, almost as if it were the middle of spring already.
Building our Winter Growing Tunnel
We decided a few weeks ago that the seedlings that we were growing so prolifically on our new seedling rack were a bit of a waste if we were not going to transplant them into the garden, especially since we don’t have enough pots and 25lt barrels to accomodate all of them indoors either. I looked around on the internet at the various options for growing vegetables though the winter season and decided to try building a growing tunnel for one of our bigger (6×3 ft) Square Foot Garden raised boxes.
I managed to get hold of a few meters of UV resistant grow tunnel plastic sheeting from Obaro in Wonderboom for R46 per meter – these are 4m wide rolls, so that would be R46 for 1×4 meters. Three 2m lengths of 20x38mm planks for the base frame (one of which we cut in half for the two shorter ends), two 4m lengths of 20mm PVC piping (@ R10 each from Builders Warehouse) cut in half for the three struts and the top piece, a few cheap brass hinges and some duct tape was all that it took to make our growing tunnel. The whole tunnel cost us less than R250 and a couple of hours of work and we can now grow a full bed of veggies (18 squares) throughout the winter.
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We attached the base frame of the tunnel to the raised box with hinges to allow us to flip open the tunnel and have easy access to the front and sides of the bed. In the spring and summer months we can then just unscrew the hinges and the whole tunnel can be removed and stored until next winter. Now I just have to figure out how to make a collapsible one for easier storage 
If you do decide to follow in our footsteps with this project, make sure that you make provision for air vents to allow a bit fresh air to circulate through the tunnel during the day. We just cut flaps into the plastic sheeting on either end of the tunnel and attached a piece of shade cloth on the inside of the flaps to prevent bugs getting in. Open the flaps during the day to let the air circulate and close them again late in the afternoon to help trap the days warmth inside.
Using Cloches on your plants
Ok, so I bet that many of you were wondering what a “cloche” is. It is simply a container, usually glass or plastic, that is placed over the growing seedling or plant to create an “individual greenhouse” for each plant. We used these on our smaller bed and we found that 2lt plastic coke bottles with the bottoms cut off are ideal for seedlings and smaller plants. Simply take the lids off to allow air to get in and plop the whole thing over the plant.
I can understand how these plastic bottles would protect the plants against wind and a few bugs but I wondered just how much protection this type of solution would provide against the freezing early morning temperatures in Pretoria. After our little experiment with the lettuces as described above, I am now suitably impressed.
The only problem now is finding enough suitable (bigger) containers as the plants outgrow the relatively slim coke bottles. The 5lt fruit juice bottles that we are currently using on our strawberries might do the trick but, since I am a Coke addict (the cola variety of course), these bottles are a little more difficult to come by in large quantities.
The Importance of Mulching
Also, don’t forget to add a layer of mulch on top of the soil. We put down a 2-3cm layer of bark chips and this seems to work very well in preventing evaporation (keeping the soil moist) as well as keeping the soil a few degrees warmer than it would normally be at this time of year. Hay/straw/dried grass would also work and you could even scatter a layer on top of the plants at night to keep them warm, just remember to clear them so that they can get some sunlight during the day. Mulching will also help keep any stray weeds at bay and a “natural” mulch like this can then be dug into the soil after the growing season to happily compost itself back into the soil.
I have also seen people who have used small squares of old carpet or a thick black plastic “pond” sheeting with a slit and a small hole in the middle to place around the plant like a collar. This might not look very “natural” but I am assured that it works like a charm and it’s an ideal way to recycle any old bits of carpet or plastic sheeting that you have lying around.
Of course, we would love to hear of your experiences and any suggestions you may have for winter growing so please leave us a comment below or drop us an email.
Happy gardening
Mark
