For many years now I have grown Early potatoes in containers. The current containers are 35-litre black plastic pots. It's hard to say exactly what size container is ideal for potatoes, so this year I have been trying an experiment to judge the relative performance of containers planted-up with one seed tuber and with two seed tubers. Some people assured me that one tuber would be best, since the plant would have lots of room to spread out. Others said it is better to put two tubers in each pot, because they will vie with one another to be the biggest, thus boosting overall yield. What do you think the result was? Read on...
To get a fair comparison, I planted two pots of each of my varieties of Early potato, one with a single tuber in it, and one with two. The pots were filled with exactly similar compost and fertiliser, and placed right next to each other. I have watered them with exactly the same frequency and I will be harvesting both pots on the same day. Should be a fair test then.
These are the two pots of "Annabelle". As you can see, the foliage had collapsed and was beginning to turn yellow, indications that the crop was ready for lifting.
So, the moment of truth! I just tip the pot over, spilling its contents onto a groundsheet.
This is the pot that had just one plant in it.
This is the pot that had two plants in it.
It's always an anxious moment when you do this. Will there be lots of lovely potatoes, or just a few? Will their skins be smooth, or covered in Scab? Well, these ones looked pretty good.
I placed the tubers from each pot into separate containers, impatient to see how many there were in each.
This is the yield from the pot that had just the one seed-tuber:
And this is the yield from the pot that had two seed-tubers:
And here they are side-by-side:
You'll notice that there are potatoes of many different sizes there. For a fair comparison, I discarded from both lots any tubers that were too small to be worth eating. There were probably about 10 or 12 of these in each pot. There are also several potatoes that are on the large size for First Earlies, which tells me that I could really have lifted these a week or ten days earlier. When I have grown "Annabelle" previously they have been more even-sized.
OK, so now for the results. Having taken the potatoes indoors and washed them, I weighed both batches. The 1-tuber pot yielded 628g and the 2-tuber pot yielded 1237g. So the two-tuber pot produced slightly under twice the yield of the one-tuber pot.
So what does this tell me? I think it demonstrates that a 35-litre pot can easily accommodate two seed-tubers with no effect on yield. Next year I shall revert to putting two seed-tubers in each pot! It means I can get twice the yield from exactly the same space that I would use if each pot only contained one plant.
Of course this is only the first of my four container-grown potato varieties to be harvested. The other 3 may produce different results. And just for the record, my view is that although First Earlies are typically harvested small, the yield from these "Annabelles" was on the small side. This may possibly be a result of the strange roller-coaster weather conditions we have experienced this year. On the Plus side though, the potatoes are nice and clean, with very little Scab. I attribute this to the high organic matter content of the growing-medium, which was about 50% home-made compost and 50% garden soil from a dismantled raised bed.
