Exhibition Potatoes and Poly Pots
4th May 2000
Some of you may already have your exhibition potatoes planted out but I prefer to leave them until around this time when the weather is more settled and the soil has really warmed up.
Of course I will have already planted a couple of rows of the early varieties for eating, indeed I shall be enjoying my first taste of the varieties Rocket and Charlotte in two weeks time when I harvest the potatoes that I shall be staging at the Chelsea Flower Show.
My potatoes for exhibition are usually second earlies and planting them now will give me plenty of show quality tubers from mid August onwards.
I have already grown two new varieties this year which were bred by John Webster, the seed potato merchant. I was given 6 tubers of Lighthouse and 6 of Edzell Castle which was exhibited by Allister Gray at the World Potato Championship at Dundee last year . Lighthouse is a long white variety with red eyes and a smooth skin. Edzell Castle is very similar to Kestrel, having been bred from the same parent line; it has a light blue to pale purple splash and is classified as round to oval whereas Kestrel is classed as long to oval. If you want to see what they look like, visit my vegetable display at Chelsea where I hope to have a dish of each variety. Both of the above varieties will be on general release through Websters potato catalogue next year.
I intend to plant my potatoes in exactly the same way as I did last year as the potatoes generally were very good, but a few did have some small brown marks and I'm convinced that these marks are a result of too much fertiliser marking the soft skin tissue. I have grown them for a number of years at my friend Jim's garden and the soil condition is superb, having had bales of straw and peat dug in every year. The soil will be well rotovated and the potato rows opened up two spades wide and a good spit deep with a minimum of 600mmm between each row.
The next step is to scatter some 4 ounces of potato fertiliser along the bottom which is then lightly forked in. Perforated black polythene is then laid along the trench and acts as a cradle for the compost that will be placed in it to grow the potatoes. The polythene is of the type that is used in commercial greenhouses to cover the capillary matting on benches; it has fine holes pierced through it and the idea is that the growing roots of the potato will work their way through these fine holes into the fertile soil below. This will enable the haulms to grow vigorously whilst the potatoes will be encased in peat and therefore not in contact with the soil which might allow blemishes to appear on them. However, the polythene I purchased was quite thin and you have to very careful that it doesn't rip apart. Another problem occurs at the end of the growing season when everything is cleared up, the polythene cannot be dragged out of the trench as the weight of the peat inside tears it into shreds. You need to empty most of the peat from inside the row in order to remove it as the last thing you want is strips of polythene tangling in your rotovator tines next Spring.
A number of you have been enquiring about growing potatoes in polypots which is also an excellent way of producing top quality tubers for exhibition. The pots I used two years ago were more than adequate for the function and measured 12" across when filled and 11" deep; each pot will take about 17 litres of compost. If you want to have a go at this system, then the mixture to fill the bags is the same that I used last year to fill the polythene lined trenches ie: 300 litre bale of peat into which I incorporated 4lbs of Vitax Q4 and 4lbs of Seagold or Calcified seaweed. For those who need smaller mixes, the ratio is 4 ounces of each of the above elements to fill up one polypot. As the plants are growing, do make sure that the haulms are supported using strong canes pushed into the soil at the back of each pot to which the haulms should be tied using a soft strong twine.
As the potatoes had some marks last year, I intend to fill one trench with peat alone and no fertiliser whatsoever in the hope of getting some really clean skins. My thinking is that as the potato is developing, it gets all of it"s nutrients from below the polythene so the maturing tuber really needs just clean uncontaminated material around it. Incidentally don't worry about the hole sizes in the polythene being too small for the roots to get through; believe me they will easily find their way down to the soil as the evidence was there when I removed the polythene from the trench with a mass of white roots on top of the soil. Indeed on a couple of occasions a few tiny potatoes must have worked themselves through the holes and developed between the polythene and the soil.