Potatoes are grown from tubers known as “seed potatoes” and to avoid virus disease problems should be grown from Scottish Basic seed. To produce Scottish Basic seed potatoes growers have to inform SASA of their intention to do so as the crops must be inspected at intervals during their growth.
So why should you be chitting your potatoes?
Seed potato production is a long and costly procedure with the aim of producing a quality product at a sensible price. Chitting, or sprouting prior to planting, is not only an aid to producing early crops but is also an economical way of increasing the stock available for you to plant and maximise your crop.
Seed potatoes may be planted without chitting. Not chitting may cause some potatoes not to grow which can cause gaps to appear in the rows, others may produce as many as seven or eight shoots that become tall and spindly. Too many sprouts will cause you to have a yield of smaller tubers. Some people believe that this technique is a thing from the past that should no longer be carried out but I think it can help provide better crops by following the guide below.
Chitting of seed tubers is one of the vital factors in successful potato cropping. As potatoes are half hardy in Britain, to have good sturdy sprouts before planting will get the crop off to an excellent start. Early cultivars will mature up to two weeks earlier from properly chitted seed than from unchitted seed. Chitting potatoes gives them a good start from which you can select the strongest sprouts from.
For as long as I can remember people have disputed the benefits of chitting potatoes as to wether it is benefical or not – and much of the advice is just a an individuals personal experience. An example is that rubbing out all but two or three sprouts will benefit growth, but with no reference as to which chits should remain. To allow all the potato’s eyes to sprout and then rub some out at planting time is a sheer waste of the tuber’s reserves, reserves that could be better utilised producing improved, selected sprouts. It also creates the problem of regrowth of shoots which will be immature at harvest time producing only small, marble sized tubers. Any of these small tubers which are overlooked and left in the soil will become a nuisance, growing among other crops, in the following year. Rubbing eyes out is no good as the sprouts re-grow. You must cut the eyes out.
By chitting your potatoes you may select the eyes and encourage good sturdy sprouts before planting to produce earlier, improved crops. Look closely at the potatoes and you should see more eyes at the rose eye – often there are three or four, sometimes five, in a cluster. On some tubers, particularly the roundish shaped types, they may be placed off centre. If these are allowed to grow they will produce mainly small tubers. Using a potato peeler remove all the eyes in the rose end cluster by scooping approximately one eighth of an inch (3mm) deep, which should eliminate any regrowth. You must make sure that you remove the whole eye to stop any regrowth. Without the rose eyes the tuber’s food reserves will be directed to shoulder and side eyes. Set treated tubers with the rose eye end upwards on egg trays, thus allowing space for the sprouts to develop. They do not require high temperatures, but should be kept in full light on a North facing window and free from extreme cold or frost.
Allow seven to ten days for the wounds caused by removing the rose eyes to heal, then spray on alternate days with a weak solution of Nutrimate Liquid – two teaspoons to five litres (1 gallon). This will encourage sturdy sprouts, dark blue or green, or deep pink or red, depending upon the cultivar, by planting time.
Reject all tubers showing the slightest sign of disease. Cutting out the diseased part, such as dry rot or gangrene, is not the answer because if it is planted the diseased tubers will infect the soil and only produce further problems.
For various reasons, such as sprays used to deter early sprouting or storage at extreme low temperatures, some tubers will remain dormant producing no sprouts. Scottish Basic seed potatoes will not have had any sprout deterents applied and are always the best option for your garden. Growing in south west Scotland, I plant in the last week of March or the first week of April, weather permitting.
For First Earlies you can leave 2/3 sprouts per potato so that they produce good size tubers quickly in around 10/12 weeks depending on variety.
Second Earlies or Maincrops should have 3/4 sprouts per potato and should produce good sized tubers in 12/15 weeks where as it will take 15/24 weeks for Maincrop varieties to mature depending on variety.