The People's Potatoes Growing Course
Module 7: Harvesting Main Crop Varieties
By late July the maincrop varieties planted in April are now starting to change the colour of their leaves (haulms) from a dark green to a lighter shade. This means that the tubers are now swelling underneath and copious amounts of water should be made available to the plant. Elongated plants will be prone to falling over in high winds but eventually the whole canopy will sit down in the potato bed and this is the last stage before the leaf colour rises from light green to yellow and eventually turns to brown.
Hopefully the canopy is free from disease and you can see several strong stems per plant indicating a decent yield. You can harvest at any time but for second early and main crop varieties that will be stored, a “test dig” will need to be performed and this will indicate the size and number of tubers. Pick a plant in the row - not at the end of the row! The number of tubers seen will not change but if you leave them in the size may increase. As a general rule, 3lbs per plant is rated as good and over that is even more obtainable from modern varieties. Potatoes store very well if they are left in the ground but as the moist canopy dies back slugs become even more of a challenge and heavy rains may compromise the ridges, leaving some tubers exposed to the light. So the decision is yours to harvest now or leave them and hope they get bigger but risk crop loss.
Firstly we must ensure the skins are set so that we minimise weight loss in the store. If the skins rub off on the test dig and you want to harvest, cut the stems back to just above the soil and wait a week. This will set the skins and deter slugs.
Decide to dig up on a sunny day, starting in the morning and leave the tubers to dry thoroughly. Wet potatoes will rot in store! Once dry, place into a cloth sack and move to a dark but dry area. Exclude all light. Check the sacks in two weeks and remove any rotten tubers. The smell will give it away but hopefully this will not arise.
Potatoes will store in the UK for around three months before some varieties. You can eat tubers that have sprouts but it’s not ideal and can be avoided by choosing varieties that have a longer dormancy period. Kestrel is best used before Christmas and then I move onto Cronos.
So were you happy with your harvest? Now is the time to review and make notes for next year. The perfect season has not happened in my lifetime but part of the joy of growing is that we soon get another chance to do it all again!