So, how can you tell when potatoes are ready to harvest? A tricky question when your crop is obscured by a foot or two of your best soil. Without the benefit of ground penetrating radar, the most obvious method appears to be digging up the crop and having a look! Unfortunately, this action can cause unnecessary damage to the potato tubers, and - if they are not yet of a suitable size - lifting them is only going to damage the existing root structure severely delaying any future growth.
Of course there is a far easier and much less damaging way to tell when your potatoes are ready for harvesting, and it is just a matter of waiting for mother nature to show her hand.
Within a few weeks of planting your seed potatoes, fine root hairs will be produced. As these grow larger, nodules form along the roots which - in turn - will form tiny juvenile potato tubers.
These juvenile tubers will continue to swell and grow right up until the time the potato plant proper begins to produce its flowers.
As soon as this occurs, the energy from the plant will be diverted away from the production of tubers and over to the production of flowers, and the subsequent formation of its fruit and seeds.
You can consider removing any flowering heads as they form to encourage further tuber development, but with a large crop of potatoes this may be an unrealistic challenge.
So the answer to the question of when can you start lifting you potatoes is this:
As soon as they come into flower, because it is unlikely that your plants will produce and more - or any bigger - potatoes after this point.
Note. If you allow potato seeds heads to form and mature, next year you will be inundated with potato seedlings. Don't forget that these seedlings will NOT grow true to the parent plants and should be removed when seen.
HOW CAN YOU TELL WHEN TO HARVEST POTATOES?
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ORGANIC AND CULTURAL CONTROL OF POTATO BLIGHT
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WHEN ARE POTATOES READY TO HARVEST
WHY AND HOW TO CHIT POTATOES