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.

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fairegarden said...

This is exactly the information I needed, Simon, thanks! We are new to potato growing and keep looking at the sprawling plants, wondering how to know when the time has come. Now we will check for flowers.

Anna said...

Much appreciate your answer. Exactly what I was searching to learn.

Anna in Maryland, having planted some Yukon peels with eyes.

Dana said...

You recommend pulling up "volunteers" the re-seeded themselves from last season, because they're not true to seed. I realize that the volunteers may not produce as much or taste the same, but is there any other reason not to eat them? Are they potentially unsafe? What about heirloom/fingerling varieties?


Hyknwolf said...

When I read this I got all excited at the thought of harvesting my first reds. But harvesting will have to remain only a thought as lifting a test plant showed no tubers...as in at all. Soil test reveals good levels, and good/proper watering has kept the soil cool enough in spite of the heat wave, and no bugs either. Plants look great above ground, so not sure why no tubers. (sigh) Will try trimming back the plants like great grandma used to do. Any other suggestions could be helpful.

Unknown said...

what if your potato plants havent produced flowers by the middle of july because mine havent and some plants are wilting even tho they are getting normal watering and fertilizer I planted on the second week of march like it states in our region

Unknown said...

well guys i found out what is going on i did a little digging with my hand into the sides of my mounds around my potatos and found 5 inch in diameter potatos ready in the second level of the mound closest to the plants im guessing they are pretty much ready i had to pull 6 potatos out of the ground since they were about 1/2 inch below the dirt so the slugs and pests didn't get to them had 2 for dinner and i tell u yukon gold are the best some one suggested to me i have potato blight from my last comment yesturday but im not having any mildew growing on the leave im guessing i have early potatos hence the the large 6 potatos i have removed already

Nathan Lanning said...

In response to the gentlemen who's plants were wilting, Mine did the same things last year despite plenty of water and treatment. I had lost hope, but when I went ahead and pulled them up in early october I was shocked to find about 6-8 potatoes per plant. my 3 plants produces a full store sized bag. I think it just depends on the type of potato you use. I actually just used Idaho potatoes from the store, wrapped them in wet paper towels and let them sprout real good before planting them in mid march.