Hi Nate,

There are several ways to know when potatoes are harvest-ready.

First, consider the DTM for the variety in question. For Kennebec it is 80-100 days and in our climate I consider it a late potato. Of all the varieties I grow, it normally is the last one I harvest. I've already dug up the other 8 varieties I planted, finishing them yesterday, but the bed with the Kennebecs doesn't look ready to dig yet.

Secondly, most of the time, the plants begin to yellow and die back when the tubers are as mature as they're going to get. This can happen anytime from May to July, depending on when you planted your potatoes (normally in February or March) and depending on the variety. Often, a first-time potato grower will think their plants are sick when, really, they're just dying back because they've done their job and produced the tubers.

Potatoes can be harvested at any size at which they are usable, even if the foliage isn't yellowing and dying back. It is just that leaving them growing for a longer period of time gives you more potatoes and larger potatoes. Lots of people 'rob' a few early potatoes from the plants by gently digging in the soil and finding and removing small potatoes to eat as tender new potatoes while not damaging the plant. Then they harvest the rest of the potatoes after the plant begins to die back.

Any time that you want to figure out if there are potatoes down there underneath the plant that have reached a usable size, just dig gently in the soil around the plant to check the size of the potatoes.

Those of us in southern Oklahoma have been digging potatoes for 2 or 3 weeks now. I don't know if anyone in other parts of the state is harvesting any yet. For most varieties, potatoes are a nice usable size 90-120 days after the seed potatoes were planted, although rainfall and temperatures can affect how quickly or how slowly the tubers are ready.

There are different ways to harvest. If you only grew enough for short-term eating over the next couple of months, you can cut the foliage off and dig the potatoes any time you choose. If you grew a lot and want to use some for more long-term storage, cut off the foliage and let the potatoes sit in the ground for another 3-6 days before you dig them. This allows their skin to thicken up and get tougher. The tougher skin will protect the flesh of the potatoes and allow them to last longer in storage.

Once the weather gets really hot, leaving the potatoes in the ground too long can be risky if you've had lots of rain and the soil is moist. Often. the combination of lots of moist soil and extreme heat cause the potatoes to rot. Some years I see quite a bit of rot, sometimes I see none at all, even in a wet year. Most of my rain here has fallen since mid-May and I am seeing more rot than I've ever seen before, but it is not a lot overall as a percentage of the crop.

In the fall, you often can leave potatoes in the ground and harvest them as needed as long as the soil isn't too wet. Try that in the summer, especially a wet summer, and you may find grubs and wireworms, among other pests, eating the potatoes underground.

To dig them, stick your shovel or a spading fork into the ground about a foot away from each plant, lift up and, if the foliage remains attached to the plant, pull the foliage up with one hand while lifting the soil/potatoes with the shovel or fork. It is pretty easy once you get the hang of it. After you've removed all the potatoes you have found, dig a little deeper to make sure you haven't missed any. In a normal year with average weather conditions, you'll often find 4-6 large potatoes underneath each plant and several smaller ones as well. This has been a really good year and I have found 8 large potatoes underneath some plants, with oodles of little ones. With one variety I'd only find 1-2 large potatoes, but they were gigantic. For some reason, those plants made fewer potatoes but the potatoes were really big.

Be sure to clean up all the leftover plant debris, including any partially rotted potatoes culled out of the pile of usable ones. Throw them away or compost them. Cull piles of potatoes sitting around on the ground can become a breeding ground for serious disease.

Kennebec produces heavily and often produces potatoes that are quite large.

Because it is getting so hot now, your potato plants will be happiest when mulched very well. I have mulch 12" deep on my Kennebec bed, and because the Kennebecs are in a bed raised 16" above grade level, even the exterior of the bed has grass clippings piled as thick and deep as I could get them---all in an effort to keep the soil cooler.

Potatoes start forming tubers about 3 weeks after you see plant foliage emerging from the ground. The plants set and size up the tubers best while daytime highs are in the 60s and 70s and nighttime lows are in the 40s-50s. Once your soil temperature is consistently hitting 85 degrees, the plants stop setting new tubers and the ones that you have do not enlarge a great deal more. So, once soil temperatures are really hot, there is not a lot to be gained by leaving the plants in the ground longer.

I have dug around 300 lbs. of potatoes in the last week or so, and still have the Kennebecs left to do. I suppose if I had any sense I'd be out there digging them today, but just couldn't get motivated to dig this afternoon in the heat. Don't wait too long before you check your potatoes to see if they are large enough to harvest and use. If your soil is moist, then with the kinds of temperatures we're seeing now, rot could set in pretty quickly. They're a cool-season crop, although technically, we harvest them after the cool season essentially has ended.

Dawn

We start harvesting a few new poataoes when the plants bloom and dig the entire crop when the plants have died about 3/4 of the way back, so we can still find the base of the plants. For us, planting in midMarch, potato harvest is usually close to the 4th of July. They'll have to hurry this year to be died back by then. Yours don't look like they are ready yet.

If the Mesonet three day average 2 inches vegetative covered soil temperature gets to 85 degrees i'm gonna harvest. i'd like to see a little die back. 4th of July though will be about as long as i can leave them alone. many thanks to all for all the advice.

Hi. I live in Oklahoma, and I'm a new gardener. I planted potatoes for the first time this year, and they looked great! I waited until the vines died off, like the internet said, and dug my potatoes. The potatoes were all a nice size, but half of them were ruined. Part of the potato was a tan slimy mess, and some of the smaller potatoes were nothing but this mess. The best way to describe it is that it looked like the potatoes were dissolving.

I planted Norkota potatoes on April 20, and harvested on Aug 6. Hubby thinks I waited too long to harvest; I'm worried it is because of some disease. I also planted some Purple Adirondack potatoes, and they weren't affected at all.

Did I plant at the wrong times? If it is a disease, is there anything I can do to prevent a reoccurence? I threw all the bad potatoes away and did not compost them; is it ok to compost the vines, or should I throw them away, too? I am using raised beds, and will not be planting potatoes or tomatoes in that bed for a year or two.

Thanks for any help you can give!

Cynthia,

Potatoes are cool-season crops that grow best when the daytime temps are in the 60s/70s and nighttime temps are in the 40s/50s. So, I think you know what I'm about to say next......

I am inclined to think you waited too long to harvest them in the climate we have here. The kind of dissolving, collapsing potato flesh you describe is common with potatoes exposed to soil with very high temperatures, and that is doubly true if you are having a lot of rain in combination with those temperatures. I don't know what your air and soil temperatures have been like, and this actually has been a pretty cool and mild summer compared to recent years, but in general, you need to get your potatoes harvested in June and July depending on where you live in the state. I'm so far south I'm practically in Texas and I try to get my potatoes harvested by the end of June. Otherwise, it gets too hot and they start to rot. People in northern OK likely would be okay harvesting any time in early to mid-July most years, and might even be able to harvest as late as the latter part of July if they have well-drained soil, not too much moisture and fairly moderate summer temperatures.

The OSU-recommended planting dates for Irish potatoes are February 15th through March 10, with the earlier date being for those folks in southeastern OK and the latter date for those folks in northwestern OK. All of us in between those two extremes just choose a date somewhere in between that we think will work for us. So, obviously you planted a bit late this year.

I doubt it is a disease. I just think it is a combination of high heat and a wet June and July along with potatoes that were planted too late. Your Norkotahs might be more heat-sensitive than Purple Adirondack. In years when I haven't finished the potato harvest on time (I always start on time, but plant a lot, so sometimes the last ones I get around to digging can start to rot before I get to them), I get exactly what you are describing. It isn't always uniform either, unless you're digging them way too late. Sometimes I'll dig up and find some collapsed rotting ones and keep going down the row and harvest plenty that are fine before I reach another one where the potatoes have collapsed into a slimy mess.

Try planting earlier next year and try digging earlier. I do like to wait for the foliage to die back, but if the heat arrives really early and I am worried about the potatoes rotting before they can mature, then I clip off all the foliage and throw it on the compost pile and then let the potatoes sit in the ground a few days so the skin can toughen up for storage, and then I dig them. I'd rather harvest them earlier in a hot year and get smaller potatoes than try to leave them in the ground in the heat and get bigger, rotted potatoes.

Once my soil temperatures are routinely reaching 85 degrees at the depth at which the potato tubers are located, I just go ahead and dig them, no matter what the date on the calendar says because once the ground is that hard, they won't enlarge much more anyway.....and every day I leave them in the ground after that, they are one day closer to rotting in the hot, moist soil.

Wondering what the soil temperatures are right now? Look at the soil temperature map from the OK Mesonet that I've linked below.

Dawn

Here is a link that might be useful: Current Soil Temperatures 4

Thank you, Dawn, that really helps! I',m sure this will be my favorite forum, as I am new to Oklahoma. I was living in Arizona until I married my wonderful husband in Feb 2013 and moved to his home in Caddo. Everything in Oklahoma is a new experience for me!

Cynthia

Cynthia, You're welcome. If you're in the town of Caddo, that's Bryan County, right? I'm in between Thackerville and Marietta in Love County, two counties to your west. So, you and I will be planting and harvesting at about the same time every year. Actually, since you're two counties east of me, you probably could plant some things a week earlier than I do, depending on what the soil temps and air temps are doing. but I also push the limits to plant a bit early to beat the heat, so we may be planting at the same time anyway.

Our weather here is so highly variable that I feel like every spring is a whole new experience. You never can count on the weather in any given spring being "normal" or similar to the weather the previous spring because it can be completely different. Tim and I always say "there is no normal here".

Dawn

Welcome to Oklahoma, Cynthia. Unless you're a real desert crawler I bet you'll enjoy the occasional respite from hot dry weather.

bon

Well, mine were in the ground till yesterday late afternoon. Just didn't seem to have the time to harvest, since I got back from vacation.

and then I put them in my stoneware potato pot:

Moni

Mine are still in the ground. I don't have a place to store them so I have just been digging a few when I need them. They taste good baked but it takes forever to fry them. What makes a potato good for frying. I think mine are too moist.

For frying you need a good, high-starch potato, like any of the Russett varieties,

Thanks Dawn. When I buy seed potatoes I just pick the ones that look the best. I don't put any effort into choosing varieties like I do with tomatoes.

I love Yukon Golds, and bought just one bag of them and planted them after cutting them up, and letting the cut edge dry out a bit.

Moni