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I planted red and new potatoes in early May. They were planted 6-8 inches deep. The potatoes were sprouted potatoes from our local hardware store. Our soil is heavy clay but the potatoes were planted in purchased hummus which had been worked into the soil to a depth of about 15 inches. Our climate zone is zone 9B.

No potatoes image 1

No potatoes image 2

As you can see, the potato plants only grew to about 1 ft high. Some of the plants dried up so we started harvesting today (Aug 13). To our surprise, there were no potatoes at all. We watered the potatoes using a drip system (2 GPH) that was set to 15 minutes once per week. However, the summer here has been very hot and whenever the plants looked wilted, we added an additional watering cycle.

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    Soil needs to be on the acidic side for potatoes. Did you fertilize at all? These look like plants deficient in the major chemicals with which to do photosynthesis to make the tubers. Clay is just fine IF you break it up to make raised beds. – stormy Aug 13 '17 at 20:52
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    What was grown in this soil last year? – stormy Aug 13 '17 at 20:52
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    What was the composition of your humus? – stormy Aug 13 '17 at 20:53
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    @stormy "Clay holds moisture almost too well. " - It's hard to over-water potatoes! In the main potato-growing area of the UK, the water table is only 12 inches below the surface, all the year round, whatever the amount of rainfall in any particular summer happens to be. (Much of the region is actually below sea level). – alephzero Aug 13 '17 at 22:20
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    That is one of the reasons I advocate raised beds with trenches...forget the wood and blocks, just double dug soil with 6X6" trenches at the base. I don't care what the soil is, raised beds are the way to go...potatoes are my favorite crop, it has been tough to lower the pH and I sort of over did the potatoes in my garden. Very small patches of potatoes this year. But they are so very yummy. Yellow Finn. – stormy Aug 13 '17 at 22:31
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Judging by the state of the plants when you dug them up, and what the soil surface looks like there are no nutrients whatever in it.

The potatoes tried to grow, using the material stored in the tuber, but that's as much as they managed to do. The leaves never developed properly, nor did the roots. They would have grown just as "well" if you had just put them on a concrete driveway and ignored them.

"Purchased humus" doesn't necessarily contain any nutrients. If you really want to grow potatoes in this soil, I would dig the area now to break it up, then spread about a 6 inch depth of horse manure on the surface and leave it for 3 months to let the micro-organisms to break it down and release the nutrients, then dig it in. That might give you better results next year!

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However, the summer here has been very hot

This might very well be the reason. Potatoes tend to stop the production of tubers once the soil reaches a certain temperature. Gardeners that plant their potatoes in dark plastic bags and unwittingly put the bags into a sunny spot often have the same problem.

Next year, plant your potatoes as early as possible to get a long growing phase before the summer heat sets in.

  • Raised beds solve that problem as does shade screen... – stormy Aug 13 '17 at 20:54
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    "Early May" is getting late to plant potaoes. In the UK (climate zone 8) the traditional planting date was Good Friday (mid March to mid April). That extra 4-6 weeks makes a lot of difference. Basically, you want to plant about 2 weeks before the last air frost is likely, so if you earth up the plants as soon as they show any leaves, they get the longest possible growing season without any frost damage. – alephzero Aug 13 '17 at 22:17
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    Potatoes grow their own "shade screen. " If they get away to a good start, the ground will be completely shaded by the leaves, which should be touching on adjacent rows. – alephzero Aug 13 '17 at 22:40
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In addition to the answers above (especially regarding the need to improve the soil) you should be prepared to periodically mound more soil or mulch or straw around the plants as they grow. The tubers actually grow along the stems of the plants, so if you don't cover them up, you may grow larger plants next year, but they still don't produce a crop of any size.

There are loads of resources online that outline "best practices" for growing any vegetable. Have a look and plan for next year.

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