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rainbowgardener
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potato question

So my potato plants appear thriving, almost three feet tall and bushy and spreading and very dark green at the top. My concern is that a few of the oldest leaves at the very bottom are turning bright yellow. Is that something I should worry about? A sign of nutrient deficiency? Or just that the bottom leaves are aging?
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applestar
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Re: potato question

The entire leaf? ...remember, potatoes can get all of the common diseases tomatoes are known for. One year, when I tried growing them on a raised wide row behind a deep swale, they got too much water and went down with early blight before the tomatoes which were in a bed in FRONT of the swale ever showed any significant symptoms. (In hindsight, I should have known better because potato doesn’t like too much moisture — I think they were stressed from overwatering as well.)

*a swale is constructed across a slope — in this instance I’m thinking FRONT as the higher side and BEHIND as lower, so the moisture in the bed in front drains into the swale and supplies the bed behind.
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Gary350
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Re: potato question

Yellow leaves are often a low nitrogen problem, also not enough water & hot weather can make plants leaves turn yellow & fall off. Potatoes do not need much nitrogen but they do need nitrogen an plenty of P & K & calcium. Look on the under side of the yellow leaves for tiny bugs. Your not very far south of me you have probably been getting just as much rain as us, I don't think too much rain is your problem unless raised beds are holding water like a sponge but too much water usually gives potato plants root rot.

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jal_ut
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Re: potato question

You may want to hill them up. You do this to keep the sun off the developing tubers, which are just barely under the surface of the soil. If the sun sees them, they turn green and get a bad flavor. I would not worry about those few yellow leaves.
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rainbowgardener
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Re: potato question

Yup. I planted them in a trench, so they have had soil added over the roots twice so far.
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applestar
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Re: potato question

Are they still developing yellowed leaves?

As I mentioned elsewhere, my extremely pot-bound tomatillo starts were developing bright yellow lowest leaves like you described for the potatoes. I took some of them off but left a few in place when I planted them out to see what they would do — I’m curious if those leaves will be able to recover after settling in/adverse conditions are reversed.

Since they were pot bound, lack of nutrients and water that Gary350 mentioned are definite possibilities. But it’s also possible they got waterlogged from overcompensating and/or soaking in rainwater all night.

I was thinking that since you mentioned companioning them with corn, that if the corn had reached the next phase of growth when they need extra nitrogen -and at the recommended schedule for side dressing- they might have suddenly sucked up all the available nutrients?

If the yellows leaves are not functional/lost cause, then I think you might as well remove them and hill up or mulch the stems higher like jal_ut suggested. You could just pile leaves or straw, too.
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