Ultralow yield potatoes

Question

TLDR; Problem: Potato plant grows but produces low to no potatoes.

I recently tried growing potatoes in my backyard. My zip code is 27587 which I believe is zone 7a. The visible (leaf/stem) portion of the plant kept growing. Per what I've heard, I tried to "hill" the plant up to about 3-4 leafs. The growing medium was about 40% worm castings and 60% hummus. The hummus was labeled organic, and my worms are fed nearly all organic food. I grew this in a felt grow bag, and it grew past the 15 inch grow bag, so I cut out the bottom of another grow bag, wrapped that 2nd grow bag around the plant and hilled it again up to about 3-4 leafs with the same growing soil. When the plant grew again and wouldn't die, I cut another bag and made extended the bag again. I don't know why they don't make expandable grow bags btw.

The potatoes were organic, but I've had similar results with seed potatoes. I waited until the plant wilted and appeared dead before dumping out the soil from the grow bag to show the usual no potatoes. It probably had the sun over it from about 10am-5 or 6pm and indirect light during other daylight hours, blockage was due to a house, garage and trees around it.

I watered it with rain water periodically, but made sure it was never sopping wet, plus the felt bag let water out from the bottom anyway. I don't think it was over-watered, but then it never told me that. Because it kept growing for about 2.5 to 3 months, I assumed it had at least the minimum amount.

I can say that the soil was more packed at the bottom. I don't know if it said, hey the dirt is too tight, let me not make any potatoes, but I don't know what the plant was thinking. I did everything I heard to do with the Potato, but it still didn't like me.

Why?

Answer 1

If you keep hilling the potato plant up indefinitely, it's going to be confused.

Hilling up is done early in the season, and then you STOP messing with the soil level.

You leave 3-4 leaves so you don't kill the plant by completely burying it - the goal is NOT to end the season with only 3-4 leaves, the 3-4 leaves are where you stop hilling until you've heaped up the soil on the row as far as is practical from what you had set aside when digging them in at planting time, no more than a foot or so, typically.

Adding additional grow bags to the top of your original grow bag is simply not advisable. Plant them at 1/3-1/2 the grow bag depth, "hill up" to the top of the grow bag, while always leaving 3-4 leaves exposed each time you hill-up, and then let them grow tops so they can make tubers...if you keep burying the tops, they can't gather solar energy to store away in tubers.

I'd agree that the ground would be a worthwhile experiment for you to try, but not doing crazy things with grow bags would improve the odds of getting potatoes from a grow bag. Choosing a variety specifically good for "Southern" growing would also help. As would planting and harvesting them on a schedule suited to the area - I see mid-February to no later than March for planting time and harvest in June-July recommended when I consult North Carolina potato growing resources. which is rather different than "outside through the summer." Here's another, which states

Potatoes planted later than March 31 will still grow, though their yields will likely be lower than earlier planted crops because they will not have as much time to form tubers before the vines start to wither in the summer heat.

Read more at: https://chatham.ces.ncsu.edu/2017/02/its-time-to-plant-potatoes/

They suggest hilling up a grow bag minimum 6-8" on a minimum 24" deep bag. So you could probably make some 24 or 30 inch bags from your multiple 15 inch bags, and then plant, fill in as the plant grows, and then step back and let it grow - and start early enough in the year for good potato-growing weather without excessive heat.

Answer 2

Based on your comments, I'm assuming that you used potatoes that were purchased at a grocery store or market. One disadvantage of doing this is that the potatoes are not certified to be disease-free, which can certainly affect growth. Two other factors that can cause a poor harvest: excess nitrogen (especially in mid- to late summer) and the fact that many "store" potatoes are treated with a sprouting inhibitor, which can affect whether they produce tubers or not.

If you have access to a backyard, I'd recommend that you plant the potatoes in the ground rather than in grow bags, if at all possible. I suspect that water intake may also be a factor in your harvest, and in-ground growth should help to at least even out watering (less dry/wet cycling during the summer). This site has lots of good information on growing potatoes, including on ways you can tell if the plants are not producing tubers.