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Kalamazoo

Hey all, second year grower but I'm a farmer and consulatant in the ag space, comfortable with agronomy and plant science.

I've got two pumpkins in an unheated greenhouse, fertility has been via compost, pelleted chicken litter, SOP, gypsum, fish/seaweed emulsion and a rotating foliar/micro program. One pumpkin has been cracking it's main vine over and over. Each time it'll be the "primary vine" and it's snapped at the furthest developed node.Then I make a secondary the new primary and few days later it cracks off. I've tried modifying water volumes, stopped all fertility a week ago, still having trouble. Vines seem too turgid like celery. I am not seeing obvious leaf indicators for defeciencies, plant is otherwise very healthy.

Second issue, pollinated the other plant 7/5 and it was slow to take off. Plants are super healthy, but the fruit has been slow to add weight. Took a week to start growing and now is about the size of a canteloupe. The plant occupies an area 20x30 and has vines over it at least 2x. Sent in a tissue sample yesterday. No obvious leaf symptoms. Seems almost like a genetic issue. Any thoughts?

7/17/2026 7:31:07 AM

Plymouth, MN

I wonder if your soil isn't running a little hot (N-heavy) and that is contributing to the brittle vines on plant A?
Plant B is only at DAP 12. At cantaloupe size it sounds like it's in within normal parameters. DAP 14 to 20 is when explosive growth will be kicking in. Hopefully you have a backup in case there is an issue, but you should be seeing a much bigger fruit in a weeks time.

7/17/2026 10:42:10 AM

Grittyville, WA

I'm curious to see the tissue results. Maybe low copper or boron. Excess potassium. Just some guesses. Nitrate is probably a factor too but I doubt it's the only factor

7/17/2026 11:24:21 AM

Kalamazoo

Thanks! Really appreciate the reassurance on the growth and thoughts on the soil.

I'm thinking I could be high N on the first one. They both were treated the same prior to planting, soil amended the same, and for the first few weeks. But as the second plant took off, I was giving it almost 2x the fish and manure tea and have not had an issue with snapping. Water is via drip on 12-18" centers with a valve to isolate each plant. I stopped the soil drench program that I was doing and slowed the foliar program to only micros, it seems to be a bit better, also cut water to 1/2. Plants are still growing like mad, but I have seen weak petioles and some blistering on the petioles on both plants.

I was seeing some initial potassium defeciencies on leaves about a month ago, so gave two shots of SOP dissolved in water at the main stem (maybe 1/2lb each time with 10 days between). Seems to cleared it up. Soil tests showed K as being a bit low, but not critical. Boron is always low here and copper can be low, but generally Mn is the problem. One of the micro foliars i use is Biomin 126, which contains chelated copper, boron and a touch of Mn. I also use a straight Mn foliar. Native soil is close to beach sand, and we put a few inches of our compost over the top before planting (goat/rabit bedding, leaves, woodchip, corn fodder from popcorn processing).

The excess K, is the concern that it would lock out Calcium?

7/17/2026 4:44:00 PM

Upa Creek, MO

I have a 2nd theory and either could be correct.

I have this exact thing happening this year to 1 of my 2 plants. The plants overlap and are in the exact same soil. One plant is healthy, has pliable vines and pumpkin on DAP 27. The other plants had 3 unprovoked main vine snaps and multiple broken secondaries. I cannot get a pumpkin to set on it either. The leaves on the problem plant are massive and healthy.

I think my issue it is a genetic thing and\or a sterile plant. I cannot explain all the vine breaks and aborts while the plant touching it has everything going perfect.

Good luck!

7/17/2026 5:36:52 PM

Grittyville, WA

There are genetic differences but I think your tissue test will show some sort of issue. I assume you are testing plant material from near the affected areas. Potassium can be foliar fed. It may interfere more with calcium if its applied to the roots. They need a lot of potassium but not so much that it interferes with calcium.

7/17/2026 6:28:05 PM

Bethlehem CT

Certain fungicides have growth hormone like effects. Like propicajazole or eagle. I think that is myclobutanil. If these get even slightly over applied they can cause curling cobra vines that split. Not sure what you are using but nitrogen isn’t always the culprit. Especially when you are using mostly organic n.

7/17/2026 10:08:31 PM

Kalamazoo

Smallmouth, I agree there may be a genetic component. The growth habit is so different between the plants, but they share some indicators that may be clues (the weak petioles on mature leaves, some bumpy or warty looking appearance on the petioles). I'm really cutting down on water now, the soil was so dry in the greenhouse early season, but easy to over water with a drip system.

I'm sure I will find something in the foliar samples, very unlikley that it's ideal across the board. I sent samples from both plants, and taken from the affected areas on the plant that is of most concern.

Big moon, thanks for the info. I'm an organic grower professionally, so I tend that direction. Was using Sonata early season, then copper soap. Had to open up the greenhouse during a power outage so gave them a shot of imidacloprid at the roots (terrible vine borers here), and at that point elected to use daconil as a fungicide. I stay organic on the garden outside, so makes spraying easy when I can keep the same program. Worked well last year outside, except for the vine borers...so that's why the pumpkins went into the greenhouse with mesh on the intakes.

On the potassium, I was seeing some calcium issues early July, so I dissolved 1lb in gypsum in hot water and gave 1/2 to each plant at the roots. I have not seen K or Ca issues since then.

7/18/2026 12:56:52 PM