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Greener Thumb
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Location: Los Angeles

When and why do pumpkin plants die?

I've been growing pumpkins and various squash for a few years now, and my experience from year to year is incredibly variable in terms of plant survival, disease, fruit set, fruit size/weight, etc. Some years I'll get 100 fruit from 25 vines, and other years I'll have to supplement from Smart & Final or Trader Joe's in order to host my annual pumpkin party.

One thing that puzzles me is when and why the vines die. Do they die after they're accomplished their life's purpose, e.g. making a fruit? Or after they've been alive for X days? Or do they die when the temps fall below X degrees? Or when the day length gets shorter than X hours? It is programmed in? Or is it just the plant not having enough X to survive?

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Super Green Thumb
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Location: Northern Utah Zone 5

Re: When and why do pumpkin plants die?

Hey, I have never gardened in Los Angeles and suppose we may have different problems? I will say for sure that pumpkins will die it the temperature hits 32 degrees. I have also seen some little underground Insects eat the roots/stems off just below the ground surface. If this is your problem, you can plant the seed and then treat the area with an insecticide. Diatomaceous Earth is good for a non chemical product. It will keep a lot of critters at bay.

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Re: When and why do pumpkin plants die?

It seems to me that almost universally, squash vines often die from fungal disease. Powdery mildew, grey mold, downy mildew, etc. Cucumber beetles also seem to cause many problems including acting as disease vectors.

If they live to bear fruits, different varieties seem to have basic given number of fruits that they typically support and grow to maturity. (Johnny's Selected Seeds and some other seed vendors have a comparison chart of the varieties they carry on their websites) Often it's 2 per vine. Some I have grown will grow two good ones to maturity, and two more small ones that may or may not finish growing -- sometimes the vines die before the remaining two are fully mature, sometimes first frost arrives, sometimes, the dying vines squeeze last of their energy into the runty fruits.

I have yet to fertilize squash plentifully, and my garden is not out under the open sky, however, so results may not be the same if you provide more nutrients and sunlight....

Super Green Thumb
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Re: When and why do pumpkin plants die?

I can tell you why they would die in my garden - SQUASH VINE BORERS!!! The bane of any non-moschata squash in my area, though I have no idea about your area, though it sounds like you don't have this problem, since you get squash on the vines.

As apple noted, fungus will kill many squash, and usually, when the squash vine borers are in the vines, it weakens the plants, and they will wilt, and develop powdery mildew. But, while this may be what finally does them in, the tunneled vines are what start the slow death.

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Super Green Thumb
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Location: TN/GA 7b

Re: When and why do pumpkin plants die?

Yeah squash family things are difficult and have a lot of diseases and pests they are susceptible to. I have pretty much given up on growing zucchini because of the vine borers. But even if you can keep the vine borers at bay, they may be swarmed with squash bugs and squash bugs also carry disease. And the powdery mildew and other diseases applestar mentioned.

I will say that last year was my first season in my new location. I tried zucchini again, in case it was different here and they still bit the dust from vine borers. But the butternut squash I grew did really well, despite an intensely hot dry summer. I still have some in the cupboard.

I've never tried growing pumpkins; they just take up too much room. Where I am now, I could conceivably grow a pumpkin plant, but I'm still not willing to devote that much of my space to it. I could grow a whole stand of corn in the space for one pumpkin plant and enjoy the corn a lot more!

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Re: When and why do pumpkin plants die?

I grew a pumpkin that was ready in July and the vine did not last long after that although it was the middle of summer. I think annuals have a programmed life cycle. In areas with frost, winter kills the vines but where I am the vines still decline and die. I do know that if the fruit are picked young, then the vines are more productive longer but if fruit are left on the vine, once they reach a certain stage of maturity the vines stop producing flowers and the vines slowly decline and die. That happens even in summer.

I think that annuals are just programmed for rapid growth especially in response to day length since the majority of annuals I know of grow best in summer. Winter planted annuals that do manage to grow like corn have delayed growth and take longer for the corn to mature. The plants end up living longer but at an immature stage.

Perennial and biennial plants usually take two or more years to flower and have a larger investment in a stronger root system and storage structures like bulbs in order to be able to survive more than a year. Annuals tend to have smaller root systems and quickly transfer energy to their seeds and blooms once they mature. Annuals have a longer bloom season than perennials because a lot of their energy is concentrated on seed production. Annuals produce more flowers to maximize seeds but will dry up once the seeds mature. Perennials on the other hand usually take longer for the seed structures to develop and in orchids at any rate, once a flower gets pollinated, the remainder of the flowers close and drop so energy can be diverted to ripenening the seed pod. That is why with perennials like lilies and irises, if you want them to bloom longer, need to have the seed pods removed. I am guessing that there must be some sort of biofeedback mechanism that guides the plants throughout their life cycle.

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