Zucchini fruits, then withers (cross posted on Vegetable forum)

terri_portlandJuly 26, 2006

I had this happen last year too with zucchini and winter squash: the plants have good growth, good flowers, look very healthy, then when they fruit, the fruits don't grow much and then they eventually wither and die. It's a second-year organic garden with lots of good compost. They are watered regularly.

One concern I have: there are lots of walnut leaves in the compost and I used the leaves as mulch over the winter. Any cause for concern re: toxins from the walnut leaves? I have conflicting info about using them.

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That is caused by lack of pollination. Do you have both male and female flowers? Do you have lots of bees flying around? If the fruits are not pollinated they just don't grow.

    Bookmark   July 27, 2006 at 6:37AM
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Squash vine borers could be causing the problem. Check the stem near the base for sawdust-like looking material. That is the stem chewed by svbs.

Are the walnut leaves black walnut?

    Bookmark   July 27, 2006 at 8:12AM
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The zucchini are in a part of the garden that's separate from the main garden; I haven't seen many bees over there and I think the lack of pollination might be the problem. There seem to be lots of female flowers right now but no male. Suggestions? I don't see signs of the dreaded SVB

No, not black walnut, English walnut.

thank you both!

    Bookmark   July 27, 2006 at 9:55AM
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English Walnut, Juglans regina, has the same allelopathic properties as Black Walnut, Juglans nigra.

    Bookmark   July 28, 2006 at 7:02AM
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Oh, oh. My neighbors have an English walnut which sheds leaves and nuts into our yard. I looked at a few sites and all agree, English walnuts have less jugalone than Black walnuts. This site from Cornell says composting the leaves (of Black walnut) should degrade the jugalone enough for safe use in the garden. It also says squash can survive under a Black walnut. I'll be trying to seperate the walnut leaves from the other leaves from now on.

Here is a link that might be useful: cornell

    Bookmark   July 28, 2006 at 9:10AM
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I'll vote for lack of pollination too. How many plants do you have? And is has this been going on for a while, or is it just the first few fruits? It might be that the bees haven't discovered your patch yet

    Bookmark   July 28, 2006 at 10:36AM
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katj75(z8 OR)

I would be curious if you would clarify your original statment. I read it as, you had small fruit actually start to form, and THEN it would wither and die. If the fruit actaully begins forming then I would question the pollination theory. If the BLOOMS are withering, then yes pollination, but if the small beginings of actual fruit are withering, then.......not sure.

Someone correct me if I am wrong, but if fruit is forming at all then there has been pollination.

I have struggled with "similiar" issues with squash, but my plants in general were sort of going down hill year after year, got a good start then would just...wither. Finally determined we were battling wilt, not sure which type. Stopped growing squash in that location.


    Bookmark   July 28, 2006 at 4:03PM
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Yes, the fruits start to form, then wither at about 3 -4 inches. I have three plants. These are the first of the fruits. Also, some of the flowers are withering. This morning, I'm happy to report, it looks as though some are actually going to thrive and I found a definite male flower and a definite female flower. Did a little pollinating with a brush. I haven't seen a single bee over there. But the cukes are looking really good.

I believe the fruit can begin to form without pollination.

    Bookmark   July 28, 2006 at 5:27PM
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byron(4a/5b NH)

If it starts to grow and changes color, it was pollenated,
You have Blossom End Rot

If it dies w/o starting to grow/change color, it was a lack of pollenation

    Bookmark   July 28, 2006 at 7:20PM
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By "changes color" do you mean green to yellow or pale green to dark green or ??

    Bookmark   July 28, 2006 at 7:54PM
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Blosson End Rot won't show up until late in the fruits development. Plants produce fruit for one reason and that is to propagate the species, if the fruit was not pollinated (that wee bulbous growth behind the female blossom is the fruit) it will not grow. If that fruit was partially pollinated it will grow some but may not fully develop. Some fruits may start to develop but due to this lack of pollination the plant will stop its nutrient supply and that fruit will die.

    Bookmark   July 29, 2006 at 7:15AM
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Good news! I harvested a healthy zucchini this morning and there are more on the way! Seems the pollination theory was correct. Thanks to all for the ideas -- so glad I didn't pull the plants.

    Bookmark   July 30, 2006 at 4:41PM
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The pollinators have definitely found the zucchinis. I'm harvesting at least a couple a day now from three very healthy plants. Must practice patience. I will probably be begging for people to take them off my hands by next week.

    Bookmark   August 7, 2006 at 2:09AM
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pablo_nh(z4/5 NH)

Pollination. The fruits will appear to start developing, then wither. BER shows up on one end of the fruit. I'm having a little BER on zukes this year.

Good to see that it's resolved. In the future- when you have lots of female flowers- you can pluck a male flower, pull the petals off, and directly transfer pollen into female flowers by directly sticking the male flower into the female. Sort of graphic, huh? You cal pollinate several with one male flower. Since the flowers only last half a day or so anyway, you're not doing any damage.

This works for zukes, cukes, squash, pumpkins, etc.

    Bookmark   August 7, 2006 at 1:31PM
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Was reading through these postings and noticed some concerns regarding Black Walnut trees. I have a black walnut bordering our garden. Please explain if this can be harmful to my garden. The walnut shells and the leaves do land in the garden and are tilled into the soil.

Thank You !

    Bookmark   August 10, 2006 at 12:40PM
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Need some advice, first time planting zucchini. Spring: plant just two plants they now cover an area of 8ft x 8ft huge leaves and healthly looking. Have only harvested 5 fruits and had about 6 rot after getting to be 3-4 inches in length. Seems to be lots of flowers. But I do not know how to tell the difference between the female and male flowers ??? Secondly should I cut this back it is growing like crazy but for the size of the plant the fruit production seems low? Am I being impatient?
Any advice will be appreciated.

    Bookmark   July 24, 2008 at 12:47PM
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adirondackgardener(Western Maine)

Yes, what appears to be a fruit is part of the female flower. It is the flower's ovary. The male flowers on squashes are at the end of a uniformly thin stem. The female flowers are on a thickened stem resembling the fruit. Female zuchhini flowers look like a flower on the end of a mini-zuke. My Hubbard Ssquash flowers look like little Hubbards.

Get used to seeing lots of them drop off. It's what they do. I never see fruits set early in the season.


Here is a link that might be useful: UCDavis page on squashes

    Bookmark   July 24, 2008 at 9:11PM
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The female flower, the one we get the fruits from, will have a bulbous growth behind the flower. That is the ovary, and the fruit. The only reason a plant produces a fruit that we eat is because that is the repository for the seeds that are the future plants, so only a female flower will produce a fruit. If that flower does not get pollinated, or adequately pollinated, and the fruit will not have viable seed then the plant will cut off nutrients to that starting to develop fruit and it dies and falls off, that is lack of pollination.
Lack of pollination of many of our foods is becoming a greater problem as the insects that have for eons done that pollination are being killed by what we are doing to their environment.
Sorry Teri, that someone dredged this up instead of starting a new discussion as they should have.

    Bookmark   July 26, 2008 at 6:58AM
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klo1(z7 OK)

I have a large planting of basil near my zucchini that is blooming right now. It has attracted a lot of bees so I would suggest planting this next year for help with pollination.

    Bookmark   July 27, 2008 at 9:45PM
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Thanks for your previous help!
Two items:
one; I thought there was no cross pollination with zucchini plants?? I have been harvesting 4- 10 inch zuccini from the two plants I palnted which now have taken up an area 12 x 12 feet, huge. Anyway, I now have a round zucchini on one of the vines it is about the size of two soft balls together. There are no other zucchini plants in the area. Just found this strange??

2:Can you please tell me the best way to harvest basil? I have two plants each about 24-30 inches tall and full of leaves. Way more then I could ever use, so I am giving to neighbors etc.but want to harvest the best way possible. Do I just cut off the leaves, or cut a stem full of leaves? Do I harvest from the bottom of plant or just jump around??
Thank you for your help

    Bookmark   July 30, 2008 at 10:13AM
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urbanfarmertim(5b London, ON)

Wow. What a tangled thread. Anyway, I'm going to comment on walnut, zucchini and nightshades.

I have a community garden plot that is bordered by a row of mature walnut trees. I'm guessing, but I'd estimate that the trees are at least 40 years old, and probably closer to 60. My plot is approximately 20ft from the drip line of the trees. My experience is that zucchini tolerate walnut fine - normal growth and production (with pollination!)

My tomatoes and potatoes OTOH look like they've been sprayed with Round-Up. Research confirms it - walnut trees are murder on nightshades, but corn, carrots, onions, squash all tolerate them fine.



    Bookmark   July 30, 2008 at 9:06PM
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Never mind the post with the round zucchini, it is a pumpkin.I had planted a pumpkin plant at the same time I planted the zucchini but I thought it had failed. First time with both zucchini and a pumpkin, didn't know the leaves look the same. So I now have two green pumpkins and a bunch of zuccini plus two huge basil plants. Do I harvest the basil from the top bottom or just jump around the plant?

    Bookmark   August 4, 2008 at 10:13AM
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lots of great info! Looks like I might need to be a bee for a day!!! Thanks everyone!

    Bookmark   July 1, 2009 at 1:29PM
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