Poor pollination can keep your squash from producing. This guide is about zucchini rotting on vine.
Here are questions related to Zucchini Rotting on the Vine.
Why are my fruit rotting when they get about 2 inches long and yes they are rotting from the flower. I can't understand it. In the past they have been fine. Any suggestions?
By Jack K
By David M.  08/08/2013
Sounds like Blossom End rot. Your soil is lacking calcium. The easiest way is to add crushed egg shells to your soil around your plants. I actually grind my eggs shells in a coffee grinder before adding to my plants. It takes a while to work, but it works wonders.
Why do my Zucchini rot after the blossom drops off? They never get to picking size?
Hardiness Zone: 7b
By mcw  06/18/2009
Why are my zucchini turning yellow and falling off when they are about 1 inch long or less?
My zucchini has produced only one 6 in. zucchini in the last month. The plant seems to produce flowers and I have tried to pollinate them myself for lack of bees in our area. However, the fruit that comes onto the plant starts getting soft at the tip once they are about 2 in. long. I used to have good success with this plant. Please help.
Hardiness Zone: 9a
By Eddie from Redding, CA
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Q: Am I the only gardener in the US who doesn't have enough zucchini squash? I planted four zucchini plants in my raised-bed garden, thinking that they would produce plenty for my small family. The plants have grown well and are quite large, but have so far only produced about 10 squashes this whole summer (this is a total count, not 10 from each plant).
Most of the flowers seem to fall off before they get pollinated. Any suggestions? I live in Albuquerque, NM, so plants get plenty of sun, and I water them regularly.
If flowers appear but you don't get much fruit, it's probably due to a lack of pollination. This sometimes happens if bee activity is low in your area or you've had a stretch of cooler weather. My suggestion would be to consider pollinating them by hand. The first flowers to bloom are usually the males and they do not form any fruit. The female flowers are identifiable by a swelling at the base of the flower. To pollinate by hand, you can cut off the male flowers, remove the petals, and rub the stamen of the male flowers against the stigmas (the sticky part at the ends of each pistil) on the female flowers. If you prefer, simply transfer the pollen from male flower to female flower with a small artists paint brush or Q-Tip. Keep track of which stems you have pollinated by tying a twist tie of piece of string around the stem. Also, make sure to harvest the squash when they are small (about 3-4 inches across and 4-6 inches long) to increase the plant's productivity.
By David Osinski
Hardiness Zone: 6a
Ray from Pittsburgh, PA
Spraying an antibacterial soap isn't necessary until your seeing signs of disease. From what you wrote, it sounds like the leaves and vines on your zucchini are fine (no signs of disease or insect problems), and it's just the fruit rotting on the vine that is the problem. Since your getting fruits, you must be getting flowers. This tells me you're probably just having pollination problems. Is the zucchini rotting from the blossom ends? When young fruit on healthy plants begin to rot from the blossom end, they are usually not getting pollinated properly. This can be due to a lack of bees in the area, or in your case, as a result of adverse weather conditions that may be keeping the bees away.
To get a successful zucchini crop, you're going to have to pollinate the fruit yourself. Pull off the male flower and pull the petals back to expose the pollen-laden stamen. Then carefully rub the male flower on the center stigma of the female flower making sure that the pollen makes good contact. The female flowers have a distinct enlargement directly behind their petals (this is actually the immature zucchini), while the male flowers are often smaller and attached to the vine by just a long, slender stem.Another method is to use a cotton swab to transfer the pollen between flowers. This way is more efficient because you can pollinate up to three female flowers with the pollen from one male. If the rot is starting on the underside of the fruit where it's coming into contact with wet soil, raise the zucchini off the ground with a sling made from pantyhose or prop them up using a tin can or small plastic container to keep them off the soil.
I have had poor success with growing Zucchini plants that produce zucchini. There are ants in blossoms and many stems that do not produce Zucchini.