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Zucchini Rotting on the Vine

Category Vegetables
Poor pollination or a lack of calcium can result in zucchini fruit rotting before it's ready to harvest. This page has advice about how to solve common problems that result in zucchini rotting on the vine.


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August 11, 20093 found this helpful


I would like to know why my zucchini plants look great with lots of flowers and fruit but when the zucchini get about 3-4 inches they start to rot or go soft? The first fruit I picked was great but since then they have not been good! Thank you.

Hardiness Zone: 6a

Luigi from Lorain, Ohio


Sounds more like blossom rot. (BER) That is a sign of lack of calcium. A few possible solutions to cure it.
  1. Egg shells, best added when you place them underneath the plant at planting time; but you could add into the soil whenever to gradually bring up traces of calcium. I grind my egg shells until a fine powder and add to the soil and water.

  2. Liming the soil with calcium carbonate (crushed limestone). Best in the winter or off season, or before planting.

  3. There are commercial sprays available (calcium nitrate & calcium chloride) that you can spray on or around the plants themselves during the growing season.

  4. Grind up a couple dozen calcium citrate dietary supplements, dissolve it in water and water your plants. This will affect all the new fruit.

By David

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August 16, 20080 found this helpful


My problem is with my zucchini, I grow it in containers on my sun deck where I have had great success with tomatoes in the past so I thought I would try some zucchini this year along with the tomatoes. To this date, they are doing great except that some of the fruit seems to be rotting on the vine. We have been having a lot of rain the past few days (approx. 4 inches). I thought about spraying with a mixture of antibacterial soap and peroxide. Any suggestions? Thanks for your sudden response.

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.

Hand Pollinating Zucchini

  1. The flowers on the zucchini plant only open in the morning. So if you want to pollinate them yourself you have to do it first thing in the morning.

  2. Pull off the male flower and pull the petals back to expose the pollen-laden stamen.

  3. 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.

  4. 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.

Good Luck!

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July 31, 20134 found this helpful

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



August 8, 20133 found this helpful
Best Answer

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.

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By 0 found this helpful
June 18, 2009

Why do my Zucchini rot after the blossom drops off? They never get to picking size?

Hardiness Zone: 7b

By mablie


June 18, 20090 found this helpful

http://www.gard … ing-zucchini.htm

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June 18, 20091 found this helpful

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. Should these stems be removed after blossom falls off? What else needs to be done?


Hardiness Zone: 9a

Carol from Stockton, CA


Problems Growing Zucchini

In Indianapolis last year vine borers killed all my squash type plants. This year I used Nematodes to prevent this again. So far I have harvested more than I did last year and I see no signs of any problems. Moles have also been digging for Japanese beetle grubs so I'm using a trap to catch the beetles. I haven't done anything to the soil about the grubs, yet. I do water every day and they seem to love me for it. (06/25/2007)

By Mark B

Problems Growing Zucchini

I have found that too much water and poor drainage due to heavy clay-like soil can be a real problem for Zucchini plants. I always have good luck growing them except for last summer when we had a torrential rainfall that ruined my Zucchini garden. After the heavy rain, the stems and blossoms were rotting before any decent fruits could be produced. Squash plants in general like fluffy, sandy, moist, but well drained soil. They should be planted in a mound or raised bed so they wont be sitting in water after a heavy rain or watering. If the soil is heavy clay, (like ours is), try soil amendments that help loosen and promote drainage. I throw a bag of sand and a big cube of peat moss over my garden every year and till it right into the soil. This fluffs up the soil and also adds volume to it so adding additional soil for a raised bed is not necessary. Surround this with a wood frame to keep the soil from washing away and you have the perfect bed for Zucchini plants.

I used to plant 2-3 Zucchini seeds into each mound and thin the seedlings to 1 plant per mound, but recently, I've found that buying a partial flat of Zucchini plants from the local garden center is well worth the extra 2 or 3 bucks. You'll have a much earlier harvest, healthier plants, and longer growing season. Sprinkle a ring of slow release vegetable food around each plant when planting. Don't water everyday unless temps get above 90F. The large funnel shaped leaves of the Zucchini plant will channel any water that hits them directly to the base of the plant, and they also shield the soil from the sun, keeping it from drying out too quickly. Do this and you'll have more Zucchini than you'll know what to do with. Good Luck.
Ed (07/29/2007)

By Ed

Problems Growing Zucchini

Thank you for the tip on cutting the end of the vine to encourage female flower production. I was getting frustrated. I also saw on another site that rotting, mushy Zucchini can be from overuse of pesticides and mosquito spraying. I'm trying organic, but it has its own quirks, too. (04/27/2008)

By Mar Lynn

Problems Growing Zucchini

Forgot to mention: The male blossoms are good eatin'. Put them to some use. Lots of recipes online. (04/27/2008)

By Mar Lynn

curling browning leaves

I have found in the past when leaves are curling and dying often stem borers are ruining the plant. Look for a sawdust like exudation at the base of the plant stems. That is an indication you are infested. (08/12/2008)

By Richard

Problems Growing Zucchini

Why does my zucchini rot?

Blossom End Rot is a disease common to Zucchini, which causes the blossom end of the fruit to rot. Per Clemson University, "The main symptom is a dark-colored dry rot of the blossom end of the fruit. Blossom-end rot is caused by a lack of calcium in the developing fruit." So either the plant is not absorbing enough calcium from the soil or the soil doesn't have enough calcium in it to start with. The solution is to get a PH soil test kit and test your soil. If it is lacking calcium, the solution would be to add calcium to your soil. Dolomite lime supplies calcium (Ca) as well as Magnesium (Mg) to your soil. It also increases the microbial activity necessary to break down nitrogen into ammonium for absorption by your plant's roots.

If the test shows the soil is okay, then you can increase nutrient uptake to the roots of the plant by mulching and adding compost or other organic matter to your soil (sheep, poultry, cattle, or pork manure has the best carbon to nitrogen ratio), and by watering well.

What causes yellowing in zucchini?

Yellowing is usually caused by a lack of nitrogen, which can be helped by adding nitrogen-rich compost, or by adding lime, or by adding manure. Many agriculture experts have advised amending soil with lime for nitrogen deficiency. There is an issue with organic fertilizers needing to be broken down by microorganisms in the soil before the plant can absorb the nutrients properly. The nitrogen gets "tied up" in this process and does not get absorbed by your plant quickly enough, so it's often recommended to use an inorganic nitrogen application along with your organic fertilizer. Again, the best solution is to do a soil test so you'll be able to eliminate what it is "not".

If the carbon to nitrogen (C:N) ratio of the organic fertilizer is less than about 20:1, "then microorganisms will obtain adequate nitrogen for their needs and will convert the excess organic nitrogen to ammonium (NH4+). This conversion is called mineralization." Ammonium is a form of nitrogen plants can absorb. Carbon acts like a furnace or energy source to speed this conversion process. Sheep, beef, swine, or poultry manure supplies the necessary ratios; speeds up the microbial process; and gets the nutrients to your plants.

A common practice in vegetable gardening is to broadcast lime and other amendments onto the garden soil and mix it well into the dirt and let it rain on it a number of times before planting your plants. In the old days, people didn't test the soil. They always just added the lime as a rule of thumb (right along with the 10-10-10) and they usually had a gorgeous garden. But you can achieve the same proper soil balance without the chemical fertilizer by using organic fertilizers, such as liquid fish fertilizer, complemented by rich compost and organic matter to speed mineralization.


By Lee H

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May 30, 20070 found this helpful
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.


A: Lynn,

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.

Ellen Brown

More Answers:

Problems Growing Zucchini

Zucchini often produces far more male flowers than female ones. The males are those on the long stems and the females are on short stems with a small bulb (the ovary) right under the flower. If you don't see many female blossoms, cut off the tip end of the vine. This reminds the plant of its main job - to make seeds to reproduce itself. (08/08/2005)

By Beth

Problems Growing Zucchini

We live in Southern NV. We've not had a garden in several years, due to health problems, but when we did, we never had any problems growing zucchini. Actually we had so much and couldn't give it away. We'd water it in the early morn and at sundown. This was only with 6 plants! Hope this helps. Maybe someone is taking your blossoms to fry & eat? I hear fried squash blossums are quite tasty. (08/10/2005)

By badwater

Problems Growing Zucchini

I have a different problem in Sterling Heights, MI (just North of Detroit). The Zucchini grow to about 3-4 inches long and about an inch thick. At that point the tips start turning yellow and then the fruit rapidly rots back all the way to the stem. It's been hot this summer so I've been watering every other day. The soil is a bed and is well drained. I only harvested about 12 fruit from 4 plants this year. (09/12/2005)

By David Osinski

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