Squash rotting on end

Zucchini Rotting on the Vine

Archive: Problems Growing Zucchini

June 18, 2009

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

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

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

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

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

Comment Was this helpful? 1

The fruit on my zucchini squash begin to grow, but quickly turn brown and rot. Why

The rotting of the small squash fruits could be due to poor pollination or blossom-end rot.

For squash fruit to develop fully, bees and other pollinators must transport pollen from the male flowers to the female flowers. If the female flowers aren’t pollinated properly, the fruit will begin to grow and then suddenly shrivel up and die. Bees and other pollinators are less active in rainy weather. Rainy weather could be responsible for poor pollination and rotting of the small fruits. Drier weather conditions should increase pollinator activity.

Blossom-end rot is a physiological disorder that occurs on tomatoes, peppers, eggplant, and summer squash. On zucchini and other summer squash, the blossom end of the fruit begins to rot and within a short time the entire fruit has rotted. Blossom-end rot is caused by a lack of calcium in the developing fruit. In most cases, there is no need to apply calcium to the soil. Try to maintain an even moisture supply by watering once a week during dry weather. Also, do not over-fertilize plants. Uneven moisture supplies and excessive nitrogen inhibit calcium uptake.

My Zucchini Is Rotting on the Vine

Leptospira/iStock/Getty Images

Ready to pick 40 to 50 days after sown, zucchini (Cucurbita pepo) can bear heavy harvests, but poor weather and calcium deficiency sometimes cause rotting. An annual plant, zucchini grows in clumps of large, hairy leaves patterned with light greenish-gray splotches and streaks. Zucchini fruits are picked young when they’re about 6 to 8 inches long and 2 to 3 inches in diameter, depending on the variety. Larger fruits are tougher and less sweet.

Damp Beds

Zucchini fruits rot when lying on wet ground. Zucchini plants begin to produce fruit in early summer in cold climates and early winter and early summer in warm areas, when the weather is often wet and rainy conditions make the ground damp for long periods. Zucchini fruits lying directly on wet ground develop fruit rot, which starts at the fruit tips. In order to help control fruit rot, put a 2- to 3-inch-thick layer of clean, fresh straw beneath zucchini plants but not touching their stalks, and ensure new fruits are supported by the straw as they develop.

Low Bee Activity

Female zucchini fruits that aren’t pollinated rot and die. Each female zucchini flower has a small, immature zucchini fruit connecting to its stem. If a female flower doesn’t receive any pollen from a male flower, then the small fruit begins to develop but suddenly stops growing, shrivels and dies. Bees usually pollinate zucchini, but they’re less active than normal during cold, rainy weather. As temperatures rise and dry, sunny periods increase, more zucchini fruits usually develop. In warm climates, excessive heat can reduce bee activity. In order to hand-pollinate zucchinis, pinch off a male flower when it’s dusty with pollen, and rub it gently into the central structure of fully open female flowers.

Inconsistent Watering

Erratic watering causes blossom end rot in zucchini fruits. Blossom end rot begins as a small watery bruise at the tip of a zucchini fruit and often spreads and covers the whole end, causing a black or brown sunken depression that can turn moldy. The flower petals of an affected zucchini plant can remain attached, and usually the rest of the fruit is unaffected. A symptom of calcium deficiency, blossom end rot is caused by drought, fluctuating moisture levels in the soil, damaged roots and other factors that prevent zucchinis from absorbing calcium from the soil. Fresh, non-rotted manure and excessive nitrogen fertilizer applications also can cause blossom end rot. Water zucchini plants’ soil regularly so that the soil is constantly moist but never sodden. Also, spread a 2- to 3-inch-thick layer of organic mulch, such as garden compost or leaf mold, on top of the soil but not touching the plant stalks; mulch helps retain soil moisture.

Healthy Fruits

Zucchini plants growing in the most favorable conditions produce the healthiest fruits. Grow zucchinis in full-sun sites and well-drained soil rich in organic matter. If the soil drains poorly, then grow zucchinis on small hills 6 to 9 inches high. Space plants 24 inches apart, and fertilize the soil with a ready-to-use, slow-release, 14-14-14 granular product applied at a rate of 1/4 pound per 10 square feet when transplanting plants or once while seedlings grow strongly. Sprinkle the granules evenly on the soil around the plants, avoiding the plant stems, and work the granules gently into the surface of the soil, or apply the product according to its manufacturer’s instructions. Pick zucchini fruits regularly to encourage the plants to continue to flower and fruit.

Blossom end rot on tomatoes

Blossom end rot occurs when unripe fruit develops a brown rot at the base (the spot where the flower originated). It usually appears when fruit is about half grown and is more commonly seen in summer.

Blossom end rot occurs when there is a lack of available calcium to the plant. This can be due to several reasons:

  • Not enough calcium in the soil
  • Enough calcium is present but locked up due to soil pH (too acidic or alkaline)
  • Use of artificial fertilisers which provide excessive levels of other nutrients that are taken up at the expense of calcium
  • Calcium is present but it’s only very slowly available to the plant eg powdered lime or crushed eggshells
  • Fluctuation in soil moisture levels (eg drying out or being waterlogged) can restrict calcium uptake
  • Periods of excessive growth where calcium goes to the leaves first at the expense of the fruit

Calcium shortage can also cause browning or dieback on the tips of leaves and petals.

Plants Attacked
Common on tomatoes, capsicums, eggplants, zucchinis, cucumbers and more.

Organic Control Methods for Blossom End Rot
Assess the above mentioned causes for calcium deficiency and take action as required:

  • Boost the levels of readily available calcium by applying eco-flo lime, eco-flo dolomite or eco-flo gypsum to beds at the beginning of each planting. A second application halfway through the season is recommended for heavy bearing crops.
  • Test soil pH. If too acidic this can be quickly corrected by applying eco-flo lime or eco-flo dolomite. If too alkaline apply sulphur or organic matter (like coffee grounds) but they do take time to work.
  • Improve drainage in beds if water logging has been an issue.
  • Mulch beds and provide regular deep watering during hot weather so that plants don’t begin to dehydrate.
  • Only use organic fertilisers which don’t deliver nutrients in problematic forms eg as salts or at very high levels. We love digging in compost and manures at the beginning of each growing season and then topping up every fortnight with eco-seaweed and eco-aminogro.

How do I choose between lime, dolomite and gypsum?
All three products are high in calcium and are useful for preventing blossom end rot. Lime and dolomite will also change soil pH and make it more alkaline. So if your soil is too acidic use lime or dolomite. Gypsum however does not change pH. If the soil pH is perfect (or already alkaline) then use gypsum. Soil pH can change over time so it is important to test it 1-2 times a year and make any necessary adjustments.

Choosing between lime or dolomite is easy. Dolomite contains a bit less calcium than lime but has the added advantage of containing magnesium. Use dolomite to get the magnesium boost unless you have extremely acidic soil when the extra calcium in lime will help correct this faster.

Use the liquid forms of these calcium products (eco-flo lime, eco-flo dolomite or eco-flo gypsum) as the calcium is more readily available to the plants (compared to powdered forms) and you’ll get results faster.

Sqush Rotting On End: Squash Blossom End Rot Causes And Treatment

While blossom end rot is commonly thought of as a problem that affects tomatoes, it also affects squash plants. Squash blossom end rot is frustrating, but preventable. Let’s look at the some blossom end rot treatment tips.

Causes for Squash End Rot

The causes for squash end rot are simple. Squash blossom end rot happens due to a calcium deficiency. Calcium helps a plant create a stable structure. If a plant gets too little calcium while the fruit is developing, there isn’t enough to sufficiently build the cells on the fruit. In particular the bottom of the fruit, which grows the fastest, doesn’t get enough calcium.

As the fruit gets larger, the cells begin to collapse, starting with those weakest cells at that bottom. At the location of the squash blossom, rot sets in and a black indentation appears.

While the causes for squash end rot will not make the squash dangerous to

eat, the lack of calcium frequently causes the fruit to mature too early and the squash will not taste very good.

Blossom End Rot Treatment

There are a few things you can try for blossom end rot treatment. Keep in mind that all of these treatments must be done before squash blossom end rot appears. Once the fruit is affected, you cannot correct it.

Water evenly – If the plant goes through drastic changes in the amount of water it gets, it may not be able to take up the calcium it needs at the crucial time when the fruit is being formed. Water evenly, not too much or too little.

Add the right kind of fertilizer – Add a low nitrogen fertilizer to the soil before you plant. Too much nitrogen will cause an imbalance of growth between the roots and the leaves. If the leaves grow too fast, the plant does not have enough roots to take up calcium the squash fruit will need.

Add lime – The soil pH must be between 6.0 and 6.5 for optimal calcium uptake. Use lime to balance your soil’s pH if it is too low.

Add gypsum – Gypsum will help add calcium to the soil and will make that nutrient more readily available.

Remove the fruit and fix the problem – If squash blossom end rot appears, remove the affected fruit and use a calcium-rich foliar spray on the plant. This will ensure that the next round of squash the plant grows will have sufficient calcium to grow correctly.

The causes for squash end rot are very simple and blossom end rot treatment is easy enough when you know the source of the problem.

Leave a Reply

Your email address will not be published. Required fields are marked *