Zucchini typically grow like crazy no matter what, and produce more than most anyone can eat. The problem I had was blossom end rot. Over the years, I have come across two different kinds of Blossom end rot. Both types have similar symptoms. As soon as the zucchini started to put on, the ends would start to turn yellow, then soft, and start to rot right on the vine. Doing some research and testing my theories, I have discovered preventative methods for both types.
The first type is caused by a calcium deficiency in the soil. Zucchini need calcium to provide the proper cell structure for the fruit to hold its shape. This type can be identified by how the zucchini grow. They will start to grow as normal but before they get to any harvest-able size the end with the blossom starts to turn yellow, soften, and start to rot.
To remedy this I bought a bag of calcium carbonate and scratched it into the surface of the soil being careful not to disturb the roots too badly. I also mixed it in a bucket of water as well, and used that to watering the plants. I continued this regiment once a week for the rest of the growing season. As a result, I was able to maintain a high level of calcium in the soil and started to have beautiful zucchini to harvest right up until the first hard frost.
The second type of blossom end rot is caused when the flower was not pollinated. Determining if this type of end rot is what you are up against all you will need to do is inspect the shape of the fruit. Typically, instead of them rotting on the end and the whole thing withering, only the ends rot, and the portion next to the vine turns in to a bulbous shape. Another sign is when only a few blossoms are affected. Sometimes the older fruit will be growing just fine or the younger fruit will be growing just fine.
The culprit here is not having a male blossom blooming at the same time. The effected blossoms may have started blooming before the male blossom was blooming or just after it had wilted away. I have also noticed that with the heavy thunder and hailstorms we have here in Colorado; they often tear up the male blossoms.
To identify what blossom is a male; you will want to look for one that does not have any fruit starting below it. It is often bigger than the female blossoms. To help insure you have a male blossom, blooming as often as possible to minimize this type of end rot, you can plant at least two separate zucchini plants. If you plant them, at least a week apart they will mature at a different rate and you increase your chances of having them bloom at different times. This will help insure you will always have a male blossom blooming for the bees to pollinate the rest.
I now make it a practice to till in some calcium carbonate into the soil where I plan to plant the zucchini, and plant at least two plants in an attempt to minimize blossom end rot.
Now, what to do with all those zucchinis?