For the past couple weeks, my zucchini plants have been producing prolifically. Suddenly, this week there are almost none, and many of the zucchini flowers are unpollinated. That is, they closed up without producing zucchini, so I assume they are unpollinated, right? Why the sudden change?? I have been trimming back the zucchini plants because they shade the other plants. Could this have damaged them? In fact,
today I dug up one of the plants because it was shading a tomato plant and bell pepper plants, and I also needed room for the cukes and watermelon to grow, but I still have high hopes for the one zucchini plant I have left. Although there are no zucchinis growing on it right now. Most of the leaves look very healthy, but a few at the bottom have spots and yellowing. Could it be a disease?

Have you checked to make sure there are female flowers? My squash right now are producing only males.

Also, have you confirmed you have pollinators? I often have to hand pollinate the flowers when there are enough bees to do the job. Luckily, word has spread among the Apidaes and I've noticed lots of bumblebees and honeybees each morning visiting the squash, cucumber and eggplant flowers.

It is not a bit unusual for zucchini to produce some fruits then take a break for a few days or a week before putting forth again. The new female blossoms come on the growing ends of the vines, and if you prune them you will lose that productivity. Look to see if the blooms you have are male or female. Just be patient, I will bet it will give you more yet.

Matt and James,
There really aren't a lot of blossoms at all right now, but I think the ones on there are male. I have little choice but to trim back my zucchini plant. It would envelope everything if I didn't. Amazing plant. I'll see what happens in the next week, and if it doesn't start producing more, I'll try hand pollinating or something. I'm pretty sure I have enough bees though because my cucumber plant is getting pollinated like crazy, and my zooks were, too, until recently. Just another day in gardening school.
Thanks for your responses.

How do you know if they are pollinized or not?

If the plant is producing zooks, then the flowers are getting pollinized.

Zuccs, cucumbers, squash, pumpkins, watermelons, cantaloupes, all produce male and female blossoms. The females are little fruits with a blossom on the end of them. The ovary so to speak. Bees transport pollen from the male flowers to the female flowers and the fruits begin to swell and mature. If not pollinated, the ovaries (fruits) will wither and die. But pollinating dont make them produce new fruit. The fruit is already there, waiting to be pollinated when the blossom opens.
Mid season, hot weather and lack of rainfall/moisture, can cause the plants to stop producing. They will continue to put on male flowers, but are stressed too much to produce fruit.

quote:

Originally posted by Matt-choo:
Have you checked to make sure there are female flowers? My squash right now are producing only males.

Also, have you confirmed you have pollinators? I often have to hand pollinate the flowers when there are enough bees to do the job. Luckily, word has spread among the Apidaes and I've noticed lots of bumblebees and honeybees each morning visiting the squash, cucumber and eggplant flowers.

What causes a plant to produce only males and not females?

One reason is to prevent fertilizing its own flowers. The male flowers are produced earlier and lower down on the plant. By crossing with other plants, it increases the genetic diversity, which is important for adapting to different environmental conditions. Other plants, like peas, self pollinate. They usually are found in a less diverse environment that they are well adapted to. Of course, this refers to the wild ancestors to the plants.

By selective breeding, we can select for different flower traits. For example, some cucumbers are bred to have only female flowers, and a male pollinator plant must be grown alongside. Others will produce fruit without being fertilized. Seedless melon's need a male pollinator, even though they don't produce seeds themselves. It's something I'd like to study more when I have time.