It sounds like a pollination problem. These articles will help: https://www.gardeningknowhow.com/garden-how-to/beneficial/insect-pollination-process.htm, https://www.gardeningknowhow.com/edible/vegetables/squash/squash-fruit-falling-off-the-plant.htm, https://www.gardeningknowhow.com/edible/vegetables/squash/pollinate-squash-by-hand.htm
I want to grow zucchini and squash in my garden, but I don't want it to run all over my garden and use all my space. Will these two plants grow on a trelis, if I attach them to it?
Yes, they grow well on trellises. This is called vertical gardening. This article focuses on growing vertically in containers, but you can do the same with plants in the ground. Here is more information on it: https://www.gardeningknowhow.com/edible/vegetables/vgen/growing-a-vertical-vegetable-garden.htm, https://www.gardeningknowhow.com/edible/vegetables/squash/growing-squash-on-trellises.htm Also, for the zucchini, you can look for bush varieties. These will grow in a self contained mound rather than a sprawling vine.
How can the sex of a squash be told before it bears fruit?
You normally cannot tell the difference until blooming occurs. This article will help: https://www.gardeningknowhow.com/edible/vegetables/squash/female-male-squash-blossoms.htm
I have squash and cucumbers that are only a few weeks old and I noticed that several of the stems look dry and you can actually see a slit in the stem. I pulled a few and did not see any grubs or borers in them. Any ideas would be greatly appreciated.
This article will help determine if borers are, in fact, an issue in your garden: https://www.gardeningknowhow.com/edible/vegetables/squash/squash-pests-identifying-and-preventing-squash-vine-borer.htm
I have a small watering system for planter boxes and have been told not to water the leaves of the plant because it will turn them yellow. True or not?
Watering the leaves usually does not bring about yellowing on its own; however, stressed plants are prone to developing yellow leaves. It is typically not recommended to water foliage only because this can lead to fungal infections when the plants are not or unable to dry off due to poor air circulation. Therefore, bottom watering or drip irrigation is generally preferred. This does not mean you cannot use overhead watering, however. Simply do it at a time when you can ensure that the plants will have plenty of time to 'air out' so the foliage will dry. Don't do it when it's really hot (on sunny days), as this can actually burn plants. There are a number of reasons for yellowing of squash plant leaves--this article will explain the most common causes: https://www.gardeningknowhow.com/edible/vegetables/squash/why-squash-leaves-turn-yellow.htm
After hand pollinating for squash or zucchini, is it necessary to enclose the female bloom after pollination?
No, you don't need to do this. If you have not read this yet, the following article should help: https://www.gardeningknowhow.com/edible/vegetables/squash/pollinate-squash-by-hand.htm
I am asking about cutting squash leaves. I cut all of the big leaves and left the small ones. I went back today and read that you shouldn't do this. So...do I or don't I cut the leaves? I already cut some back but don't want to destroy my plants. Thanks.
While it's okay to prune some, you should only try to remove the growing tips so as not to leave large wounds that may draw squash pests and diseases. Since you have already cut some, you may want to treat the plant with neem oil, a safe and effective pesticide and fungicide. This should help in the event that any pests or fungal issues arise. Other than that, you should just keep it watered. This article has more information about neem oil: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm If you haven't yet read it, this article will help: https://www.gardeningknowhow.com/edible/vegetables/squash/should-you-remove-squash-leaves.htm