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Zucchini fruits can fail to fully develop if the flowers were poorly pollinated. Extreme heat is one thing that can damage pollen and interfere with pollination.

Courtesy Meredith Seaver, USU Extension

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If pollen is damaged by high temperatures, the flowers may whither, dry and drop instead of setting fruit.

Courtesy Meredith Seaver, USU Extension

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Cherry tomatoes may continue to set fruit in hot weather for a little longer than other tomato varieties. High temperatures can damage tomato pollen and interfere with fruit set.

Courtesy Meredith Seaver, USU Extension

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Cabbage plants may struggle to form full-sized heads if watering is inconsistent or temperatures are too high.

Courtesy Meredith Seaver, USU Extension

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For the past two years, my garden has done very poorly. Plants have grown as big or well as in past years but have not produced much. The whole garden gets full sun. I started using 15-15-15 fertilizer three to four years ago and also built garden boxes at about the same time. When I made the boxes, I half-filled them with old cut-down fruit tree wood, then filled up with garden soil. I have noticed big clumps of mushrooms the past couple of years. Would that have a bad effect on the garden? Any suggestions on what I should check for?

A soil test might be helpful. It may tell you whether you need to back off with the phosphorus and potassium and use a fertilizer source that is nitrogen only. Ammonium sulfate (20 0 0) is one common example.

It would also be good to do some investigation with your watering. Once things have warmed and dried, do a normal watering, wait several hours and then check to see what happens with the water once it reaches that layer of wood. Also pay attention to how deep the soil is in the beds. Has it settled down into the “wood zone” and left fewer inches of soil above?

The mushrooms you’re seeing are the fruiting bodies of the fungi that are breaking down that tree wood. There is almost certainly some microbial activity that is using nitrogen to work on that wood, too. The mushrooms on their own shouldn’t be a problem; you can just pluck them off when you see them.

There are three common possibilities to investigate when a gardener notices a decline like this:

• There have been changes in the garden. A new water source/watering method, change in fertilizer, new soil amendments, new plant care practices, structures added or removed, etc.
• Increasing shade. It happens slowly, so we don’t always notice, but trees in our landscape or neighboring landscapes get larger, and shade increases over time. You say your garden boxes are in full sun, so we can take shade off the list of possibilities for you. If shade was the problem, you could relocate your raised beds to a sunnier part of the yard or have a certified arborist properly thin the problem tree canopy or have them do a selective and careful crown reduction (NOT the same as topping a tree).
• Problem plant choices. Some crops are more sensitive to certain conditions than others. Ask yourself which plants did the worst — cool season or warm season? Plants with the most afternoon sun or the least? Did the fruit-bearing vegetables like tomatoes, peppers and squash have the most trouble, or were the non-fruiting vegetables like beets, spinach and onions where your garden was the most disappointing?

Elsewhere in your email, you say your eggplants, onions and cherry tomatoes did OK, but your peppers, tomatillos and other tomatoes had almost no fruits. The cabbage plants looked great but only made tiny heads. The strangest thing for you was your squash; the fruits started out good but then withered and died instead of getting bigger. There are some clues here that we can use.

It sounds like you were getting good plant growth (normal size, color and foliage density), so it’s unlikely that low nitrogen is the problem. Vigorous green and leafy growth with little to no fruit can be a symptom of too much nitrogen, so you’ll want to keep that in mind as you troubleshoot in your garden.

We have had periods of extreme heat the past few summers. This can affect how well many of our favorite garden plants do.

The pollen in tomatoes, tomatillos, peppers and other fruiting vegetables is temperature sensitive. When temperatures rise into the 90s or higher, the pollen is damaged. Flowers will drop instead of setting fruit. Cherry tomatoes often continue to do well a little longer than other varieties during extreme heat.

For the squash problem, the issue could be blossom-end rot caused by inconsistent watering, poor pollination due to high temperatures or lower squash bee population because of pesticide use.

Cabbage heading can be affected by watering; inconsistent, too much or too little. High temperatures can also interfere with heading in cabbages.

Make sure your watering is deep and consistent but not frequent, study your soil report, don’t over fertilize and investigate how you can provide some light afternoon shade. Hopefully, you’ll have a better garden this summer.

Last chance for Master Gardener course registration

The 2025 Utah County Master Gardener Program registration closes on Monday and classes begin the very next day. Don’t miss this opportunity to expand your gardening knowledge and make a positive impact in our community!

You’ll find more information about the Master Gardener course at https://tinyurl.com/4e8ua59d.