Does late-season heat affect plants?

SALT LAKE CITY — Although it’s officially fall, the weather in Utah doesn’t feel like fall just yet. With the temperatures still being high for the next couple of days, here is how the late-season heat may or may not affect your plants.

How does late-season heat affect the average homeowner with a garden?

Warm-season vegetables, such as tomatoes, keep producing longer in this weather. They prefer temperatures in the 80s during the day. This means we get more fresh produce, which is not bad.

What should you be harvesting right now?

I would harvest anything I could on warm-season crops, such as peppers, tomatoes, squash, corn, etc. With the unseasonably warm weather, temperatures may suddenly drop in the next couple of weeks leading to it being too cold for growing crops. If we get a sudden killing frost, it will ruin most any usable produce.

What should you wait to harvest?

Cool-season vegetables, such as radishes, lettuce, and English field peas, tolerate temperatures around freezing. Crops such as carrots can be covered with 6 inches of straw and harvested throughout the winter.

Does waiting to harvest affect the taste of produce at all?

It depends. Temperatures that are too cool negatively affect the flavors of warm-season crops, which may not kill the plants outright but give the fruit from the plants (fruit is anything that contains a seed) an off flavor. Conversely, temperatures above 85 degrees Fahrenheit are not great for cool-season crops. These temperatures make crops such as radishes and lettuce have a bitter, unpalatable taste.

There is an incorrect theory that frost boosts the sugar levels in fall-harvested fruits, such as grapes and apples. These and others should be harvested when they are ripe. The best way to tell if they are ripe is to taste them. Waiting for frost often diminishes fruit quality because the fruit was picked too late. No professional farmers wait for frost to harvest fruit.

Does heat so late in the season affect the taste or nutrients in the harvest?

No, it does not. For the most part, taste and nutrient levels are negatively affected after the fruit is harvested and stored incorrectly. Pre-harvest, temperatures consistently above 100 degrees Fahrenheit, and incorrect irrigation affect the flavor. The temperatures we are experiencing now are not hot enough to impact flavor or nutrition.

What are some best practices or tasks before winter to keep a garden healthy at this time of year?

Remove the weeds and incorporate 1 to 3 inches of compost into the soil this fall. Fall applications of compost are better than spring applications. I would make and record a garden plan on paper or digitally for next year while keeping how things went in the garden at the top of my mind. If we wait, we will forget essential details by spring. What vegetable varieties did well, and which ones did not? Did I grow too much or not enough? While planning, it is important to remember to rotate where things are planted. Additionally, there is nothing wrong with getting garden beds and rows ready this fall for spring planting.

Should major farmers be warned? Is there anything they should be cautious of with the heat?

No, they know what they are doing if they have a large farm and have been around for years. Commercial vegetable farms must continuously monitor weather conditions to be successful. I am more worried about newer hobby gardeners. The warmer weather this fall has been a bonus for farmers. It has given them better weather to harvest and an extended growing season.

There is an increase in danger for tree fruit farmers. If we drop from the 60s and 70s to the 20s over just a few days, this isn’t good for fruit trees or any trees. Trees take weeks to achieve complete dormancy. Temperatures primarily drive the process, and a gradual temperature decrease over weeks is ideal. As trees become more dormant, sap is absent in the conductive tissue and replaced by compounds that act as natural antifreeze agents. If temperatures suddenly drop too much, the sap (which is mostly water) often gets trapped in the conductive tissue just under the bark and then freezes in the conductive tissue. Ice expands as it freezes and damages or kills the cells of the conductive tissue.

Related:

• Got green tomatoes? Here’s how you can ripen them
• Getting your garden ready for next spring
• A horticulturist’s guide to storing your fruits and vegetablesTaun Beddes is the co-host on the KSL Greenhouse show.

KSL Greenhouse is on every Saturday from 8 a.m. to 11 a.m. Follow the show on Facebook, Instagram, YouTube, and on our website.