Hot Weather Gardening

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If you are wondering if the hot weather is impacting the home landscape and gardens, the simple answer is, it sure is. With the high daytime temperatures and above normal night time temperatures, it is becoming increasing hard for plants to keep up with the natural moisture loss from foliage. Every plant in your yard loses moisture through the leaves. Remember the recent news story that tried to tie the "heat dome" that kept us hot to all the fields of corn, calling it corn sweat!

Leaves have openings to allow for the exchange gases in and out along with the water. One of the mechanisms plant leaves have is that the openings can be controlled to a point. If too much moisture is lost, the guard cells that create the opening begin to collapse, shutting off the exchange. When that happens nothing else is happening either. No energy is being created and moved downward into the plant.

Other responses to excessive high heat comes from our vegetables that produce fruits or seed pods. Tomatoes and Peppers are two good examples. Both will continue to produce flowers during hot weather, yet those flowers are aborted by the plant. Tomatoes and peppers react to the environment and know that when it is hot and dry, the production of fruits is "fruitless".  Once temperatures moderate and moisture is again plentiful, those flowers produced will once again begin to produce fruit after being pollinated. Pollination is another factor in whether or not fruit is produced. Pollen is very fragile and can easily die in a hot dry wind on its way to pollinate a female flower.

Once temperatures edge up into the mid-eighties, many vegetables will sit there not making any energy or allowing flowers to materialize into something we get to harvest.

Depending on the general care program for the home lawn, lawns will naturally go dormant until cooler weather and rainfall return. This is typically going to happen to lawns in public areas that receive no moisture other than what falls from the sky. This is also the case for home lawns that are not being watered. If an irrigation system is in place, lawns are still green and need to be mowed regularly.

Perennial flower beds are also showing the signs of heat and dry soils. Maybe there is a bit more foliage yellowing or browning than normal. Perennials that give us a summer bloom show have flowers that are not lasting very long. Even if the tops are failing, providing water to that perennial root system is beneficial.

Needle evergreens can appear normal and healthy and can turn from that nice deep green color to a much lighter green in a matter of days once the critical amount of moisture is lost. Keeping young and older evergreens watered is an investment in the future.

It is pretty easy to rush from the air conditioned car into the air conditioned house and forget about the home landscape when it is so hot. If the lawn is lost, 12-18 months later or less you can have a new lawn. Lose any mature tree, shrub or evergreen and you lose on several fronts. The value of your home goes down, the electricity bill goes up to cool your home, the shade lawn is now in the full sun and needs to be transitioned back to a full sun lawn.  Any shade garden out there in the sun will suffer too.

About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.