What’s With This Heat?

I have been following the heat wave blanketing the US from temps in Philadelphia of 102°, to Newark at 108°, to Baltimore of 106°. When you know people in these areas, it becomes a little more personal. Compared to elsewhere, the weather seems less oppressive, but when you feel the effects, it does not matter where you are.

The highest recorded temperature was in Libya in 1922 of 138°; Death Valley in 1913 of 134°; 129° in Israel in 1942; and the highest average temperature is in Ethiopia at 94°. I wonder if these records will be beaten this year somewhere in the world.

A heat wave with oppressive temperatures and stifling humidity lingered in the Central part of our country, but has pushed eastward. What makes this particularly damaging is that many of the areas under its umbrella are not used to prolonged high temperatures and humidity like here in Niagara Falls. We are currently 85° today, and you can still only be outside for about 20 minutes before you are dripping with sweat. The experts are considering our area a place to go to cool off. With relative humidity of 66%, I personally don’t think so. We have not had rain for quite some time in the city and it is no fun outside.

Unavoidable scorching between two paved surfaces and no rain, weeds set in too.

Lawns are brown and perennials are drying back. And we will be back in the mid nineties by Friday. They call this 85° weather a cold front as severe storms race across the Great Lakes. But will Niagara be in its path? Heavens knows, we need the rain, but a 40% prediction?

This morning, I cut the flowers off many plants to lessen the need for the plants to maintain the foliage and blooms. I trimmed some back so as to have less foliage to support and topple if the storm hits us. Yesterday with temps of 94°, I moved all the potted plants into full shade. It was remarkable how they recovered in only one day’s time.

What is ironic, is even when soil is kept moist (recommended), when temperatures reach 86°, photosynthesis in many plants pretty much shut down and, in some, cell proteins start to be damaged. Water intake also decreases even though it is available to the plants. Plants simply are unable to take up enough water from their roots to replace the moisture lost from transpiration in leaves and flowers on hot days.

Pear Tree Stressed

When it gets really hot, plants rely on reserves of stored energy because there is little active photosynthetic activity. Pretty remarkable when you consider that they cannot get up and move to a cooler environment. But, under drought duress, they are more prone to disease, unfortunately.

This hydrangea has wilted in the sun despite having moist, cool soil. It will be perky again at sundown, when it can utilize the moisture in the soil in the cooling temperatures.

Moist soil due to heavy compost mulch and shading of the leaves.

Plants experience leaf scorch, bud drop, excessive wilting, and eventual death in prolonged periods of high heat.

Tender new growth of flowers gets burned off in this heat.

Long, intense sunlight is a real detriment to tender leaves and thin-skinned fruit.  The interior of fruit, like tomatoes and peppers, heat up on the sunny side to a larger degree than on the shady side of the fruit. The sun side of the fruit will blister, then get papery gray as the tomato ripens. But nature generally provides a good leaf cover, but as a gardener, I help it along. I let the bolting lettuce shade the tomatoes. I try to remember to keep even watering too.

Lettuce shading tomatoes.

Some of my plants were well positioned for the heat. The hydrangea above will be in a year’s time with its skirt of coreopsis and canopy of lilac, but the miniature hydrangea below weathers out the heat by being planted tightly in a bed surrounded by boxwood. Boxwood has an extensive root system and can weather dry spells quite well, so it provides shade for other plants in the garden, similar to my bolting lettuce above. The two hydrangea photos were taken at the same time of day, one looking much fresher than the other.

Some plants were planted just for their tolerance. Some droopy daisies, but generally pretty good in the front bed. Even the roses flushed despite the heat and drought.

Here is an example of two days of 94° degree weather on the miniature Balloon Flower.

Four days ago…now this…

Most of the flowers closed and dropped. Pretty amazing how fast the heat humbles the plants. And there are those that just defy all reasoning as to why they are still blooming or growing strong.


Coleus that is not heat wilted and Phlox which has less powdery mildew than last week. Definitely a head scratcher. If we could only figure out why some and not others….. both have mainly shaded locations, but do get hit by the sun. Makes me wonder why…


About Garden Walk Garden Talk

I love to photograph, paint, draw, design, garden, travel the world, and pass on a few tips and ideas that I learned through experience as a Master Gardener and architect. I am highly trained in my field and enjoy my work each and every day. I garden in Niagara Falls, NY in zone 6-B. Find me at: http://gardenwalkgardentalk.com
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21 Responses to What’s With This Heat?

  1. I’m sorry your plants and you and your neighbors are having such a hard time in this heat but I tell you it sure seems you’re on top of it. And know what to do to lessen the effects and be ready when the heat eases and the rain starts again. Down here in Alabama its about the same but its normal for this time of year. Well a bit hotter than usual I reckon but not anything to out of the norm but from what I read about you folks up north you’ve had the summer of your lives so far……Enjoy your blog immensely. Take care.

  2. Karen says:

    Donna, I wilt more than the flowers do in this heat; such a year. Your plants look so healthy even though they are sweltering, too. The last few days have been a real test of my determination to keep on gardening. Some days when the sweat is running in my eyes, I wonder, “Why?” but then we know the answer to this question, because we love it. That is very interesting information about why plants wilt even though the soil is damp. I have often watered a potted plant too much and had them die because I thought the reason they were wilted was due to needing more water. Very good information!

  3. One says:

    The weather is definitely extreme on your side. Shouldn’t you be indoors more? I wonder how those wildlife survive in this heat.

  4. Andrea says:

    Oh so you experience those extremes too even in that area! That is what we get during the dry season, but because the increase in temperature is a gradual process starting from the end of the rainy season, the plants are already acclimatized with the heat. Some already went into dormancy, some already shed their leaves. But when the dry season is extended, even some trees also die, just like our 4 fruit trees last year. At the start of our dry season, we don’t see plants still as healthy as yours, they are already adjusted to stop functioning or terminate life.

  5. Donna says:

    Donna I so worry about the garden and wildlife during this time. We need some relief…cooler temps or prolonged rain…I know the weeds and wildflowers in the meadow are doing great though…

  6. Tufagirl says:

    So sorry you are having to endure this heat as well. It just seems part of the normal routine here in Texas. You certainly have a mature and educated way of dealing with the heat.. I can not even think of any gardener other than myself that will relieve a little pressure from the plants by trimming off excess blooms and foliage. Everyone wants more all the time no matter the cost to the plant. Cheers.

  7. I too am amazed and dismayed by the heat. When I was in Portland,ME, on Friday, the temperature sign on the top of the tallest building read 102 degrees–on the coast of Maine!!! that has got to be record breaking.

  8. linniew says:

    Your plants look wonderful in spite of it all– you are a good caregiver to them Donna. A thoughtful post, shows the heat from the plants’ perspective! I hope there is relief soon.
    –I’ve come to appreciate our rainy Oregon July.

  9. Cat says:

    Sorry you and your garden are experiencing such extremes. It has been a tough summer all around. Hang in there and hopefully you’ll get some relief soon. Oregon is sounding better and better!

  10. dona says:

    I’m so sorry for your plants… 😦
    On the contrary here in Venice, where in July we should be about 85°F, today we are currently about 62°F!!!

  11. Holley says:

    It’s amazing to me when I see the weather reports how big this high pressure has become, and how much of the country is affected by this heat. Here we grow plants that will tolerate it, or they get replaced. In my garden, I am replacing more this year than I have ever before – I think mostly due to the drought. And they do appreciate shade! It would be nice to get some relief in both rain and lower temps. Sometimes I think the people are affected more than the plants! I know psychologically, it has been tougher for me than physically.

  12. Barbie says:

    Incredible temperatures and I am afraid this is the sign of the times. We too might see these high temperatures in summer. Our winter rain is not there – usually we have 82mm in July but we have only hit 16mm. It is also interesting that the soil is damp but the plant is still suffering. What about shade cloth?

  13. Shyrlene says:

    Donna – if there is any consolation, the Midwest just had a couple of days of rain (and some notable storms) – so 40% chance of rain is ‘hopeful’. I didn’t know how much I would appreciate the big trees in my yard until the last few weeks, though the Crab Apple tree is shedding leaves in distress. (We use a deep root feeder to help out the trees when it gets this dry.)

  14. Catherine says:

    We’ve been having the opposite weather here in the PNW. Way cooler and wetter than normal, but at least it’s not as stressful for the plants although I highly doubt we’ll get any tomatoes. Hope you can keep cool and the heat wave breaks soon.

  15. Goodness, what freakish – and uncomfortable and destructive – weather. I had no idea that photosynthesis shut down over a certain temperature. I hope the weather returns to normal soon, that level of humidity is no fun at all.

  16. Laurrie says:

    This was a good explanation of what really happens and how plants cope when it gets so hot. (Our part of Connecticut had an all time record at 103, hottest ever recorded here.) I did not get my containers into any shade and they really suffered. I think they cooked, actually. Despite plants’ wonderful adaptability, this time it was just too hot!

  17. Masha says:

    Interesting story. I hope your heat wave ends soon, and your wilting hydrangea will be happier… We have actually had quite a bit of cool weather this spring and summer, very unusual. Your front bed is gorgeous, I love the drifts of color and the happy lush plants.

  18. Paula Jo says:

    I’m sorry to hear your garden is suffering under the unusual high temperatures.
    This year everything seems to be way off and not just here in the US. we have relatives living in Germany and they are having July temperatures below the 60’s (reg. temp would be around the 80’s) with unusual strong storms and rain falls.
    Down here in Houston, TX we have faced the longest drought that I ever can remember off in all the over 20 years of me living here. Temperatures started to go above average already in Spring with only 2 days of rain between Jan. 25th and sometime begin of July.
    Let’s hope the weather conditions will get back to normal soon again.

  19. It’s amazing how backwards our weather seems. We should be having your heat, and instead I’m sitting here at two in the afternoon wearing a polar fleece! Not to mention, my tomatoes are still green. I’m not bitter, noooooooooo, not at all 😉 Please share some heat with those of us in chilly coastal California!

  20. AngryRedhead says:

    Your garden looks great! I also have some powdery mildew, wilting, etc. I have to keep reminding myself to not overwater, but the temptation is powerful!!

  21. I share your woes here in Kansas City. Trying to keep containers moist is our biggest burden , What scares me the most right now, if July has been so brutal what will August bring/?

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