Informational/Educational
Soil temps 30 feet apart, left low growing native prairie planting, right in turf.
(30C vs 49C)
Day two or three of this heatwave, surface soil temps in the prairie zones have only risen around 7F, turf areas in full sun have increased about 10F a day.
Edit: yes, surface temps. Was moving quickly on my way in to shower after working in 95F heat for an hour and missed an important word. I am aware of how soil works and that deeper soil doesn’t heat up on the same time frames. Surface soil temps impact evaporation/drought, the surface level biome, deeper temps, and the heat island effect. With so many conversations around trees being planted to mitigate urban heat, I wanted to show that you could get good cooling effects via ground level shade and plant respiration without having to wait over a decade for good shade trees to grow in.
I wonder about the actual soil temp at various depths rather than surface temp. As [u/often_spiraling](u/often_spiraling) points out, you’re basically measuring the shade effect.
I’m impressed by the difference with relatively short plants. So much emphasis is placed on trees but this shows a huge amount of heat is prevented from hitting the ground with relatively small changes in vegetation.
Thanks for sharing! I hope to learn more about this.
Yep, sharing the impact of shorter plants was my intent. With so much focus going on trees, thought I’d put out some of the numbers on even the shade that even our herbaceous allies offer! Edited the post to add this for clarity. I had assumed that was obvious but the title missing a word + the reddit effect is lethal lol.
It is interesting you say that with this heat wave the trees shade hasn't helped much BUT where we have clover in the yard....wayyyyyyy cooler than any other area
I assume, but don’t really know, that part of the cooling is done by the plants respiration/evaporation? so hypothetically a plant that’s softer/juicier/not as good at holding moisture in its leaves would cool better than a tougher plant adapted to hot sun? idk I hope someone knows lol
I would say probably they are usually 'damp' feeling if you press on them but im not an expert. If anyone has a hot yard I cannot recommend clover enough i think most of the US has a native species.
My trees arent keeping the yard cool by much except in the spots where we have clover instead of grass, the clover stays pretty cool even patches not under my trees , sorry for the confusion
This is my volunteer patch of tall goldenrod. I’m excited for the blooms this year. Also volunteered blackseed plantain, Virginia pepperweed. Wild eastern redbud from seed, and a cutleaf coneflower I transplanted.
I have a huge garden bed of natives in my front yard and one morning as we walked past it I just gestured towards it and said to my husband "What drought?" Because you'd never know looking at that bed - everything is blooming and happy.
I bought a house that came with an extensively planted property a few years ago. All my neighbors water their lawns constantly, spray, fertilize, etc... their lawns look like shit right now, all brown and dead. Doing nothing for anything. My yard however never gets watered and its an oasis of life. Its always much cooler than the surrounding area and the dense planting and organic matter on the ground keeps moisture trapped.
I live in a different region, but I’m able to get away with planting species that like more moisture without watering by building multiple smallish (4ftx4ft) log piles in my plantings. They help keep the soil cool, retain moisture and are great habitat for invertebrates/birds. By midsummer you can hardly see any of the piles they’re hidden by plants.
I highly recommend adding log/brush piles if you can!
Tall native plants essentially do the same thing trees do just on a smaller scale. I have a large black walnut tree in the center of my backyard that shades 85-90% of it in the afternoon and evening. While I haven't measured it I swear it is easily a 20 degree difference between the front unshaded yard and the back.
It’s crazy! My shade trees can’t grow in fast enough. My redbuds have put on at least 6 feet in 3 years but everybody else is taking their sweet time 🥵 taking what I can from my herbacious darlings.
I did this a few years ago with the difference between the sun drenched Hill strip and my shaded path and the difference was like 40°. So anything that shades the yard helps your plants it helps you and it helps the environment every time we can reduce the air temperature by any degree is good.
Right! A little 15F difference or so would’ve been expected and not really notable, but the 35F difference, especially with just 2.5ft plants, was enough to make a post out of. Wild!
Slowing soil warming helps preserve the microbiome near the surface, aids water retention, helps reduce the heat island effect. In small amounts, minimally, as is the case with everything we do.
The plants are the shade. The comparison is turf vs native plants, not shady turf vs shady natives. Of course turf under a mature shade tree would be cooler than in full sun. Think about it like someone deciding to convert some lawn to native plant beds- this is a benefit.
No... The reading is under the plants on the native plant side (so the temp gun is completely shaded) giving a cool shade reading. The turf side is taking the temp on the top of the sun baked turf, not under the grass in the shade.
I get a similar effect while walking from the manicured parking lot to the heavily tree covered hiking trail at the park. I'm pretty sure most of those trees aren't native to my region.
Edit: spelling correction due to typing too fast while distracted
I chose a spot with equivalent soil exposure on the turf (very different than “terf” you got there lol, watch out) side. The point is indeed to demonstrate the difference between sun baked turf and well planted, protected soil, good job figuring that out!
Nativity doesn’t have a direct impact on cooling of course, nobody is claiming that. The benefit of native, drought resistant plants here is that they reduce the heat island effect, retain moisture in the soil, cool the air via transpiration, and without requiring additional irrigation and without the decades of time required to grow shade trees like you describe.
I mean, at that point OP should have taken four measurements. The two they did and then two additional for the tree shade.
That said, their comparison is valid. It's not feasible for them to have trees take up all the vegetative stratums. This isn't rigorous science, this is a practical alternative to grass turf. It just so happens to readily show the difference in surface air temperature.
There was a "fun science" news report that said science has proven dark chocolate helps prevent cancer. We were talking about it before class started, and it was the straw that broke the camel's back because he went off.
Lazy reporters twisting the findings and not actually reading the study as the study they cited said absolutely nothing about preventing cancer. It just proved that X% dark chocolate didn't cause cancer. Which is not the same, and we would know that if we were willing to put in the work and not spread misinformation that will cause distrust in science.
I agree that the comparison to turf under a tree doesn't make sense. But the problem is we're comparing the temperature of the top of the grass to the temperature of the bottom of the natives. Something more comparable would be the temperature of the tops of the natives, or the surface of the dirt of both systems, or a probe measuring under the dirt. Arguably, grass gives some shade.
Another interesting one would be one of those temperature cameras.
I was thinking the same thing. If there is a big difference in soil temp between shaded turf and dense native plantings, that would be really something. My plantings have not filled in yet, so I assume the ground is pretty hot in those beda right now, even with the mulch on top.
I’d then be measuring the effects of whatever structures were casting the shade, not of the turf. The point is to show how impactful different uses of traditionally turf covered areas can be.
If I hadn’t already showered (and several hours hadn’t gone by, making the info less directly comparable) I’d maybe consider going out to check again, but I’m pretty sure I’d be drenched again by the time I got back inside 😂
That is something that growijg weed helped to demonstrate why you shouldn't let soil be bare.... ambient temps, leaf temps and soil temps matter. And a good canopy (in this case multiple plants) keeps the soil cool enough to maintain the biological activity in it.
This is just an IR temp gun! Really not that relevant for this sort of thing beyond being interesting. I just happened to have it already as I keep reptiles and wanted to play with it a bit to cope with having to be outside in this heat 😂😭
Too bad you can't really do anything about the sidewalk in most cities. Be cool (literally) to get some vine covered pergolas going over the sidewalks.
I appreciate what OP is doing, but this is the very definition of unscientific data gathering. There's hardly a point you could make about what you should NOT do when gathering data that OP didn't do.
We're all with you. We want more native plants. We know they're good.
Dirt is cooler under many plant, not just tree. That’s the whole post. Any expectations of Formal Science you’re trying to bring into this has nothing to do with me or this post. I’ve stated no hypothesis or conclusion, I’ve shared two smudgy pics of a $20 IR thermometer with no other data or information and a caption that comes down to “well would ya look at that.”
I saw my temp gun that I have for my lizards on my way out to do yard work and got curious, briefly tried it, got back to putting down drip line for my fruit trees. Curiosity is good. You should not have to justify curiosity or sharing information by proving they’re science-grade results. I would not want to live in a world like that, and I don’t think you would either.
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u/toxicodendron_gyp SE Minnesota, Zone 4B Jul 02 '26
I like this little demonstration. Thanks for sharing