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When watering my sunchokes I notice they get as cold as the water going on the plants. Why is the water cooling the plant so quickly instead of over time, and not staying at about the same temperature of the air, or the surface of the soil?

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    You measured the temperature of your plants before, during and after irrigation? What temperature range are we talking about?
    – Stephie ♦
    Jun 28, 2016 at 5:54
  • Are you measuring the temp of the actual plant or the soil? How? do you have a flir camera or something?
    – Ben Welborn
    Jun 28, 2016 at 12:26

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It is physics, not botany.

Water usually is colder then ambient (not really, it is just above the mean yearly temperature, which happens to be much cooler that one think, and it is lower than the day temperature). In general ground and water keep temperature more constant, so more you dig, less temperature changes you have. Around 10m (30ft) you have temperatures that don't change nor during day, nor during the year, so it is very like the mean temperature). Water pipe are installed on ground, so they are cooler than day.

There is also an additional reason. Vapor have much more energy than water, so, in order to evaporate, water take heat from ambient. One could try in the shower, with water temperature constant, changing the water stream size, it will change the "apparent" temperature. Firefighters use vaporizers also for this reasons.

So, if you need to water a plant, water the ground, with relatively large drops, or just a regular flow. If instead you need to control the temperature (it is done e.g. on tomatoes in greenhouses), very small drops will reduce temperature, and they will also evaporate quickly, so without increasing risk of deseases.

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  • plants are so much more adaptable...think of a rain shower...like DUH. What the heck is a vaporizer in the sense you are discussing? Why does 'vapor' have more energy than water in a liquid and how does this relate to plants? Other than too high humidity which will cause powdery mildew, I kid you not! Hope you've got MAX fans a blowing!! Talk about reducing temperatures! Critical to have this ventilation...especially with VAPOR, fog, humidity!!
    – stormy
    Jun 28, 2016 at 7:02
  • @stormy: rain has bigger drops, so they remain a lot more on the leave, and the water will partly be absorbed. Vaporizers, like the device used by modern fight fighter, which create very small drops. (en.wikipedia.org/wiki/Firefighting#Use_of_water). Small drops evaporate quickly, taking more energy. Because of quick evaporation, mildew doesn't have time to attack leaves (it needs 10 or more minutes, initially to hydrate and expands, then to enter intto leaves). Drop size really matter.
    – Giacomo Catenazzi
    Jun 28, 2016 at 8:29
  • I was wondering about how the sunchokes seems to cool off so much quicker due to the temperature of the water so quickly, not the physics behind it, but that answer works too.
    – black thumb
    Jun 28, 2016 at 17:03
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There's no mystery here - if you pour cold water over something, it gets cooler or cold, but once the water stops, the temperature stabilises over time. Same thing happens on your own skin...

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  • I don't pour water on the plant, I "flood" the bed with a drip system, and it drinks it up from the root system.
    – black thumb
    Jun 28, 2016 at 2:19
  • Okay, but the water you're using is cold, therefore there's a temporary temperature drop in the air around the plants and in the soil
    – Bamboo
    Jun 28, 2016 at 13:38

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