Time to Soak: H2O in the Hot Hot Heat

So it’s a hot one this week,  Missoula. You’re thirsty, you want lemonade. You’re on day three of a +/- 90 degree stretch. You’ve been sweating, and you’re depleting what normally comprises ~ 60 percent of your body material: water. Now think about this as you slurp that lemonade: veggie plants are comprised of ~ 80 to 95 percent water, and they’ve been basking in the sun all day long.[1] As the Alabama Extension Service states, “Think of them [vegetable plants] as sacks of water with a small amount of flavoring and some vitamins,”[2] or, as Kim Gilchrist articulates, “Plants need water to help them stay upright and grow taller, to photosynthesize, and to move nutrients from their roots to their leaves and flowers.” These sacks aren’t much without water, and it’s our duty to keep them hydrated and happy.
Some arithmetic…

BethGibson_eaton_2010 (2)

Generally, our gardens need at least one inch of water per week. In hot weather, vegetables need more: add about a ½ inch per week for every 10 degrees that the average temperature is above 60 degrees.[3]

By definition, the average temperature is the daytime high plus nighttime low, divided by two. So, if the high is 95 and the low is 73, the average is 92 + 73, divided by two. The answer is 82.5. In this case, that’s about 20 degrees over 60, so you would be watering two inches total for the week (that’s the base inch plus two ½ inches). This explains why most vegetable gardeners in hot climates just laugh at the “one inch of water per week” recommendation. That simply doesn’t work in really hot weather for squash, eggplant, tomatoes, and other crops that need lots of water and have big leaves that wilt easily. This is all to say that when it’s hot, we need to be conscious about watering longer.[4]

You can measure an inch of water by keeping a rain gauge or other container under your watering system. You’ve applied an inch of water when the vessel collects water an inch deep.[5]

No need to buy a water gauge, simply use a container with a ruler.

Know the watering needs of your plants. Most plants perform best in soil that is kept moist, but not waterlogged. Some plants, however, prefer the soil to be completely dried out before being watered again. In our dry climate it’s best to err on the side of keeping the soil evenly moist, but if you really want all your plants to thrive, learn about their individual watering needs. The Royal Horticultural Society outlines some basics.

Check out Kim Gilchrist’s post, To water… or not to water, for more detailed information on watering in the heat.

Stay hydrated everyone!




[1] J.K. Kemble, Basics of Vegetable Crop Irrigation (n.p.: Alabama, A & M, and Auburn Universities, 2000), [1].

[2] Kemble, Basics of Vegetable Crop, [1]

[3] Kelly Smith, “How Much Water Do Vegetables Need?,” Bonnie Plants, accessed June 27, 2016, https://bonnieplants.com/library/how-much-water-do-vegetables-need/.

[4]  Smith, “How Much Water Do Vegetables,” Bonnie Plants.

[5] Smith, “How Much Water Do Vegetables,” Bonnie Plants.


Kemble, J.K. Basics of Vegetable Crop Irrigation. N.p.: Alabama, A & M, and Auburn      Universities; Alabama Cooperative Extension System, 2000.

Smith, Kelly. “How Much Water Do Vegetables Need?” Bonnie Plants. Accessed June 27,  2016. https://bonnieplants.com/library/how-much-water-do-vegetables-need/.