You’ve seen it before at this time of year. Those dry crispy leaves on your favorite plant. The drooping blooms on a Salvia leucantha. Damage from the sun and heat make gorgeous plants look so sad and sorry. In Southern California, the temperatures in July, August and September can soar past the 90’s and into 100’s where there they sit, oppressively, for weeks on end. Without the mercy of our “June Gloom” it’s not hard to see which plants can take the heat.
Regardless, of the plants in the garden, the question I get asked most often at this time of year, is “When can I water my plants in this heat?” It’s a super important question to get right, so let’s dive right in:
OPTION 1: DAYTIME WATERING
Definitely no. This is a terrible time to water when temperatures are high. Even in the 80’s you’re really not getting much bang for your watering buck anyway.
There are 2 main problems with watering during the day. First and foremost, the water will evaporate before any of it gets to it’s destination—the roots. No matter how long you stand there with a hose or run those sprays, the process of absorption simply takes time. Sometimes, people believe that in order to prevent the water from evaporating they should apply extra water. This is like trying to put 2 gallons of water in a 1 gallon jug. The water will simply run off into the street or drains because the soil can’t absorb the water fast enough.
The second reason watering during the day is a poor choice is that plants and all of their parts absorb heat all day long. The leaves get hot, as do the roots and the soil around them. As water is applied and makes contact with the hot leaves or roots, it essentially fries them causing burns which cannot be undone. Think about how you might check to see if a pan is hot enough on the stove. When you sprinkle water on it, what’s the reaction? SIZZLE! Same goes for plants.
OPTION 2: EVENING WATERING
Yes, but. There are some who say that evening watering on high heat days is preferred. I consider evening watering the second best of the three options. The reason given for evening watering is that it gives much more time for the soil to absorb the water during the cooler nights making it more effective. This is a valid. The longer the water has to be absorbed deeper and deeper into the soil for the roots to benefit from it the better.
With daytime watering almost no water is absorbed and morning watering offers less time than evening. I find in my climate in Pasadena CA, however that at this time of year, the temperatures stay very high well past sundown. Evening watering therefore, is still applying water to very hot plants in very hot soil which is not optimal for them. The other concern for watering at night, particularly if you’re using a hose or overhead sprays, is that water sits on the plants and gets trapped in leaf joints. If temperatures are cool enough you could be inviting some unwanted disease and mold to take hold.
If you do need to take care of watering in the evening, make it as late as possible once the temperatures have cooled significantly, and try to water low so as not to leave wet plants.
OPTION 3: MORNING WATERING
Morning watering—early morning watering—is really the best. Some sources will say that you should water by 10am. Not sure about your particular region, but in the middle of summer, if you’re watering at 10am you might as well be trying to water the sun.
With an automatic controller the ideal time is around 4am. The temps are cool, the plants and soil are cool, and you have several hours before the heat really kicks in, allowing the water to be absorbed into the soil. Also, if you have overhead sprays, you won’t run into trouble with water hanging around on the plants for so long that it starts causing disease.
If you’re a hand waterer, well, set that alarm. I’d say no later than around 6am. Maybe 7, latest. I’m not a morning person myself, but it’s well worth the effort to keep those plants healthy.
IMPORTANT SUMMER WATERING REMINDER
Last note about watering in the summer months. Be sure to do an evaluation of your irrigation system. Check for nicks or tears in your drip tubing. It causes lots of water to escape in one area and starve the other areas beyond the cut. Check for broken or bonky spray nozzles that aren’t doing their jobs as well as they should. An undetected problem in your irritation system will invariably lead to excess water waste (and higher bills).
With these tips you will be keeping that garden looking spectacular all summer long!
If you are unsure how well your irrigation is working and live in Pasadena or the surrounding cities, contact my office to schedule a full irrigation analysis.