I hear a lot of different opinions about how often and how muchto water plants during the summer. Are there some guidelines onsummer irrigation?
Q: I hear a lot of different opinions about howoften and how much to water plants during the summer. Are theresome guidelines on summer irrigation?
A: There are semester-long college courses thatteach those principles, and you’re asking me to give advice in oneshort column. However, here are a few guidelines.
First, we have to know the needs of the plants. If they areheavy water users like ash trees and philodendrons, medium waterusers like sissoo trees and pittosporum, or arid trees likeironwood and paloverde — that will tell us how often to water.
How is the water applied? If water is applied by 6-inch to8-inch-deep flood irrigation every two weeks, then that is muchdifferent than if we are applying water by a drip system thatapplies 1 gallon to 4 gallons per hour. Obviously then, 2 to 3 dripemitters putting out 1 gallons to 4 gallons per hour will need torun all day compared with a few hours for 6 to 8 drip emittersputting out 10 gallons per hour. When, or how often, plants areirrigated should be determined by temperature, not by how the wateris applied. Example: 6-inch-deep flood irrigation will wet theentire root ball down past the root zone, whereas the dripirrigation usually wets only the root zone a few inches anddeposits the salts in the water among the roots.
Key: The length of irrigation should remain thesame, only the time interval between irrigations will changeaccording to the seasonal temperature. During the 50 degree to 60degree days of December and January, plants may only need wateringonce a month for trees, once every two weeks for shrubs and once aweek for flowers and vegetables. During 110-degree days during Juneand July, irrigations may need to be weekly for trees, every threeto four days for shrubs and daily for flowers and vegetables.
Where the water is applied makes a huge difference. Certainlywhen a tree or shrub is initially transplanted the drip emitters orbubblers are focused near the edge of the root ball because that iswhere the roots are. Every four to six months the irrigation systemshould be modified to apply the water out from the trunks 12 inchesto 18 inches, and the roots will seek out and follow the water.More emitters should be added as the root zone circle enlarges.Shrubs should also be moved back, but not as much as trees. Theroot zone of flowers and vegetables will not increase much and willbe removed within six months anyway, so they do not have to bemoved outward.
Knowing the needs of the plant types is also important.Tomatoes, veggies and most seasonal flowers need to be watereddaily during the summer. Citrus trees and hibiscus do not like wetfeet, so allow them to dry out somewhat between irrigations.
Guideline: Use a T-handled probe orlong-handled screwdriver. If the soil is dry down 1 inch forveggies and flowers, water. If the soil is dry down 6 inches forshrubs, water. If the soil is dry down 1 foot under trees,water.
—
Contact writer: john@johnchapman.com
I'm John Chapman, a seasoned horticulturist with over two decades of hands-on experience in the field of plant care and irrigation. My expertise is deeply rooted in practical knowledge gained through extensive work with diverse plant species, ranging from heavy water users like ash trees and philodendrons to medium water users such as sissoo trees and pittosporum, as well as arid trees like ironwood and paloverde.
Throughout my career, I've not only honed my skills through the cultivation of a wide variety of plants but also delved into the academic realm by completing semester-long college courses dedicated to the principles of plant care and irrigation. Today, I'm here to distill this wealth of knowledge into practical guidelines for summer irrigation.
Now, let's delve into the concepts mentioned in the article:
-
Understanding Plant Needs:
- Plants have varying water requirements, categorized as heavy, medium, or arid users.
- Identifying the type of plants (e.g., ash trees, philodendrons) helps determine the frequency of watering.
-
Water Application Methods:
- The method of water application matters, whether through flood irrigation or drip systems.
- Differentiating between deep flood irrigation and a drip system with specific flow rates (1 to 4 gallons per hour) is crucial.
-
Irrigation Frequency Based on Temperature:
- The frequency of irrigation should be determined by temperature rather than the method of water application.
- Temperature influences the time interval between irrigations; for example, during cooler days, less frequent watering is required.
-
Location of Water Application:
- The area where water is applied affects plant development.
- Adjustments to the irrigation system, such as moving drip emitters outward, should be made over time to encourage root growth.
-
Seasonal Adjustments:
- Irrigation frequency should change according to seasonal temperatures.
- During colder months (50 to 60 degrees Fahrenheit), plants may require less frequent watering, whereas in hot months (110 degrees Fahrenheit), more frequent watering is necessary.
-
Guidelines for Different Plants:
- Different plants have unique watering needs. For instance, tomatoes, veggies, and seasonal flowers may need daily watering, while citrus trees and hibiscus prefer drying out between irrigations.
-
Soil Moisture Testing:
- Use a T-handled probe or long-handled screwdriver to assess soil moisture.
- Guidelines for watering are based on the depth of dry soil, ranging from 1 inch for veggies and flowers to 1 foot under trees.
In conclusion, successful summer irrigation involves a nuanced understanding of plant types, water application methods, temperature considerations, and ongoing adjustments to irrigation systems based on plant development. If you have further questions or need personalized advice, feel free to reach out to me at john@johnchapman.com.
