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Wednesday, August 14, 2013

Is My Photinia Over or Under Watered?

Q. I have no idea if I am over watering or under watering. My red tip photina plants are all brown and dropping leaves left and right. My sago is turning yellow. I have a drip system and it is set for twice a day ever other day for 10 minutes. Is that enough?

Photinia growing in rock mulch

A. Usually drip irrigation is measured in gallons per hour, not in the number of minutes it was operating. Each emitter operates in a specific number of gallons, or fraction of a gallon or liters, it will deliver in one hour. 

Problem photinia
Drip irrigation does not need to come on twice a day unless the drip emitters are those emitters I don’t like very much, the kind you can twist open and get some unknown volume of water. Under the right conditions those will put out so much water that it can run all over the place. Then you might need to have it come on several times just to keep the water in one spot.

With drip irrigation you should apply all of the water it requires in one application.  If your drip irrigation is operating at the same time as your lawn is being watered then this is a big no- no. This is frequently why drip is operating in that ten to fifteen minute range. Lawns should be irrigated separately from trees and shrubs. 

In your case, If your drip system is applying 2 gallons per hour through the emitters then the plant is getting 1/3 gallon each time you water which is 2/3 gallon total every other day.  The larger the plant, the more water should be applied to it.  For a one foot tall plant try and give it about 1 gallon of water each time you irrigate.  If your plant is 2 feet tall then try giving it to a gallons of water each time you irrigate.  If plants are 5 feet tall, give them about five gallons of water at each irrigation.  This is a very rough estimate.  My sense is that you may be under irrigating.

Photinia after corrective action was taken
Photinia have another big a problem if they are growing in rock mulch.  In rock mulch, they tend to yellow and begin to scorch around five years after they have been planted.  The soil under the rock mulch has become mineralized and they can not take up enough nutrients to satisfy their needs.  You can try to supplement these mineral requirements by adding a good fertilizer once or twice a year and an iron chelate to the soil in about late January or February.  Try using a good quality fertilizer for trees and shrubs like miracle grow and add an iron chelate to the soil such as iron EDDHA.  It is hard to find and expensive but usually Plant World Nursery on Charleston boulevard carries it.

If a Sago palm is planted in a very hot location with lots of reflected light it can begin to yellow.  It can also begin to yellow if we have a very low winter temperatures.  You will see yellowing due to very cold low temperatures very early in the spring or late winter.  If it is yellowing because of a lack of iron then the iron chelate mentioned above will correct it.  If the yellowing is because of watering too often then you may correct it by correcting your irrigation and not watering twice each day but watering only once on the irrigation day but applying more water.


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