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Wednesday, October 2, 2013

Plant Podocarpus With Leaf Scorch May Be Too Much Water

Q. I planted six Podocarpus (Fern Pine) in March, three by the north wall and three by the south wall. Now the three on the north wall have leaves that are turning brown. The three on the south wall are fine. I just didn't realize that the trees would get this much sunscald.  Any suggestions on what I can do, besides give them macronutrients and hope for the sun to change course?

Readers podocarpus with leaf scorch

Podocarpus showing very little podocarpus

A. Judging from the picture you sent showing the leaves turning brown, I really do not think it's going to be a continuing problem for you on the north wall once this is corrected. The south wall will be more of a challenge. I do not think this is sunscald but it is either a lack of water, watering too often or a lack of soil improvement at the time of planting.

            Since the problem you are having seems to be on the north side and not the south side, I might guess that you are keeping the soil too wet on the north side or they are not getting water.

            The north side and the south side are radically different micro-environments. It is much hotter on the south side than the north side. This means plants on the north side should be watered less often than plants on the south side.

            Notice that I said less often. The plants on both sides should receive the same amount of water but the difference should be in how often they are watered. To accommodate this difference in frequency of irrigation, plants on the north side should be on a different valve or circuit than plants on the south side.

            In the first picture it looks like you have rock for surface mulch. That will be a mistake for these plants in the future. It will be okay for a year or two but you should consider changing this out to wood mulch instead of rock.

            If you are going to have problems with this plant, it will be on the south side. These plants will tolerate a little bit of drought and infrequent watering so treat them like landscape trees and shrubs with deep but infrequent waterings.

            In other words, do not water them daily. At these temperatures, as long as you have good drainage, twice a week with about 10 gallons for each plant should be adequate on the south side if they are on drip emitters.

            On the north side, once a week would be adequate. If they are on drip emitters, they should have an emitter on each side of the plant. Put the emitters towards the front of the plant as far from the foundation as possible.

            There is a lot of calcium sulfate or gypsum in our soils. Adding water to soils high in calcium sulfate can increase corrosion on concrete.

            After mid-October you can cut your watering to once a week or longer but the same amount of water. In mid-December you can water these about every 10 days.

            These are evergreen plants so the damage will not disappear until new growth covers the damage to the leaves.

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