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Thursday, January 5, 2012

My Shrubs Growing In Rock Mulch Turned Brown in November

Q. I now water once a week but my shrubs are looking like they might in the hottest part of the summer. Leaves look dry, burnt and falling off. My average shrub is about 3'x3' and receives 3-4 gallons per week week based on my emitters and time on. Did I cut back to much ? What should I do to try to revive them ?
A. Your watering sounds very appropriate and probably what I would have scheduled as well. You have to make sure, however, that the water which is scheduled to be delivered to your plants is actually getting there. Make sure you check for plugged emitters when the system is on. You should have a filter on your drip system even if you are on city water.

             It could be several possibilities. I have to walk through them with you because I don't know much about their previous history. For me, it looks like possibly watering, possibly collar rot at the base of the trunk where the rock mulch sits against the stem, it could be very low temperature damage as possibilities. If there were some very low temperatures just prior to that than this could be just that. If there were no low temperatures than most likely it is not. Then we have to look at watering issues including the rock against the trunk.

First determine whether the plant is dead or not. Bend some branches and see if they snap. If they are still supple and just have damaged leaves then it is a temporary setback and they will regrow and set new leaves in the spring. If they snap when you bend them, it may be dead. You will have to pull it anyway so start bending the branches and see how much of the plant is dead. If the amount is sizable, remove it. When you remove it look at the trunk where the rock mulch was resting against it.

Use a knife or your thumbnail and scrape the bark away from the trunk starting about an inch above where the rock mulch sat and down along the stem to the roots. Look to see if there appears to be a dark area or rotten area in the trunk or bark around the rock mulch line. If there is, then it is collar rot. Make sure on any new shrubs that rock mulch does not lay against the trunk or, in some cases, the plant was not planted too deeply. It should have been planted the same depth as it was growing in the nursery container. Nurseries don't have many plants this time of year because they are trying to reduce their inventories. You can look for a replacement plant but chances are you may not find one that you like until next spring when it gets warm. I hope this helps.

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