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Friday - February 24, 2012

From: Bethesda, MD
Region: Mid-Atlantic
Topic: Non-Natives, Poisonous Plants, Shrubs
Title: Problems with shrubs by pool in Bethesda, MD
Answered by: Barbara Medford

QUESTION:

We are trying to grow Otto Luyken Laurels by a pool and doing okay, some brown spots on leaves, but not many. Also have Arbivatea beside the pool about 3 feet from the edge of the pool. They have a lot of internal dying near the trunk. The rest of the leaf looks ok, but have some tip browning as well. 1 or 2 have some dead branching at the bottom. Do Arbivatea and Laurels do okay at a pool side? What nutrients should I give them to overcome the effects of salt water?

ANSWER:

Did you mean "arborvitae" instead of "Arbivatea" as we could find nothing on the second name anywhere, in or out of our Native Plant Database. There is, however, Thuja occidentalis (Arborvitae), which is native to Maryland, and we hope that is your shrub.

There are a number of plants with "laurel" in their common names that are native to North America, which is the area of interest for the Lady Bird Johnson Wildflower Center and Mr. Smarty Plants. However, apparently what you have is Prunus laurocerasus 'Otto Luyken,' which is native to southwestern Asia and southeastern Europe. It is sometimes referred to as "cherry laurel" or "English laurel." There are a number of shrubs native to North America with "laurel" as part of their common names, but Prunus caroliniana (Cherry laurel) is the only one that is also a member of the Prunus genus.

WARNING: The seeds, twigs, and leaves of all Prunus species contain hydrocyanic acid and should never be eaten.

Without knowing the full situation in your poolside garden; i.e., how much sun does the area get, how much of the shrub roots are paved over, etc. it is hard for us to make any judgment on the brown spots or the internal dying of branches. We did find this article on Brown Spots on Leaves that has several links with pictures that might help you diagnose that problem.

Since the arborvitae is native to North America, we will start with what information we can find on it. From Ohio State University, here is an article on Thuja Occidentalis. From that, we have extracted this information on "Foliage."

Foliage

  • sprays of scale-like, dark green, miniature leaves are evergreen and held so tightly against the stems that the young twigs are often completely hidden
  • old foliage from the self-shaded middle of the shrub abscises noticeably in Autumn, and falls through the interior of the canopy directly to the ground below, forming a light brown carpet that is easily raked up
  • the remaining foliage on most of the cultivars turns to an unnattractive chartreuse-brown in the coldest portions of Winter, but thankfully returns to medium- or dark green by late March

As we read up on this plant, we learned that it can get very large, and is somewhat messy, dropping needles and cones. Perhaps it might be a little large for a pool environment.

Prunus laurocerasus is not in our Native Plant Database, so we have looked at this Virginia Tech article on it, from which we have extracted this line:

"Cherrylaurel is a good plant to use near the ocean because of its tolerance to salt spray."

That is as near as we have come on either plant on toleration of salt-filtered pool water. So, we will look a little further at salt water pools, with which we are not familiar, and see if we can get any more clues. We found this article from Dave's Garden, Tips for Planting Around the Pool, which included this statement:

"However, unless you put an inordinate amount of chlorine and other chemicals in your pool, the amount of damage caused by treated water splashing on your plants will be minimal. Same goes for salt water system pools."

 

 

 

 

 

 

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