GARDENER'S MAILBAG: Why are my mountain laurel's turning?
Dear Neil: My mountain laurel’s leaves turned brown in a matter of weeks. How did the fungus take hold? The small tree had been healthy for years. If I replant, what preventive measures should I take for a young plant?
Your e-mail pre-dates the extreme cold by a couple of days, so I can discount that as a cause. I don’t want to jump to the browned leaves and leaf spots as being the original cause of this problem (although I don’t have any better idea just yet). I would be more likely to suspect a trunk or root problem. I’m grasping at straws, but it appears that the walk is water-stained adjacent to the plant in your photo. Is there any chance that this plant has had water dripping around it for a prolonged period of time from the hose hanging on the wall? That could have caused it to die by killing its roots due to lack of oxygen. If you feel the plant has been lost (it appears that that’s the case), you might want to send a portion of the base of the trunk and a major root and some of the smaller roots to the Texas Plant Clinic at Texas A&M University in College Station and ask them to look at it. There is a charge for their analysis, but then you would know for sure. All the details are at their website. As for replanting, I would probably choose another type of plant just to be on the safe side.
Dear Neil: You often recommend eastern redcedar and other junipers for landscape screens. Are those the same plants as the “mountain cedars” we hear in the allergy reports?
In many cases, yes. Eastern redcedar (Juniperus virginiana) is the native conifer that grows over huge parts of Central and East Texas. There are thousands of acres that are covered with it and other species of junipers. They turn bronze and produce pollen from mid-winter into early spring and warm south winds push the pollen across the state. But lest you grab you grab your chainsaw and start taking out all your junipers, let me share a personal opinion. My wife suffers this seasonal allergy. Sprays help her immensely, and so I have left the 40 or 50 mature trees we have on our rural property in place. I even planted several more years ago to act as a critical privacy screen since I knew they would blend in and maintain the natural look. I figured the pollen those 15 trees would produce wouldn’t add much to the overall pollen count produced by the millions of other trees in the hundreds of miles around us. (That’s how far wind-borne pollen will travel.)
Dear Neil: I’ve been reading about ajuga as a flowering groundcover for the shade. Have you grown it, and would you recommend it in Texas?
Yes, I’ve grown it for 50 years, and yes, I’d recommend it, but with one very major precaution. It is a lovely low-growing groundcover for heavily shaded areas. That alone makes it really special. We don’t have that many good groundcovers for shade. The fact that it blooms makes it all the more special. The flowers, on most varieties, are stunning rich blue, one of the least common colors in the Plant Kingdom. And it spreads quickly, at least most selections do. But the problem is that it’s also highly susceptible to crown rot, a water mold fungus that can wipe out an entire planting in just a couple of weeks. I know, because my planting of bronze ajuga that I had propagated myself was struck by it and killed out completely in a 5-day period. I couldn’t get to the store, buy a fungicide and get it applied fast enough. I was out of the ajuga business before I knew it. I still grow ajuga, but I’m careful to plant it in perfectly draining soil, and I limit my plantings to small areas such as rock retaining walls and between stepping stones in little-used garden paths. It has thrived in those settings for 25 years.
Dear Neil: How soon will we be able to assess the damage the cold did to our landscape plants? What should we do to the ones that have turned brown?
Don’t rush to a judgment. If they have browned leaves, it’s possible that new leaves will be produced to replace them. You might have only minor dieback on some of the twigs with just a little pruning and reshaping to do. On the other hand, some shrubs will have been killed completely to the ground. That’s going to happen to oleanders in big parts of Texas, for example. Their twigs will turn brown along with the leaves, so you’ll have quick indication of the magnitude of your problems. With those plants, folks will have to cut them back completely to the ground. They will come back with robust growth from their roots. Other plants that are killed to the ground may not come back at all. Pittosporums in many parts of Texas fall into that category. So will star jasmine and loquats where they are grown. So, my suggestion at this point, because Texas is such a big state and because so many plants are involved, is that you just sit tight for a couple of weeks. As stem tissues turn brown and brittle, you’ll know they can be pruned off, but don’t rush to bad decisions.
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