Being A Plant P.I.

One day, your favorite rose plant is fine and full of buds, just waiting to burst. The next day, the leaves are wilted, the buds are drooping, and the plant seems to be on death’s doorstep.You faithfully tend your tomatoes all summer, doing everything by the book, then, one day, it rains—and the next day, every tomato plant in your garden has brown lesions and white fuzz on the foliage.

After a mild winter, the most important feature maple tree on your property leafs out, looks great—and then, for no apparent reason, it defoliates, dropping every single leaf, and dies.

Your lawn has looked great for years, but this year you notice a nearly perfect circle of dead grass that gets larger by the day. The grass on the outside of the ring is lush and thriving, but in the inside of the circle it now looks like a desert wasteland.

These are just a few of the mysteries that homeowners and gardens get hit with every year. To a horticulturist, some of these maladies are easily diagnosed by hearing about or seeing the symptoms, but in some cases the answer to the question “why?” isn’t simple to come by.

I’ve seen gardeners and property owners get downright irate and abusive when they don’t get an immediate answer; I wonder if they react the same when their doctor hears symptoms of their illness and says that tests are needed for a proper diagnosis?

In the plant world, diagnosing problems often requires something I call collaborative inquiry. The patient can’t be depended on for information, but you actually have lots of information, and whoever will be doing the diagnosis will either know the answer (or claim to) or will have to collaborate with others who may.

I’ve always enjoyed doing this kind of research and detective work. So much so that, more than 20 years ago, I was doing work that required me to get my private investigator license, and being a plant detective has striking similarities to being a PI. You need to hone your investigative skills, develop resources, and know who to ask and who to trust.

One series of plant mysteries that I’ve been trying to solve for more than 10 years is the issues I have with the common garden phlox, or Phlox paniculata. Why do some get powdery mildew and others not? Why do some get leaf spots and others not? How can I ever get control of the two spotted spider mites that seem to show up every year, but not on every plant? And why do the leaves curl on only one of my plants but none of the others?

I’ve read, I’ve experimented and I’ve endlessly pestered two colleagues, a plant pathologist and entomologist, whom I work with.

As anyone will tell you, the powdery mildew issue is related to moisture, the presence of the mildew spores, and how long the foliage stays wet and at what temperature. And yet, some phlox never get mildew, some get it every few years, and some may go five or six years without a spot, then bam … there it is.

By this time in the season, I usually have issues with two spotted spider mites on several varieties. I’ve tried chemical and organic remedies, and yet certain varieties tend to get the mites, while others don’t. It’s pretty clear that this is due to the leaf chemistry that is unique to every variety. But this year, I don’t have a single mite on any of my 10 phlox varieties.

What’s changed? Well, last fall, I removed every sign of leaves and stems at the end of the season (good garden sanitation), then I used a propane torch and flamed the crown of each plant to see if the flaming would eliminate any chance of over-wintering mite eggs or adults. So far, not a single mite has shown up.

Can I draw any conclusions? Well, not really, because I don’t have any control plants that weren’t flamed, so to attribute the lack of mites to the flaming process could be a dangerous supposition. Interesting, though.

I examine the phlox foliage once every week by walking through the phlox plants and randomly removing a leaf from the tip of the stem and one lower down on the stem. I use my 10-power loupe and methodically search the leaf for spots, movement or damage, and this year I did discover two things. On one leaf I spied a thrip, and on another plant I found two aphids. I’ve never seen either of these insects on phlox.

So, a new mystery evolves, and the detective work continues. Why this year? Why these insects? And is there any history of these two on this plant genus?

Thrips can be devastating to foliage and buds, and it’s rare to catch them in the act. They are usually diagnosed after the fact by their characteristic damage, and by then it’s usually too late to make any treatments. And my consulting entomologist told me that, yes, there have been reports of aphids on phlox, but it did seem unusually early when I spotted my two in April.

Yes, I have a few resources that you might not have at your fingertips. But if you want answers to your plant maladies, you need to know where to look and whom to ask.

You might think that your local garden center would be a good place to start, and, yes, some of the staff can be very helpful. But if you’re really serious, you need to have some resources of your own. These can be books like Pascal Pirone’s “Diseases and Pests of Ornamental Plants,” or the “Ball Guide to Diseases of Annuals and Perennials.” “The Garden’s Guide to Plant Diseases” and “The Gardener’s Bug Book,” both by Barbara Pleasant, and the dated but still relevant “Gardener’s Bug Book” by Cynthia Westcott.

And another resource, if not the best, is the Cornell Cooperative Extension of Suffolk County (631-727-4126, weekdays, 9 a.m. to noon). The extension office can do over-the-phone diagnosis, can suggest other resources as well as literature, and they may ask you to send them samples or pictures of your problem(s). They also have direct access to the Long Island Horticultural Research Lab, where there are insect, disease and weed experts they can use.

I actually was able to hook an Amagansett reader up with two researchers recently, where Eastern red cedars were mysteriously dying. You also can have insect and disease issues diagnosed by the labs at Cornell. There is a fee for this; you can find the information at /tinyurl.com/y7ha3jgn and /tinyurl.com/zdlcebk.

To begin your own detective work, here are some things to look for and consider:

Where did you buy the plant? How long have the symptoms been visible? Could it be related to drought? Remember, we’ve just gone through a three-year drought, and some issues we are seeing now with mature trees and shrubs are related to drought stress.

Did you spray something that the plant might have been sensitive to? Did you spray on a sunny, hot day? Has an herbicide been used nearby? Has fertilizer, especially chemical fertilizer, recently been used?

Is there a visible insect? Can you see if the insect has six or eight legs?

Has there been recent construction nearby? Do you use well water or municipal water? Have you recently pruned the plant? Is the plant near a road or highway where salt or brine is used in the winter? Is your lawn from seed or sod?

And when all else fails, or you just need some quick advice, you can drop me a line here. But, keep in mind, from April through July, I’m just as busy as you and it may take a few days to get a response.

Be a resourceful detective. Observe, record, ask … and, of course, keep growing!