If you are like me, sometimes you look at a plant and think, “What is wrong with it?” When you have no idea what’s ailing a beloved plant, where should you turn?

I experienced this dilemma recently after planting a new salvia at the edge of my garden. The tall purple blooms could be seen from my kitchen window and added welcome color to a dark swath of fencing.

The plant flourished throughout the summer. Then winter came, and the salvia experienced a series of insect infestations. I eradicated one pest only to have it followed by another. Something must be weakening the plant, but what?

When faced with an unknown plant ailment, you need to assess the situation and the garden environment. Just like a medical doctor, you must consider all possibilities before making a diagnosis.

To begin, know what plant you are dealing with. Not all plants are susceptible to the same pests and diseases, and being sure of what you have is vital. Many people have struggled to identify a disease because they had misidentified their plant.

The University of California’s Integrated Pest Management website (ipm.ucdavis.edu) can be a big help. You can search for your plant and find its potential pests, diseases and common ailments. Many times I have been nearly panic-stricken about a beloved shrub, only to find an accurate diagnosis and easy remedy on this site.

What if things aren’t that simple? What if you don’t know the plant you are dealing with? At that point, I would recommend calling or visiting the Napa County Master Gardener help desk (address below).

Help-desk volunteers answer your questions and diagnose garden problems. Provide a detailed description of your challenge, and they will do their best to solve your problem. If you have photos or a plant sample, even better. The Master Gardeners on duty will ask many questions to try to determine the culprit. Often a seemingly dire situation requires little or no treatment. Sometimes an apparently straightforward problem is a symptom of another issue.

Get home and garden tips sent to your email inbox

That was the case with my salvia. I adjusted the watering, fertilized and treated the pests, but the plant still looked sickly. A fellow Master Gardener suggested that I inspect the broader environment. Eventually, I discovered a factor that I hadn’t even considered.

Unbeknownst to me, our neighbor’s gardener had been liberally applying an herbicide on the other side of our fence. During the summer, this had not been a problem as the herbicide generally didn’t stray. However, winter rains washed the chemicals into my garden soil. The diluted herbicide had slowly weakened the sage, making it easy prey for hungry insects. While I may not be able to change my neighbor’s behavior, I can salvage my sage by simply moving it.

So when you see a struggling plant and the cause is not evident, don’t get discouraged. The diagnostic tools you need are within reach. Get to know your garden and its surroundings, research all the possibilities and involve the local Master Gardeners. These steps can save you a great deal of time, money and frustration.

Workshop: Napa County Master Gardeners will hold a workshop on “What’s Bugging You?” on Saturday, June 18, from 9:30 to 11:30 a.m., at University of California Cooperative Extension, 1710 Soscol Ave., Napa. Understanding pests and blights that affect your vegetables is key to managing them. Squash that doesn’t grow, tomatoes with peculiar markings, artichokes full of earwigs, plants that fail to thrive − all these and more will be discussed. Bring your problems to show and tell, and learn how Integrated Pest Management techniques can help. Mail-in/walk-in registration (cash or check only). Online registration coming soon.

Subscribe to Breaking News

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.