Listen to What Your Gardens Are Telling You

July 2nd, 2024

   Doctors can ask patients where and how it hurts to zero in on a diagnosis.

These astilbe plants are trying to tell that they’re not happy in full sun and dry soil.

   It’s not as straightforward in the landscape when you’re trying to figure out what’s going wrong with your plants.

   Although plants can’t talk or point, they are good at giving us clues. We just have to pay attention enough and be astute enough to interpret what they’re trying to tell us.

   This isn’t always easy, but the effort is worthwhile because it can prevent dead plants, keep you from wasting time and money on misguided treatments, and maybe most important, give information to help with future plant selection.

   Unless you catch a groundhog waddling away with your cabbage between his teeth, you’re usually going to have to rely on the garden’s two main ways of communicating stress – signs and symptoms.

   Signs are direct clues – things you can see that are likely causing trouble. That would include things like pepper-sized leaf fungi viewed under a hand lens, little brown “pellets” (rabbit poop) next to the chewed-off petunias, or leaves that have been chewed between the veins (caterpillars or beetles).

   Symptoms are tougher. These are how plants have reacted to a problem, which is hard because a particular symptom can be caused by several different issues.

   Wilting, for example, can happen because of lack of soil moisture, rotted roots due to too much water, animals chewing the roots, disease, intense heat, or over-fertilizing, to name a few.

   A good first step in diagnosing is to know what plant you’re looking at and what’s normal vs. abnormal for that plant.

   Many a gardener has panicked at seeing yellow needles on their white pines in fall when it’s normal for the inner needles of that species to do that. Ditto for bark peeling off Kousa dogwoods, birch, oakleaf hydrangeas, ninebarks, and other species that normally have peeling bark.

Wilt disease is a common problem that plagues clematis vines.

   IDing your plant can help simply because some plants have some very specific and very common problems. A few that come to mind are spider mites browning out the dwarf Alberta spruce, black spot disease on roses, and wilt disease on clematis.

   Don’t jump the gun and start spraying before you know what’s going on. Try to figure out what the problem is, determine if it’s serious enough that you need to intervene, and if so, then choose the least disruptive treatment to get the job done.

   Also helpful is paying attention to your landscape. Take regular walks to enjoy the plants, and while you’re gawking and sniffing, watch for early signs and symptoms of potential trouble.

   It’s much easier to head off a problem caught early than to try and cure/fix it after the trouble is full-blown.

   You might not know – and never figure out exactly – what’s troubling a plant, but taking action early enough sometimes is enough to save the day. A simple move to a different location or digging up a struggling plant and improving the soil can often prevent doom.

   A case in point in my yard is a line of liriope that I planted along a front walk. This bed gets full afternoon sun and has both junipers and a maple tree nearby that produce lots of root competition.

   I suspected liriope was a tough enough plant to deal with these challenges.

   However, deer and bunnies munched on enough of the clumps that I kept getting spotty deaths. I tried adding, dividing, watering more, and spraying repellents to give the liriope a fighting chance to establish, but the spotty deaths continued.

   That told me it was time to give up. The plants were saying they just weren’t “happy” with the situation, and so I moved the survivors and planted creeping sedum along the walk instead.

   These were divisions from creeping-sedum plants that already were growing well on the opposite side of the same walk. Odds are decent (although never guaranteed) that if the sedums were happy on one side of the walk, they’ll do well on the other side as well… and fit in nicely design-wise.

   We’ll see. But the lesson is that sometimes, as Kenny Rogers sang, you have to know when to hold ‘em and when to fold ‘em.

   Penn State Extension’s cadre of Master Gardeners is an excellent source of help once you notice something that’s not normal. Most Pennsylvania counties have them, and some, like Cumberland and Dauphin, have regular in-season hours when they man phones or clinics.

   Some garden centers also have staffers who can help ID a problem if you take a clipping or bagged bug in.

   Five other plant-problem diagnostic aids:

* The book “What’s Wrong With My Plant?” by Dan Deardorff and Kathryn Wadsworth (Timber Press, 2009).

* University of Minnesota’s “What’s Wrong with My Plants” website that lets you search potential problems plant-by-plant and by symptoms.

* Virginia Extension’s fact sheet on diagnosing plant problems.

* Ohio State Extension’s fact sheet on diagnosing sick plants.

* Penn State’s Plant Disease Clinic, where samples of struggling plants can be sent for free diagnosis.

   I’ve written a few other PennLive.com garden columns and website posts that also can help, such as:

* A PennLive column on common things that go wrong with landscape plants and how to prevent/fix them.

* A 19-page “George’s Survivor Plants for Pennsylvania” booklet that’s available as a $4.95 download through this website. It lists hundreds of what I consider to be the best plants and specific varieties for Pennsylvania yards along with key stats on each plant.

* Profiles of a few hundred of my favorite survivor plants. Those are posted by category in the Plant Profiles section of this website and free to read and save.

* Three sets of lists that offer best plant choices by the situation, such as plants least likely to be eaten by deer, ones that tolerate damp conditions, and ones that give the best chance of surviving on a hot, sunny slope. These also are free and posted on this site under Solution Gardening 1, Solution Gardening 2, and Solution Gardening 3.

* A PennLive column on why killing plants is a normal part of gardening… and why

   And for a few general guidelines, Penn State professor emeritus of plant pathology Dr. Gary Moorman developed this symptom checklist:

* Plant is yellowing all over: Poor soil fertility; extreme heat; light is too intense or lacking; plant is pot bound.

* Young leaves are yellow: Not enough light; iron or manganese deficiency in the soil; excessive fertilizer.

* Old leaves are yellow: Nitrogen, magnesium or potassium deficiency in the soil; overwatering; natural aging of leaves; plant is pot bound; roots are rotting.

* Random leaves or needles yellowing or browning: Mite damage; herbicide spray drift; root or stem injury; stem galls.

* Dead or yellow spots on leaves: Fungal, bacterial or viral infection; excessive fluoride in the soil; pesticide damage.

* Holes in leaves: Caterpillar, slug or other bug damage; fungal leaf spot disease; hail or wind damage.

* Mosaic pattern of light and dark green on leaves: Viral infection; excessive heat; pesticide damage; nutrient deficiency in the soil.

* Leaves brown around the edges: Wind damage; excessive salt in the soil; lack of water; excessive fertilizer; pesticide damage; air pollution.

* Leaves falling off: Excessive fertilizer; lack of water; reaction to move or transplanting; cold damage; pesticide damage; lack of light; rotting roots; natural life cycle of plant.

* Leaves wilted: Under- or over-watering; excessive fertilizer; roots or stems rotting; rodent damage to roots; pesticide damage; frost damage; excessive heat.

* Weak growth and/or gradual dieback of branches: Lack of water; root injury or girdling roots; compacted soil; plant was planted too deeply; excessive mulch; poor soil nutrition; lack of light.