Answer a few questions about your plant and its symptoms. We'll rank the most likely causes — pests, diseases, nutrient issues, watering problems, or environmental damage — and suggest treatment steps. Takes about a minute.
We use this to filter out diagnoses that don't apply and to rank the most relevant causes. Not sure which category fits? Pick the closest match.
Pick the part of the plant where you see the main problem. If it's everywhere, pick "Whole plant".
Select everything that applies — the more symptoms you check, the more precise the diagnosis. You can select up to five.
These questions help us rank causes more precisely. Skip any you're not sure about.
Most plant problems fall into one of six broad categories: pests (insects and mites eating or sucking on the plant), diseases (fungal, bacterial, or viral pathogens), nutrient deficiencies or excesses, watering issues (too much or too little), environmental stress (sun, wind, frost, salt), and cultural errors (wrong light, buried stems, compacted roots). Knowing which category you're dealing with determines the fix — and misdiagnosing can make things worse. Fungicide won't fix a nutrient deficiency, more water won't help root rot, and fertilising a stressed plant often kills it.
The first useful skill is observation. Before you spray or feed anything, look carefully. Where on the plant is the problem? On new growth, old growth, or both? Leaves, stems, roots, or flowers? Is it uniform across the plant or on one side only? Did it appear gradually over weeks, or suddenly over days? Is only this plant affected, or the ones next to it too? These questions are the raw material for accurate diagnosis — and they're exactly what this tool asks.
Plant tissue behaves differently at different ages, and many diagnoses hinge on which leaves are affected. A nutrient that moves within the plant (nitrogen, phosphorus, potassium, magnesium) will be pulled from old leaves to support new growth when supplies run short — so the oldest leaves yellow first. A nutrient that doesn't move (iron, calcium, boron) gets stuck where it was originally delivered, so new leaves show deficiency symptoms first. That single distinction alone can tell you whether you're looking at nitrogen deficiency or iron chlorosis, two problems that look superficially similar but need opposite treatments.
Similarly, symptoms on one side of a plant only (or one branch only) usually point to localised damage — severed roots, pet urine, herbicide drift, or a borer in that particular stem. Symptoms spread uniformly across the whole plant suggest systemic issues — disease, watering, or nutrition.
Pests usually leave physical evidence: holes in leaves, webbing, honeydew, bite marks, frass (insect droppings), or visible insects. Diseases tend to produce coloured lesions — black spots with yellow halos, water-soaked patches that collapse, powdery coatings, or fuzzy growth. Both can occur on the same plant simultaneously, especially when sap-sucking pests create wounds that let fungal and bacterial pathogens in.
A quick diagnostic habit: check the undersides of leaves with a hand lens. This is where most pests hide and where fungal pustules first appear. If you can see fine webbing, moving specks, or bright-coloured bumps, you're likely dealing with a pest. If you see pale fuzzy patches or rings of concentric dark spots, you're more likely dealing with a disease.
A significant proportion of plant failures are cultural, not caused by an identifiable organism. Common culprits include planting too deep, burying the root flare, mulch piled against the stem, roots circling in a too-small pot, soil compaction after construction, pH mismatched to the species, and incorrect light exposure. These problems are often missed because gardeners look for active threats (pests, diseases) rather than passive ones (conditions). When symptoms don't match any pest or disease pattern cleanly — and especially when a plant is in decline without a clear cause — check the basics first.
Not every symptom needs immediate intervention. Seasonal leaf drop, normal flowering cycles, and cosmetic damage from minor insect activity often resolve without any action. Acute problems — severe wilting, rapid spread of disease, structural damage — need fast response. Chronic cultural mismatches (wrong site, wrong pH, wrong light) usually can't be fixed by treatment; the plant either needs to be moved or replaced. The honest answer for many declining landscape plants is that the species was the wrong choice for the site. No amount of feeding, watering, or spraying will fix that.
Gardening is a diagnostic profession. The more carefully you observe, the fewer times you'll reach for a spray bottle — and the more likely your interventions will actually solve the problem.
It's a diagnostic aid, not a definitive answer. The tool covers the most common causes of the most common symptoms in garden plants — it will usually narrow the possibilities to two or three genuine candidates. For confirmation, especially on valuable specimens, we strongly suggest taking clear photos of the symptoms and consulting a local horticulturist, arborist, or your state's agricultural department.
The tool is especially useful when you know there's something wrong but you don't know what to search for. Putting symptoms into Google without a diagnosis name often produces too many irrelevant results; this tool inverts the process — describe what you see, get a shortlist of what it could be.
First, select multiple symptoms if you're seeing multiple things — the tool weights diagnoses higher when several symptoms match. If nothing feels right, the problem may be:
(1) A less common pest or disease specific to your region — worth photographing and showing to a local nursery or extension service;
(2) A combination of multiple simultaneous issues — stressed plants often suffer two or three overlapping problems;
(3) A cultural issue that doesn't have obvious symptoms — wrong pH, nutrient lock-up, or root damage from earlier construction work;
(4) Something unusual like a virus, which is often difficult to diagnose without a lab test.
Those labels reflect a likelihood score calculated from how well the diagnosis matches your selected symptoms plus your answers to the follow-up questions. A Very likely diagnosis matches most or all of your selections closely. Likely is a strong match with some gaps. Possible means the diagnosis fits the symptoms you selected but other factors (follow-up answers, plant type) weren't a perfect fit. Worth checking is a weak match that's still worth ruling out — especially if your symptoms are vague or you answered "unsure" to most follow-ups.
The important thing: several diagnoses often rank "Likely" simultaneously. That's expected — plant symptoms overlap between causes. Read through the top 2–3 and see which plain-English description best matches what you're seeing.
The tool lists treatments in order of preference — typically: cultural/physical fixes first, low-impact sprays (oil, soap, biological controls) next, and harder chemistry last. For most home garden problems, the first two categories are sufficient. Chemical sprays should be a last resort because they disrupt the beneficial insects that usually keep pest populations in check.
We don't name specific brands — product formulations and registrations change frequently. When you go to buy something, read the active ingredient and the registration label, and ask your local nursery or agricultural store for the current-registered product that matches the suggestion.
Because these are genuinely common causes of plant decline that people overlook. Mulch piled against a trunk (a "mulch volcano") rots the bark and is probably the single most widespread cause of slow landscape tree decline in Australian suburbs. Construction damage to tree roots often shows up months or years later as dieback. Pet urine causes the characteristic yellow patches in lawns that everyone recognises but nobody wants to admit to. If one of these applies to your situation, the tool weights the matching diagnosis much higher.
Not necessarily. Many evergreens — including citrus, gardenias, magnolias, and camellias — drop a proportion of their oldest leaves each spring or early summer. Deciduous plants drop everything in autumn. If the leaf drop is confined to the older, interior leaves and happens annually at roughly the same time, it's likely a normal cycle. If new leaves are dropping, leaves are dropping unseasonably, or the plant is dropping heavily all at once, something else is going on.
Run the tool once per distinct problem. If you're seeing yellowing leaves on your citrus and chewed leaves on your roses, those are almost certainly two different issues, and combining them will confuse the diagnosis.
But if several plants in the same area are showing similar symptoms, the follow-up question "multiple plants affected at once" is useful — it points toward environmental, soil, or watering causes rather than something plant-specific.
Completely free, no signup, no ads. If you find it useful, a link back to Cape Nursery is appreciated but not required. Landscape designers, teachers, garden bloggers, and commercial nurseries are all welcome to use it as a diagnostic aid.