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July 16, 2025 - Plants Signs and Signals

Identifying health issues in your yard and garden plants.

Most horticultural crops, whether annual or perennial, will inevitably encounter health challenges at some point. Most issues rarely appear overnight. Instead, plant problems typically develop gradually, offering growers a critical window to intervene if they know what to look for.

"It's rarely a case of a healthy plant suddenly dying in a matter of days," explains horticulturist Robert Spencer. "There are almost always earlier indicators that something isn't quite right in the garden."

These subtle warning flags, if observed, can provide valuable clues to problems that are developing. Effective diagnosis hinges on recognizing change, and without a clear understanding of a plant's healthy appearance, detecting shifts becomes impossible. This means that you need to learn what "normal" looks like for your specific plants at each stage of growth.

For perennial plants, you need to know their appearance when dormant, in full flower, and what constitutes an expected level of production. For annuals, it involves observing their emergence, growth and maturation. Across all plant types, familiarize yourself with typical colours, shapes and sizes. 

Initially, this baseline starts out as a theoretical picture, but with experience, it will become more real. "In short," Spencer advises, "you must watch your plants." Plants communicate their distress in a variety of ways, often through changes in their physical appearance. Recognizing these "signs and symptoms" can allow you to address issues early.

After seeding, most plants should emerge within two weeks, provided conditions are warm and moist. If nothing is sprouting, or if there are gaps, it could signal a problem with germination or emergence. While seed issues happen, human error in planting depth, spacing, or accuracy can’t be discounted. It's wise to wait a few days and then do a gentle dig around the planting area to reveal clues.

Once plants have emerged, keep watching. Are plants growing, or are they mysteriously vanishing or collapsing? A sudden disappearance or decline in health from one day to the next can indicate predation, such as by cutworms, or an attack by soilborne fungal pathogens. Size differences between adjacent plants can also be a strong indicator of trouble. It is important to watch for sudden size changes or deviations from normal.

Plants communicate their issues through colour changes, particularly those that occur out of season. A gradual fading or weakening of colour, often turning yellow, can suggest a nutritional deficiency, either due to root issues or soil deficiencies. A sudden shift, such as from green to purple or red, also signals a malfunction. In such cases, investigating the roots to assess their health is crucial, as a plant cannot thrive without viable roots, regardless of how many nutrients are supplied.

The location of the colour change is also significant. Are older, lower leaves changing colour, or are the young, new leaves affected? Is the entire plant changing, or only specific parts, such as leaf veins remaining green while the rest yellows? Additionally, watch for other abnormalities accompanying the colour change, such as bright red spots that are also crinkling, bubbling, or twisting. Are the colour changes associated with spots, holes, lesions, or other injuries?

Small holes or missing edges on leaves are often a clear sign that something is actively chewing on the plant. A thorough inspection – under leaves, in the topsoil, or directly on the foliage – can help identify the culprit. The nature of the damage and any visible pest life stages can provide crucial clues for identification and management. The timing of the damage's appearance can also offer valuable insights. An accumulation of sticky fluid on a plant, especially near a wound or hole, might indicate an infection or infestation. This could be sweet "honeydew" excreted by aphid colonies (often guarded by ants) during feeding, or fine webbing on leaf undersides, potentially accompanied by moving "sand" (mites). Sometimes, plants develop strange growths or swellings on leaves, stems, or other parts, ranging from tiny to quite sizable. If growth isn't significantly obstructed, they can often be ignored. However, for those seeking answers, cutting one open might reveal the cause. Often, nothing is found within, as the swelling is the plant's rapid tissue response to cordon off an infection or attack point.

Fungal pathogens often have visible growth stages on the plant surface, appearing as spores or other structures. These may have a distinct colour and may or may not be associated with rotted tissues. Any fuzz or unusual growths warrant a closer look for the underlying cause.

Abnormal tissue behaviour, such as twisting, curling, or swelling, can signal a plant is under stress. If a plant suddenly begins to grow oddly, a close examination is warranted. Consider recent events in the vicinity of the affected plant or plants. Was an herbicide applied nearby? Understanding the product's nature and mode of action is important. If using a plot of ground for the first time, research what might have been applied there in the preceding two to three years.

"While not all problems can be solved the moment they're discovered," Spencer notes, "catching them early significantly increases your chances of choosing a course of action that minimizes both short-term and long-term impact on your crops."

Pay attention to the subtle, yet powerful, signs your plants are giving you.