Determining What's Wrong With Your Plants

Recognizing the early warning signs of plant disorders is essential for good pest and disease control.

Similar Topics:
Thirsty Bamboo

Thirsty Bamboo

Lack of water is a common cause of problems with plants grown in containers. Bamboos are notoriously thirsty and need regular watering to keep them healthy.

©2008, Dorling Kindersley Limited

2008, Dorling Kindersley Limited

Step 1: Check for Plant Disorders

Plants that look as if they are troubled by pests or have a disease, but are not visibly under attack, may be suffering from a “disorder.” Disorders happen when a plant lacks sufficient nutrients or water, or is growing under adverse conditions, such as excessive cold or warmth. They can also occur if plants are subjected to more wind or sun than they can handle, are growing in shade when they prefer sun, or have a poor root environment. 

Disorders are very common, and if the underlying problems are not rectified quickly, they often lead to an outbreak of disease or attack by pests, which take hold of the weakened plant. Plant disorders are not diseases, although the symptoms can look similar. Adverse weather, such as drought or unusually low temperatures, can affect plant health, although mature, hardy types often tend to recover quickly when more favorable conditions return. Young plants, or those that have recently been planted, are more vulnerable; you will need to keep a close watch on them, and protect them when necessary. Increase their natural levels of resistance by making sure you are growing them in a suitable site and soil.

Step 2: Check for Lack of Water or Nutrients

Lack of nutrients is a less common problem than you’d think; most tended garden soil has been fed over many years, topping off nutrient levels. Nitrogen, however, may be lacking, since it is easily washed out of the soil. A deficiency will lead to pale leaves and sickly growth, and can be remedied using a nitrogen-rich fertilizer, such as dried chicken manure pellets or sulfate of ammonia, and watering well. Organic matter, such as compost or manure, dug into the soil before planting or used as a mulch, will also boost nitrogen levels. 

Lack of water causes poor growth and flowering, as well as powdery mildew attacks. Without an adequate water supply, plants cannot take up enough nutrients from the soil. During prolonged dry spells, plants may turn brown and lose their foliage. Well-established woody plants have enough roots to ride out these dry spells and recover when rain returns. Lawns turn brown, but the living buds at the base of the grass remain alive, so they regrow when rehydrated. But plants with limited root systems, such as annuals and herbaceous perennials, are more vulnerable; cut back wilted stems, remove dead leaves, then water the plant well regularly. You should soon see new buds and stems emerge. Newly planted plants, especially trees, shrubs and climbers, are particularly vulnerable to drought and a lack of nutrients. To prevent problems, water them regularly, and keep the area around the roots free of weeds.

Step 3: Check for Lack of Light

Growing plants in shade when they prefer a sunny site will lead to pale or yellow leaves and stems, and poor growth. Plants and seedlings may grow tall and spindly, and lack vigor. The only cure is to move the plants to a location where they will receive the right amount of light.

Step 4: Check for Root Problems

When soils are waterlogged, dry, or airless, roots are more likely to contract fungal diseases. The first signs of root problems may be in the foliage; when roots are too dry, the leaves farthest from the roots turn brown, especially at the edges. Drought often causes the bark at the base of the stem to rot and die, too, although this is also a symptom of the root disease honey fungus. If the base of the stem is sound, check for dead roots that appear red or brown and brittle. If the root system is dead or damaged, the plant’s chances of survival are slim, but if roots are healthy, watering may save the plant.

Next Up

How to Treat Rust on Plants

Ugly—but seldom deadly—rust can be tough to eliminate. Follow these steps to treat plant rust and keep it from spreading in your garden.

Plant Diseases

Use these tips to learn how to recognize signs of stress and disease in your plants.

A Healthy Start: Learn How to Recognize Thriving Plants

Spotting the difference between healthy plants and failing plants will set your garden up for success.

Killer Plants

Some plants -- such as black walnut -- like to squelch the growth of other plants. Here's how to have a garden where all the plants get along.

Q&A: Wilting Tomatoes

Here is a tip on how to take care of your wilting tomatoes.

How to Plant Bulbs in Grass

Create a natural-looking display of bulbs in your lawn by adapting your planting technique to the size of the bulbs.

How to Reclaim a Weedy Yard

Grow healthy grass and say 'goodbye' to those nasty weeds with these simple and easy-to-follow lawn and gardening tips.

What Is Blossom-End Rot?

Blossom-end rot can be mistaken for a plant parasite or virus. It is usually caused by inadequate water and calcium in the soil.

Sudden Oak Death

A fungus-like pathogen is threatening not only oaks but many other woody plants. Here's a list of susceptible plants.

Happy Houseplants

Learn how to avoid the most common problems that can afflict houseplants.