Diagnosing Outdoor Plant Problems

When you have a plant that is not doing well, you want to help it recover. Sometimes it is obvious what is causing the problem, but often it is not. Here is a checklist of things to go through to diagnose your plant's problem.

Just Transplanted or Established?

If your plant has been recently transplanted, it may be suffering from transplant shock or inadequate water. Transplant shock results from being moved and having the roots severed when the plant is dug up from where it was growing.

Inadequate water can cause the plant to wilt or have brown on the leaf edges. Plants should be watered the whole first year after they are transplanted. It takes that long for the roots on the plants to fully infiltrate the soil outside of the planting hole. Before a plant is established, it has to rely on the moisture in the soil inside the planting hole. After the plant is established, it can reach more soil and hence more water.

Anything Happen to the Plant Recently?

Has the plant or the area around the plant been sprayed or fertilized recently? What about construction or moving soil around in the area? Plants that have been sprayed may be reacting to the spray. If you spray plants with horticulture oil, for example, when the weather is hot, the oil will burn the plant. If herbicides were used nearby recently, could the spray have drifted onto the plant and injured it? Plants that are fine then have brown dry leaves or leaf margins within a few days after being fertilized are suffering burn from too much fertilizer.

Construction can put additional soil on tree roots and cut off their oxygen. Spilled or deliberately placed concrete can restrict the plant's roots. Be especially careful doing construction around existing plants.

Any Unusual Weather Recently?

Extreme heat or cold can cause plant problems, as can prolonged rain. Two or more weather conditions can work together to doom plants. For example, trees growing in a place with an extreme drought cannot cool themselves when the weather becomes extremely hot. Trees can die from an extreme weather event three to five years after it happens due to the stress such an event causes.

Cold weather can also cause problems. If the weather has been mild and plants have not gone dormant, a spell of extreme cold can kill the plants. Last year in my area we had no winter except for one spell of about 72 hours. It was extremely cold for my area those few hours and many plants died because they were all leafed out and not ready for the cold.

Flowering plants can drop their blossoms if it freezes after they bloom. For fruit trees like peaches or plums, that means no fruit that year.

Animal, Mineral, or Vegetable?

If none of these causes reveal the culprit causing your plant's problems, it is time to take a close look at the plant. What damage exactly do you see? Are the edges of the leaves brown, are there holes in the leaves or stem? If they have holes, are they chewed, round, or some other shape?

If you see pests, where exactly are they on the plant? Some pests love new growth, others go for the crown of the plant, and some eat the fruit or seeds. The first symptoms of some diseases are strange growth at the tips of branches.

Look at the area around the plant and look at any other plants closely related to the species of the problem plant. If lots of the plants around the problem plant also have the same problems, you are probably looking at a nonliving problem. If only the plants that are closely related to that plant are having problems, you are probably looking at a living cause for the symptoms.

If the growth on the top of the plant is wilted or stunted, this generally points to a problem with the roots. When plants cannot absorb water or nutrients naturally, the fastest growing parts are the first parts affected.

Spread or Static?

Is the problem spreading on the plant? Is it spreading from one plant to another adjacent plant? If the problem on the plant does not seem to be growing, your plant was damaged by a nonliving cause. If it is spreading, you are probably looking at an environmental cause.

Living Problems

If you think the problem is living, take a magnifying glass and carefully go over the affected part of the plant. While some pests are microscopic, you will probably be able to see something where the plant is damaged. Take note of the color of the pest, any patterns on it, the mouthparts (if you can see them), and whether there is more than one kind of pest present.

Look at the damage the pest is causing. Chewing and rasping pests eat the foliage or tear holes in it. Sucking and piercing insects suck the juice out of plants and cause white spots where the chlorophyll is missing. They also inject the area with toxins, so tissue death may occur around the feeding area.

Note that plants that are hosts for caterpillars, such as butterfly weed, will have some damage such as chewed leaves and missing leaves. You can't have butterflies without tolerating caterpillars on your host plants.

Fungal diseases can cause round leaf spots, stem rots with a dry/papery texture, concentric rings, discoloration, or wilt. Bacterial damage can cause galls (swollen areas in the twig or leaf), wet rots, irregularly shaped leaf spots, wilting, yellowing, or death. Viral diseases can inhibit chlorophyll formation, causing degrees of yellowing or mottling, stunting, distortion, or dieback of part of the plant.

Nematodes are microscopic roundworms that cause damage that mimic diseases. Root nematodes damage roots so they cannot carry water to the rest of the plant. Other nematodes damage other parts of the plant.

Nonliving Problems

Mechanical damage to a plant is usually apparent when the plant is examined closely. Broken twigs, wounds caused by weed trimmers or mowers, and crushed foliage are all types of mechanical damage you might see.

Physical factors are usually caused by extreme heat or cold. Moving a plant like a lemon tree from a low light area to a high light area, or vice versa, can cause the plant to drop foliage and blooms. Change light intensity gradually.

Oddly enough, both drought and excess moisture have the same symptoms. Leaves turn yellow, may drop off the plant, and the plant may wilt. Root rot is usually caused by too much moisture. Since the roots are not able to take up water, the rest of the plant acts like there is a drought.

Fertilizer, pesticides, and herbicides can cause leaf burn, distortion, chlorosis, or bleaching. Herbicide and pesticide drift from another yard can cause a lot of damage, so check the wind direction and expect a cone shaped damage area from the point of application.

Nutrient deficiencies or excesses can cause yellowing, the death of foliage, browning of leaves, and in extreme cases, death of the plant. For example, beets cannot tolerate much boron in the soil, or they won't grow right.

Next Steps

Gather the information you have gotten from examining your plants. Consult an expert such as your Extension agent or our nursery staff. Garden Plants Nursery staff are gardeners and can advise you on what to do next. Give us a call at 931.692.7325 for questions and orders.