How to discern exactly what malady is attacking your plants

What’s wrong with my plant? A slight change in appearance sends most of us scrambling to learn the cause of the change, whether we’re responsible and what we can do to remedy the problem, if the change is a problem.

We usually accept responsibility for the problem if the change is due to nutrient or water deficiencies. How do you discover what deficiency is responsible? First of all, if you have more than one plant, are all similarly changed? If so, it may be a pH problem. Where does this change appear? On older leaves (lower on the plant) or on newer (top and branch end) leaves? On the flowers? On its fruit?

Is the change of leaves, for instance, a change of color or shape? Curling, twisted and deformed leaves may mean the plant has a virus, perhaps curly top virus. Yellowing leaves may mean a deficiency of nitrogen, manganese, magnesium, iron or too much water or sun. If leaves at branch tips are yellowing but have dark green veins, it may mean iron or manganese deficiency. If the yellowing is on older leaves at the bottom of the plant, and veins remain green, that spells nitrogen or magnesium deficiency.

Foliar treatment with Epsom Salts (one teaspoon per pint of water sprayed on leaves) should cure the magnesium deficiency. Chelated iron spray when leaves first unfurl, before they’ve developed a protective coating, may help the iron supply. It’s very difficult to change the coloring of leaves discolored by iron deficiency, but such deficiencies occur often in our area, especially on fruit trees. I know a granular iron is available (Ironite), but I don’t use it because of its toxic ingredients — arsenic and lead. It’s made from Arizona mine tailings, banned in Canada and some reports claim it’s banned in Maine and Washington. California and Minnesota have also been questioning its safety

If leaves are yellow at the top without conspicuous green veins, the plant may fare better if it had at least partial shade during the day. If leaves are totally yellow at the base of the plant, and they’ve been frequently watered, back off on the watering. This often happens with citrus trees grown as houseplants. I’ve killed many citrus trees with overwatering. Use a moisture meter and don’t water until the meter reads one or lower. If watering has been ordinary, perhaps the plant is just old.

Plants such as rhododendrons, azaleas, blueberries and hydrangeas may be discolored because the pH of our soil is too alkaline for them. Loads of organic matter worked into the soil may lower the pH, and so will the addition of gypsum, but changing the pH from alkaline to acid requires either a lot of sulfur or planting the shrub in pure peat moss in the beginning. Rapid conversion of the pH by sulfur may be counterproductive if not done right. Consult your county extension agent for instructions.

Our water tends to be about 7.0 pH (neutral), still on the high side for some of those shrubs. Over time, this will raise the pH of peat moss-planted shrubs too. Fertilizers such as Miracid may be necessary in such cases.

This story was originally published June 8, 2016 at 1:06 PM with the headline "How to discern exactly what malady is attacking your plants."