Why Do My Marigolds Look Unhealthy?

Have the leaves of your marigolds been skeletonized and do the flowers seem to have been eaten?

Are the leaves stippled with yellow and is the foliage webbed?

Are the leaves curled and distorted, sticky to the touch?

Are the leaves discolored and distorted?

Are the leaves greenish-yellow and the is growth rate low?

Are the flowers of your marigold covered in gray mold?

Has the marigold's stem turned black at the base, and has the plant wilted?

Are there only a few blossoms, but the foliage is excessive?

Skeletonized leaves and eaten flowers of marigolds are caused by Japanese beetles. These insects devour leaves, stalks, and flowers of nearly 300 plant species. Their larvae feed on the roots of the plants. Handpick adult beetles into a can of soapy water but make sure to wear gloves as Japanese beetles are blister beetles. Apply parasitic nematodes to the soil to limit beetle grub populations. Use pyrethrin powder or neem oil as a last resort.

Leaves stippled with yellow and webbed foliage is caused by spider mites. These tiny, spider-like pests feed by sucking sap from the underside of the plants leaves causing yellow flecking on the upper leaf surfaces. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

Distorted and sticky leaves and stems are caused by aphids. These tiny insects can vary in color, green, pink, black, gray to completely white. They cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted, while leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used only with severe infestations.

Discolored and distorted leaves on marigolds are caused by leafhoppers. These small, green or brown insects feed by sucking juices from leaves undersides. Leafhoppers may be the carriers of bacterial of Aster yellows an incurable disease. Insecticidal soap helps with severe infestations.

Greenish yellow leaves followed by a poor growth is caused by Aster yellows disease. This disease is transferred by insects called leafhoppers. There is no cure for Aster yellows, so the affected plants should be destroyed. Prevent the disease by controlling leafhoppers. Spray the plants with the insecticidal soap 3 times, once every 3 days.

The likely cause for these symptoms is a fungal disease - Botrytis blight. Other symptoms include brown or black spots that may appear on leaves and petals. You can only prevent Botrytis blight disease by planting marigolds in areas with good air circulation. Water the plants so that the leaves can dry up before sunset. Infected plants should be removed. Spray weekly with a copper fungicide until the disease is under control.

Blackened stems and wilted plants are caused by Stem rot. This disease can be caused by both bacterias and fungi. Remove and destroy all infected plants. Thin plants to ensure good air circulation. Water marigolds from below so the foliage can stay dry. In cases of severe infestations, don't replant new marigolds in affected areas unless you have solarized the soil beforehand.

Marigolds respond to over-generous fertilizing or very rich soil by producing copious amounts of foliage and very few flowers. Limit feeding to one dose of slow-acting fertilizer dose per season. Plants with lush foliage will eventually produce blooms if they are not fed again.

If there are no blooms or blooms that have faded the reason is excessive heat or temperature changes. High summer heat may slow, or even stop, blooming on marigolds. Use 2 to 3 inches of mulch to lower soil temperature. Fluctuation in temperatures from hot to cold causes marigold flowers to become paler than normal.