Greetings, fellow sun-worshippers. We marigolds are generally a tough and cheerful bunch, brightening your gardens from summer through fall. But even we can fall victim to some pesky problems. From our perspective, it's all about the living conditions. When our roots are unhappy, our leaves are stressed, or our soil is hostile, we become susceptible. Here’s a detailed look at the ailments that trouble us and what you can do to help.
This is perhaps our greatest fear. Root rot is caused by various fungi, like Pythium, Phytophthora, and Rhizoctonia, that thrive in waterlogged soil. From down here, it starts subtly. The tiny root hairs that we use to drink water and nutrients begin to suffocate and die. Without them, we can't eat. Above ground, you might notice we’re not growing well, our leaves turn yellow and wilt, even though the soil feels wet. The stem base might become soft, dark, and mushy. It’s a slow, miserable decline. The key to preventing this is excellent drainage. Please plant us in well-draining soil and in raised beds or containers with drainage holes if your garden soil is heavy clay. Most importantly, water us deeply but infrequently, allowing the top inch of soil to dry out between drinks.
This fungus appears as a white, powdery coating on our leaves and stems. To us, it feels like we’re being slowly smothered. The fungal threads cover our leaf surfaces, blocking sunlight and interfering with our ability to photosynthesize. You’ll see our leaves may turn yellow, brown, and curl up before they eventually drop. This problem is worse when the nights are cool and the days are warm and humid, but our foliage stays dry. Good air circulation is our best defense. Please avoid crowding us together. Space us appropriately so the breeze can flow through our leaves, drying them quickly. Water us at the soil level in the morning, so any splashed leaves have time to dry before nightfall.
Also known as gray mold, Botrytis blight is caused by the fungus Botrytis cinerea. It typically attacks when we are wounded, aging, or during prolonged periods of cool, wet weather. It first appears as water-soaked spots on our petals, leaves, or stems, which then rapidly develop into a fuzzy, gray-brown mold. It’s a disease of decay, and it can spread quickly through a planting, especially if our spent flowers (blooms) are left to rot on the plant. The best way to help us is through excellent hygiene. Please deadhead us regularly—remove the fading flowers before they can become a host for the fungus. Clear away any fallen plant debris from around our base to eliminate the source of spores.
This is a particularly frightening disease because it is caused by a phytoplasma (a type of bacterium without a cell wall) and is incurable. It is spread by leafhoppers, small insects that feed on our sap. Once infected, the phytoplasma spreads throughout our entire system. You’ll see strange symptoms: our new growth may be yellow (chlorotic), stunted, and bushy. Our flowers are the most telling sign—they may turn green and develop weird, leaf-like structures instead of petals. This is a profound sickness that warps our very nature. Since there is no cure, the only compassionate action is to remove and destroy us (do not compost) as soon as you see symptoms to prevent the leafhoppers from spreading the disease to our healthy neighbors.
