Greetings, caretaker. We, the lupines, stand tall and proud when healthy, our palmate leaves reaching for the sun and our vibrant flower spikes a beacon in the garden. But we are susceptible to a common and unsightly foe: powdery mildew. From our perspective, this is what it feels like and what we need from you.
The first sign is a subtle one. It begins as pale yellow or light green blotches on our upper leaves, a feeling of slight discomfort. Soon, the real invasion starts. A white or grayish, powdery film appears, first in isolated spots. This is the fungal growth, and it feels like a suffocating blanket, blocking our precious sunlight. As the infection progresses, this powder spreads relentlessly, coating our young leaves, stems, and even our budding flower stalks. Our leaves may begin to curl, twist, or distort as the fungus saps our strength. In severe cases, our beautiful green foliage turns yellow, then brown and crispy, as we are literally drained of life, our ability to photosynthesize severely compromised.
We do not ask for this affliction. The fungus (Erysiphe polygoni or others) thrives in specific conditions that are often beyond our control. Warm days and cool, damp nights create the perfect environment for its spores to germinate and spread. While we appreciate a drink, we despise having wet feet for long periods and abhor having our leaves drenched in the evening; this lingering moisture is an open invitation. Furthermore, when we are planted too closely together, the air stagnates around us. This poor air circulation allows the fungal spores to settle and multiply without being carried away by a breeze, turning our beautiful stand into a crowded infirmary.
Your prompt intervention is crucial for our recovery. At the first sign of the white powder, please remove and dispose of the most severely infected leaves. This helps stop the spread. For mild cases, many of our caregivers find success with a simple spray made by mixing one part milk with nine parts water. Applying this to our foliage seems to create an environment hostile to the fungus. Alternatively, a solution of baking soda (1 tablespoon), horticultural oil (1/2 teaspoon), and a gallon of water can alter the leaf surface's pH, inhibiting fungal growth. Please ensure you coat both the tops and undersides of our leaves for the best effect. For severe infections, you may need to apply a registered fungicide, but always seek the least toxic option to protect us and our pollinator friends.
Prevention is the greatest kindness you can show us. When adding new lupines to your garden, please seek out varieties that have been bred for resistance to this very disease. Give us space to breathe and grow; proper spacing according to our variety ensures good air circulation. When watering us, please aim the water at our base in the morning, so our leaves have time to dry completely under the sun. A layer of clean mulch around our base can also help prevent spores in the soil from splashing up onto our lower leaves during rain or watering.
