Lupinus stiversii is a California native annual lupine found in the Sierra Nevada foothills and lower mountain slopes. Each flower carries distinctly bicolored petals — a yellow banner with pink to magenta wings — which is the source of the harlequin name. It was first collected near Yosemite in 1862 by Charles Austin Stivers and is increasingly available through native seed suppliers, though less commonly grown than hybrid annual lupines.
This species thrives in a Mediterranean pattern of cool, moist winters followed by dry summers. Fall direct sowing aligns with the onset of California's rainy season and produces stronger plants than spring starts. Like all lupines, it fixes atmospheric nitrogen through root nodules, leaving the soil in better condition for what follows. Seedlings resent root disturbance; sow in place. Deadheading slows seed set and can extend the display modestly, but plants self-sow lightly where summers are mild enough. Thin seedlings early rather than transplanting. Prefers low-fertility soil; rich soil produces excess foliage at the expense of flowering.
Lupine seeds across the genus contain quinolizidine alkaloids. The seeds of this species are not edible and are toxic to livestock and humans in significant quantity.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Lupin Anthracnose
Twisted, bending stems with sunken brown lesions; leaves develop dark spots and may collapse. Pink spore masses can appear on infected tissue in wet weather.
Remove and destroy infected plants. Use clean, treated seed and avoid overhead watering. Space plants for airflow and rotate planting sites to reduce spore buildup.
Damping Off
Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.
Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.
Fungal leaf spot
Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.
Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.
Mosaic virus
Yellowing, mottled, or distorted leaves. No cure — spread by aphids.
Remove and destroy infected plants. Control aphid populations to prevent spread. Do not propagate from infected tubers.
Aphids
Aphididae →Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.