Magnolia acuminata, commonly known as the cucumber tree, is one of the largest and hardiest of the native North American magnolias. Named for its unripe greenish fruit that resembles a small cucumber, this deciduous tree produces subtle yellow-green blooms in late spring that are often hidden among the emerging foliage.
Unlike its showier southern relatives, the cucumber tree is prized as a shade and specimen tree for large landscapes. It thrives in cooler climates and provides excellent fall color, with leaves turning golden yellow before dropping.
Verticillium Wilt
Lower leaves yellow and wilt, often on one side of the plant, with brown streaking in the stem and crown tissue when cut open. Plants are stunted and decline over the season.
Remove and destroy affected plants. Avoid planting in soil that has grown infected tomatoes, peppers, or other susceptible crops. Rotate beds and improve drainage; there is no cure once a plant is infected.
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.
Magnolia Scale
Neolecanium cornuparvum →Large brown or pinkish bumps clustered on twigs and young branches. Sticky honeydew coats leaves below, often followed by black sooty mold and stunted growth.
Prune out and destroy heavily infested twigs. Apply horticultural oil to smother crawlers in late summer and dormant oil in early spring. Monitor annually since populations rebuild slowly.