Rosinweed is very tall with long stems and somewhat sparse leaves, so it makes a great background for other midsummer to early fall perennials. The yellow, daisylike sunflowers are successful additions in pollinator gardens, native gardens, and naturalized areas with moist, well-drained soils and plenty of sunlight. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region and current research.
Size and method of spreading:
Rosinweed is between 2 to 6 feet tall and 1 to 3 feet wide. It spreads by self-seeding.
Native geographic location an habitat: (include C-value if appropriate)
The native range of rosinweed includes the Central United States. C Value: 5.
Attracts birds or pollinators:
Rosinweed attracts pollinating bees, butterflies, and birds.
The leaves of rosinweed have short hairs that give the leaves a sandpaper-like texture. The leaves are broadly to narrowly ovate and often reach up to 5 inches long and between 1 and 3 inches wide. The edges are smooth (entire) or have small teeth (serrate). Rosinweed leaves grow in opposite pairs with each pair at a right angle from the pair above and below (decussate).
Rosinweed produces yellow, daisylike flower heads that are about 2 to 3 inches in diameter. The flowers occur in branched clusters (panicles) at the terminal ends of the stems. As they are sunflowers, the flower heads orient toward the sun throughout the day. The 12 to 35 petallike ray flowers surround numerous disk flowers in the center. At the base of the ray flowers are tubular structures that contain yellow, stringlike structures with divided tips (styles). The inner disk flowers are green until they bloom and turn yellow. After they have flowered, the disk flowers are tubular and contain long, brown structures (stamen). Each flower head has a distinct group of overlapping bracts. They are broadly ovate, pointed, and dotted with glandular hairs.
The fruit of rosinweed is small, flat, dry, and does not open to release seeds upon maturity (achenes). The achenes of rosinweed are distributed by the wind. The achenes are produced only by the ray flowers.
Even though this is a tall perennial, rosinweed rarely flops or needs staking. This is a perennial that forms a deep taproot, and may be difficult to move once established.
List of pests, diseases, and tolerances:
Rosinweed may suffer from a fungal head blight of silphium, downy mildew, and leaf spot. The head-clipping weevil are pests that can cut off the flowers of rosinweed.