Rosinweed

The genus name, Silphium, has a Greek origin and refers to the resinous juice that oozes from a stem if broken. The species name- integrifolium, refers to the “entire or uncut leaves”. The common name, Rosinweed refers to the resin produced during blooming. It was used in a fashion similar to chewing gum by some Native Americans.

Silphium integrifolium is in the Asteraceae/Heliantheae family.

The large, bright yellow flowers are about 2 -3 inches across, although in years of drought, they may be smaller. The flower is composite, meaning it has both ray florets and disk florets. Ray florets are the ones we usually think of a petals. They number anywhere between 12 to 25. Each ray flower has a yellow to brown style that is split at its base. This is the fertile part of the flower. Prominent bracts with reflexed tips subtend each flower.

The main stem branches with each branch bearing multiple flowers. The flowers make nice cut flowers. Since there are many flowers to a plant, when you clip some for your vase, you won't miss them on the plant.

With a typical height from 3 to 6 feet, Silphium integrifolium is the shortest of the towering Silphium family. Rosinweed grows from a single stem that branches near the top to support many flower heads. The stout main stem is covered with stiff hairs. With such a stout stem, Rosinweed rarely flops. Interestingly, the stem color varies, sometimes being green and other times, red. I've noticed plants growing in a partly shady habitat tend to have the green stems with plants in a sunny habitat more often having the red stems. I find the red stems to be quite an attractive combination with the large green leaves.

Each pair of leaves are rotated 90 degrees from the previous pair. You can appreciate this in the picture above. The leaves are opposite and sessile (lack petioles). The shape is lanceolate or ovate. Leaf margins vary from smooth to slightly toothed.

Leaves are covered top and bottom with stiff hairs. This gives them a sandpaper-like, rough texture and they cannot be rubbed between the finger and thumb.

The seeds ripen in Autumn and are easy to harvest. New plants can be started by broadcasting seed and often bloom in their second year.

The plants have a tap root that helps them withstand drought. Rosinweed can form sizeable groupings through underground corms, but they aren't considered aggressive. Other plants easily grow among them. They do not release any type of allelopathic substance that would inhibit other plants from growing nearby.

The extended flowering of Rosinweed gives pollinators ample time to visit. Bumble bees, Sweat bees, Little Carpenter bees, Leaf-cutter bees and other bees are frequent visitors for pollen and nectar. Syrphid flies (such as the Virginia Flower fly shown below) and other insects seek nectar from the flowers.

Numerous types of butterflies, skippers and moths visit the flowers seeking nectar.

Occasionally hummingbirds, seeking nectar, can be seen flying quickly from flower to flower.

Growing well in both full sun to part shade, Silphium integrifolium is not a picky plant. It's found in prairies, glades and at the edges of rocky woods. It is one of our most drought tolerant plants, blooming well in hot, droughty summers. Extreme heat and drought may cause some buds to blacken and drop, preserving other buds to flower.

Rosinweed has a wide distribution from the East coast, west to Wyoming and New Mexico. Natureserve lists it as Critically Imperiled in 2 states, Wyoming and South Dakota. It has Vulnerable status in Kentucky and Imperiled status in Michigan. It is Apparently Secure in Mississippi. All other states within its range show No Status Rank.

In autumn and winter months, numerous songbirds can be seen consuming the seeds of Rosinweed. Some birds, such as the Blue gray gnatcatcher, use the stout stems of Rosinweed for perches while they hunt insects.