Plant ID: Silphium terebinthinaceum

copyright: chambersdesign || photo by: Aimee Ryan

If you have ever searched for a perennial that is more than the typical perennial, Silphium terebinthinaceum is your destination. This plant provides both the visual and dimensional explosion of incredibleness that, maybe, no other perennial can deliver. Far too many times when investigating the plant online, the only thing a post will show is its flowers. To only know about its flower is like only knowing about the sand of a beach along the coast of Sardinia but never seeing the water. You just aren’t seeing the whole picture. The leaves of this plant are as big as watermelons and give it a status within a garden that lasts for months and months and months.

What to Know

This cultural obsession with flowers is perhaps why we needed the Dutch New Wave in the first place. For centuries, it seems that only a very short list of plants have been prized for their colorful petals - and everything else has been disregarded. Even in the New Perennial Movement, far too many times, gardeners agonized about the hue of a flower in bloom. Don’t get me wrong, flowers are spectacular - but sometimes we gotta slow down and marvel at the leaves. And for the Silphium terebinthinaceum, the leaves leave nothing behind. They unfurl as spring comes into the picture and grow longer and wider as each day ticks away until they resemble the ear of an elephant or a kite hooked to the ground. For most of the season, you get to simply enjoy the leaves flowing in the breeze, but somewhere in late June or early July, the flower stalk does appear. Like slow motion rockets they inch toward the sky until they are around 10 feet tall. And just as the heat of summer is at its azimuth, the buds turn into blasts of yellow daisy-like puffs. Best used as an anchor plant - one can hold court, but a grouping of 3 to 7 (depending on available space) are better. These plants are not easy to find. I always have to cultivate them myself. They are worth the effort. And speaking of effort, they do need to be babied a bit the first year or so after planting. They have to develop a taproot before they really display their beauty. Once they have established, they need almost nothing…and like many native-ish plants, kinda prefer you leave them alone.

general information

Exposure: Sun

Soil:Average to Moist

Height of Leaves: 15 to 28 inches

Flower Height: 36 to 120 inches

Spread: 12 to 28 inches

Hardiness Zone: 4 - 9

Bloom Time: Late Summer to Early Fall