Plant id – Cup plant

(Question)

imageI have a giant plant growing in my garden and I have no idea what it is. I’m concerned it is a weed and perhaps a toxic or poisonous one, so I am looking for some help identifying it so u can decide whether to remove it or not and how. I have attached one picture. It is tall, about 7 feet. It has broad leaves that are long and have a good tip at the end. It doesn’t seem to be flowering. The stalks are abou 3/4″ thick, mostly green, though one is purplish. I did but a lot of native species seeds two years ago and I think perhaps this is one of them and maybe as it is the second year of growth that it is really flourishing. But I have no idea. Any help with this giant would be really appreciated!!! Thanks.

(Answer)

Thanks for sending your photos.  You have a cup plant or Indian cup plant (Silphium perfoliatum).  It belongs to the Asteraceae family. Water collects on the leaves where they attach to the stem, creating a ‘cup’ that collects water which birds love. The seed was likely included in your wildflower seed packet.

Silphiums are very large plants, most suitable as a back drop in a very large garden.  The plant spreads generously via shallow rhizomes or self seeds in moist, loamy soil.  You can expect yellow 2-3″ flowers soon.  Silphiums flower from July to October.

I am attaching a few web sites you might find interesting:

https://www.finegardening.com/cup-plant-silphium-perfoliatum

https://www.illinoiswildflowers.info/prairie/plantx/cupplantx.htm