Yellow Giant Hyssop
Synonyms of Agastache nepetoides (4) (Updated 3-1-21): Hyssopus nepetoides L., Lophanthus nepetoides (L.) Benth., Nepeta altissima Schrank, Vleckia nepetoides (L.) Raf.
Agastache nepetoides (L.) Kuntze is the correct and accepted scientific name for the Yellow Giant Hyssop. It was named and described as such by Karl Ernst Otto Kuntze in Revisio Generum Plantarum in 1891. It was first named and described as Hyssopus nepetoides by Carl von Linnaeus in the second volume of the first edition of Species Plantarum in 1753.
The genus, Agastache Clayton ex Gronov., was described by Johan Frederik (Jan Fredrik) Gronovius in the second edition of Flora Virginica in 1762. The genus was first named and described by William Derek Clayton and Mr. Gronovius gave him the credit in his validly published description.
Plants of the World Online lists 22 species in the Agastache genus (as of 3-1-21 when I last updated this page). It is a member of the plant family Lamiaceae with a total of 236 genera. Those numbers could change periodically as updates are made.
There are several links at the bottom of the page for further reading and positive plant ID.
I had been seeing this tall plant along the fence next to a creek in a friend’s woods while observing wildflowers. I went several times and decided I would go ahead and see if I could make an identification. Normally, I prefer more shade or a cloudy sky for good photos but that wasn’t going to happen on May 10. The sky was clear and sunlight was peering through the trees and the plants stem nearly glowed.
After taking several photos of this plant and several others, I went home, checked the photos and uploaded them on iNaturalist for a positive ID. It’s a great way especially when there are no flowers to go by. As it turns out this plant is an Agastache nepetoides commonly known as the Yellow Giant Hyssop.
Agastache nepetoides is a strong-stemmed perennial plant that multiplies from the base and from seed. Plants can grow to about 7 feet in height…
Depending on what site visit, its leaves are described as crenate-serrate to serrate, subcordate, lanceolate-ovate, and cordate-ovate. In layman’s terms, the leaves are somewhat heart-shaped with a rounded base and taper to a point. The margins are heavily serrated with rounded teeth (crenate-serrate). Leaves can grow to 6″ long x 3″ wide, the upper leaves and the leaves on branches somewhat smaller. The leaves have 2″ or so long stems (petioles). I didn’t smell the leaves (yet) but they are supposed to have a similar scent as catnip.
The strong stems are hollow, square, strongly 4-angled, and somewhat winged. Two opposite sides of the stems are somewhat concave which alternate at each node.
If you take a good look you can see hairs growing from the nodes…
The leaf undersides are somewhat paler to the upper surface due to fine hairs.
While the stems are pretty much hairless except for maybe toward the top, the leaf stems (petioles) are hairy (pubescent).
Plants branch out at the upper half of the leaf axils (at the nodes).
I just think the stems are neat…
Agastache nepetoides flowers from July through September so I have taken any photos of them yet. I am sure I have seen these plants on my own farm so I may be able to take photos here. Otherwise I will go back to the woods to take photos. I can write descriptions of the flowers better once I have physically seen them. Plants flower at the end of its main stem and branches, giving the whole upper part of the plant the appearance of a candelabra. The greenish-yellow flowers are tightly packed on 2-8″ spikes and only open a few at a time.
While not exactly a beautiful plant, it is planted as a pollinator in native plant gardens.
Plants, being perennial, come up from the base in the spring and also from seed. When seedlings reach 3-4 feet tall in mid-summer they will also flower.
A few websites mention it smelling like catnip and that the Iroquois Indians used an infusion made from Agastache nepetoides as a wash for poison ivy and itch.
I was planning on visiting the site where I saw this plant when it was supposed to flower but I didn’t get around to it. Maybe in 2021.
I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. My farm is in Windsor, Missouri in Pettis County (Henry County is across the street and Benton and Johnson aren’t far away). I have grown over 500 different plants and most have pages listed on the right side of the blog. I am not an expert, botanist, or horticulturalist. I just like growing, photographing and writing about my experience. I rely on several websites for ID and a horticulturalist I contact if I cannot figure them out. iNaturalist has been a great help. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.
I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. Some sites may not be up-to-date but they are always a work in progress. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at firstname.lastname@example.org. I would enjoy hearing from you especially if you notice something is a bit whacky
NOTE: Plants of the World Online is the most up-to-date database. It is very hard for some to keep with name changes these days so you may find a few discrepancies between the websites. Just be patient. Hopefully, someday they will be in harmony. 🙂