Collecting yellow giant hyssop seeds

Yellow giant hyssop (Agastache nepetoides) is a State Threatened species that is found in open woods and savannas. We have had it growing fairly well for about 10 years and have contributed seed to some other savanna restorations in southern Wisconsin. It is found in only a few counties in the southern part of the state, and even in these counties it is not very common.

Our seeds came from a Dane County source. When we first planted, this species grew very well, but then seemed to fade out. This year it is back again, and there are enough plants so that we can collect seed.

This plant is in the snapdragon family, and the small flowers are not especially showy. When seed formation occurs, the seed receptacle opens but the tiny seeds remain inside in a cup-shaped structure and slowly sift out. This gives a clue to how to collect the seeds. You cut the seed heads off carefully, holding them vertically, and then carefully turn them upside down into your collecting bucket. A lot of the seeds spill out then and can be seen in the bottom of the bucket (see photo below).

Not all the seeds are released in this way, and the rest must be removed by handwork or with a hammer mill. Once all the seeds are out, the crude seed material is purified by screening through a fine mesh.

There is also another hyssop that thrives in savannas, purple hyssop (Agastache scrophulariaefolia). We were given a small amount of seed from a nearby site and introduced this also about 10 years ago. For many years we had just a few plants, but in recent years it has spread well through the savannas. In fact, we had one site this year in Unit 13 that had both species flourishing side by side.

Once they set seeds, these two species look very much alike, and one has to pay special attention to the leaves, stem, and shape of the seed head to determine which is which.