Strategies for Identifying Agastache Species and Other Native Plants
I don’t usually get fussy or wonky about different native plant species but when I learned the range for the most common hyssop called blue giant or anise hyssop (Agastache foeniculum) doesn’t include Georgia, I tried to identify what species were growing in my yard. Anise hyssop is a popular edible herb known as a pollinator magnet, so I didn’t want to get rid of it if I was growing it. I just wanted to see if I had other species best suited for Georgia. Problem is, figuring out the differences between the native plant species as a non-expert can be a challenge. There are hundreds of native plants in my yard and my original goal to have a label for each is becoming comical as the plant communities mingle and become more “rewilded”!
The agastache mystery involved several native plant touchpoints and included identifying native plant species, the most durable plant labels, the nursery trade, cultivars, the value of herbs, and the issue of native plants outside their range. I’ll try to add a little perspective on these points as I explain how I problem solved identifying my agastache mystery. (Click on highlighted words for links with more details)
I use a range of strategies to identify native plant species and they include:
Making sure to put labels by each plant which is easier said than done. Critters, weather and other plants sometimes move labels but in general I can still find most of them. The most reliable way to label plants is to put waterproof printable labels on metal plant labels. This can initially be an expensive purchase, but the labels last for years.
Plant ID apps help immensely. My favorite is PictureThis which is correct most of the time except when it comes to native grasses and sedges. Other popular apps to try are Seek by iNaturalist, Pl@ntNet, and Google Lens.
Native plant groups have members who know their plant Latin and can tell you if the leaf shape is lanceolate, aristate, cordate, or obovate! Their willingness to share their plant identification skills is invaluable to those of us who are still learning. In Georgia, my favorite Facebook resource is Georgia Native Wildflowers and Plants.
My native plant friends are also immensely helpful when we do mini habitat tours in each other’s yards. Building friendships and sharing information with others is one of the most satisfying ways to learn about plant differences. For me joining the Intown Atlanta chapter of the Georgia Native Plant Society has also been a way to find others who can talk plants and are interested in protecting nature using native plants.
Visiting local resources such as public native plant gardens, natural areas, or native plant habitat tours helps me learn more so I can feel more confident with identification. Learning about a native fern on a recent guided nature walk in the Fernbank Forest helped me in identify a fern growing in my yard. When I visited the gorgeous prairie inspired Entrance Gardens at the Atlanta History Center the large patches of labeled downy skullcap (Scutellaria incana) helped me confirm that this is the same species I have.
Taking photos of labels and plants at local native plant nurseries can be used to compare plants in question. This is also a great excuse to find even more native plants to add to the yard!
One slightly over the top strategy I use when I get confused by native plant species is to winter sow new plants of the plant species in question. This approach takes a bit of time and planning.
I’ve also bought species of a plant in question at native plant nurseries to make sure I know what I have! A couple years ago I had a big plan to grow 17 native goldenrod (solildago) species in my yard, but keeping track of them was ridiculously impossible. Some species look too similar, and the rhizomatous ones “move” which makes it even more difficult! I have since bought a few of goldenrod species to use as a reference for plants already growing in my yard and can now identify a handful with certainty.
Taking classes in person or online and reading guidebooks about native plants is a way to be more confident identifying the subtle differences in plants. I’m not great at using field guides but people who are good at identification swear by them. Native plant societies including the Georgia Native Plant Society often have useful links to help identify native plant species including plant guides, state specific sites, blogs, and organizations.
Targeted internet searches about a plant can help narrow down identification. This works if there is a clear difference, but some native plants like helianthus and aster have so many similar species that I find a more hands-on identification approach helpful.
Using some of the approaches above and a little detective work helped me figure out what species of agastache are growing in my yard.
Of the 30 species of agastache only a handful are native to North America. Traditional nurseries are filled with cultivars of non-native Agastache rugosa or Korean mint which can self-seed more vigorously and displace native agastache. There are also many cultivars of native agastache popular in the nursery trade and have names like Agastache ‘blue fortune’ or Agastache ‘premium blue’. The habitat value of cultivars is a comple situation so I err on the side of shopping at native plant nurseries and buying the straight species whenever possible. It is unlikely I would have any agastache cultivars which helped narrow down my search to a few natives.
Labels from native plant nurseries can get confusing if the label doesn’t have a Latin name on it and it is simply called "giant hyssop". This means at least in Georgia the hyssop most likely sold at a native plant nursery is either blue giant hyssop (A. foeniculum), purple giant hyssop (A. scrophulariifolia), or yellow giant hyssop (A. nepetoides). All three species have similar flower spikes covered in tiny blooms and are visited by a host of pollinators including bumblebees, butterflies and hummingbirds. Goldfinches love their seeds heads. Their size, color, and growing conditions vary,
1 - Agastache foeniculum is often called anise Hyssop, blue giant hyssop or lavender hyssop and grows up to 4 feet tall in sunny areas. The flower spikes are covered with tiny bloom that range from light lavender to dark violet. The undersides of the leaves are white or light grey. Anise hyssop will bloom the first year from seed and self-seeds if happy where it is growing. It is not native to Georgia, but it can be grown as an edible herb with the added benefit of supporting pollinators.
2 - Agastache scrophulariifolia is also called purple giant hyssop, grows about 6 feet tall and has white to pale purple flowers. It doesn’t compete well with other plants so needs its own space. Purple giant hyssop has been historically found around the Piedmont region. It is listed as threatened or endangered in multiple states including Georgia where it is currently ranked S1 by the Georgia Department of Natural Resources, meaning it is critically imperiled.
3- Agastache nepetoides or yellow giant hyssop can reach up to 8 feet and the lower leaves can be plate size! The color is not a bright yellow but a subtle greenish yellow to creamy yellowish white. Yellow giant hyssop does fine in our hot, humid Atlanta summers if it is in slightly moist, partially sunny areas. It dies out in dry, sunny areas. It is also not as fragrant as the other hyssops. Agastache nepetoides is also ranked S1 by the Georgia Department of Natural Resources, indicating that it is critically imperiled in the state.
I think I’ve solved my agastache mystery. One of the agastache species growing in numerous parts of my yard is Agastache foeniculum. This is the most common hyssop found in Georgia yards because it’s used as an herb. Edibles are in a different category than non-natives so I plant edible herbs and let them go to seed as a nectar and food source for wildlife. Most of me agastache plants are also in the 3-5 foot range and my PictureThis app confidently identified them as A. foeniculum.
I’m also fairly certain I also have Agastache schrophulariifolia and not Agastache nepatoides based on the size, my PictureThis app, and the color of the flowers compared to targeted internet searches. I also looked at the two species of Agastache sold at my local native plant nursery. My sleuthing conclusions were confirmed when I crawled around on the ground under where two species of agastache are growing and was able to find a half buried label!
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