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 more rewilded my yard becomes the harder it is to identify all the plant species in it.

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)

Sharing my process for identifying the two species of agastache in my yard gives me the opportunity to share my identification strategies, favorite plant labels, the challenges of finding native plants at traditional nurseries, and the place herbs might have in a naturescaped yard.

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.

Printed waterproof labels on "professional" metal plant labels are the best way I've found to ensure I can identify plants. My biggest challenge with them is making new labels when I add new plants!

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.

PictureThis is my favorite app for identifying plants. No app is perfect, but this seems to be able to tell most of the species apart. For fun I tried it on a handful of solidago species and it didn't let me down!

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.

When the rest of us describe leaves of wild ginger (asarum canadensis) as heartleaf, plant nerds might describe them as cordate.

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.

Since becoming involved in the Intown Atlanta chapter of the Georgia Native Plant Society I’ve met other people who I can geek out on native plants with. (photo of Alex and Grace who are on the board of the Atlanta Intown GNPS)

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.

When I visited the Atlanta History Center I was able to confirm the downy scullcap (scutellaria incana) growing in multiple garden beds was the same species as an unidentified one I have in my yard. (I was even more excited to find threatened American bumblebees (Bombus pensylvanicus) on them!)

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!

Sometimes it helps if I take snapshots at local native plant nurseries of plant species I routinely struggle to easily identify. Solidago species continue to vex me!

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.

This January I winter sowed Cirsium discolor (field thistle) because last year I confused this with Cirsium altissimum (tall thistle) and it didn't fair well in the moist area that tall thistle like but pasture thistle doesn't.

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.

I've been known to buy a few different species of a plant to confirm what I already have growing...again, goldenrod is not my friend when it comes to plant ID! (This solidago caesia was for sale at North Georgia Native Plant Nursery)

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.

There are so many amazing field guides to help identify plants. Beech Hollow native plant nursery in Atlanta has a nice selection.

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.

Sometimes internet searches can help identify different native plant species, particularly if you've narrowed down the species and you look at images, I wouldn't begin to try this with plants with many similar species such as one with small daisy-like flowers. This plant just started blooming this week and could be a false aster (boltonia asteroides), panicled aster (symphyotrichum lanceolatum), or something else! (I think based on the time it's blooming it's a false aster...but welcome other IDs)

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.

I can easily guess the two species of agastache growing in my yard are native.

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,

The agastache is popular with the goldfinches in my yard. This cute couple visits together at dinnertime!

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.

Blue giant hyssop (agastache foeniculum) may not naturally grow in my ecoregion, but it's a popular pollinator friendly native herb plant!

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.

The Purple giant hyssop (agastache scrophulariifollia) pictured is critically imperiled and the American bumblebee buzzing around it is threatened. I would encourage anyone who is restoring nature in their yard to seek out the agastache scrophulariifolia at native plant nurseries and add it to the landscape if it naturally would grow where you live. Doing this may help both species. The American bumblebees I see in my yard seem to prefer the purple giant hyssop.

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.

The silver-spotted skipper butterfly is just one of many pollinators attracted to anise hyssop! There's no reason not to grow this if you live in Georgia, just add the other two species of critically imperiled agastache listed here to your yard to help nurture nature where you live!

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!

I unearthed this tag under the patch of native plants where the two agastache species were growing. Now that I know this is a critically imperiled species in Georgia, I'm going to add as many plants of it as possible to my yard!

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