The Solidago aka Goldenrod Project's Journal

an iNat project on Euthamias - (the other goldenrods)

https://www.inaturalist.org/projects/systematic-evaluation-of-euthamia

an interactive key to solidagos from Canada and the US from the Shirley C. Tucker Herbarium
http://www.herbarium.lsu.edu/keys/solidago/solidago.html

Phylogenetics of Euthamia (Asteraceae: Astereae) and Asteromyia euthamiae
(Cecidomyiidae: Alycaulini)
Marisa Blake Szubryt
https://opensiuc.lib.siu.edu/uhp_theses/436/

When learning to identify a group of plants, it can be helpful to figure out how to tell when it is definitely not the thing you are trying to learn to identify. So here's some things to help you decide if a plant is solidago or not solidago...

If the flowers are any color other than yellow or white, it is not a solidago. Most solidagos have bright yellow flowers - a few species are white. If the flowers are red, blue, purple or green - not a solidago.

If the plant has a persistent woody stem like a tree or a shrub, it is not a solidago. All solidagos are herbaceous- their stems do not have a woody core. When a herbaceous plant emerges from dormancy, it grows new stems from buds at ground level. No new growth begins from buds above ground on the previous years stems.

If the plant is taller than 3 meters, it probably isn't a solidago. The tallest species can grow to around 2.5 meters but most species are much shorter.

If the plant does not have compound flowers, it is not a solidago. Each solidago flower is made up of tiny individual florets packed together-a ring of pistillate ray florets surrounding a group of perfect disc florets, each capable of making a single seed. If the compound flower is all ray florets or all disc florets then it is not a solidago.

Compound flowers are surrounded by a ring of specialized leaves known as phyllaries (https://en.wikipedia.org/wiki/Phyllary). Solidagos have two to four rings of overlapping phyllaries, each with a single translucent central vein.

Solidagos are native to North and South America, the Azores, Europe and Asia. The highest species diversity is found in the solidagos growing in North America.

Diversions
Silicon Valley: Season 4 Episode 4
https://www.youtube.com/watch?v=pqTntG1RXSY

Identification of goldenrods can be IS challenging. One expert wrote, "It's only taken me about 50 years to get to the point where I think I might final know something about goldenrods. In another 50 years I should have them mastered."

Here's a list of helpful things to observe when you find an unfamiliar plant that you think might be a goldenrod...

1. Location

   • if the plant is being cultivated, remember to check the captive/cultivated checkbox when uploading, or put the thumbs down beside 'Organism is wild' on the observation page on the web.
   • check that your accuracy circle on the observation is not grandiose.

2. Habitat

   • include a 'wide shot' - an image that includes the plant you are observing and the area surrounding. Others can see if the site is sunny or shaded and from the other plants nearby can make assumptions about the soil and moisture conditions.
   • add a note about the soil and moisture conditions in the observation description. Soil might be rock, gravel, sand, clay, humus. Moisture might be dry, moist, wet.

3. Flower

   • an image showing the complete flower head or inflorescence from the side showing the branching pattern.
   • an image showing the arrangement of the individual smaller flower heads or florets on the branches of the inflorescence.
   • a 'close-up' image of the ring of specialized tiny leaves or bracts on the outside of the florets. Identifiers are looking for very small hairs or the patterns of the veins or the presence of tiny lumps or glands so zoom in as close as your equipment will allow.
   • a view of a single floret from the top showing any patterns in the arrangement of the tiny flowers that make up each floret.

4. Stem

   • an image showing the whole plant from the soil to the top of the inflorescence. This will also show the overall size of the plant and its growth habit.
   • 'close-up' images of the flowering stem at the base of the plant, midway up the stem and just under the inflorescence. Identifiers are looking for changes in the texture and colour of the stem surface

5. Leaves

   Solidago plants often have different leaf shapes at the base of the plant, midway up the stem and just under the inflorescence. For each leaf shape include

   • the leaf from above showing the full length from stem to tip;
   • a 'close-up' of the underside of the leaf showing any hairs or glands;
   • the place where the leaf joins the stem showing the length of the leaf stem or petiole and any small leaves or bracts.

6. Other organisms

   Add each organism observed on the plant to its own individual observation. Use the observation group field to link them all the observations together. Some of the organisms you will observe are specialized to live in a single species of Solidago. and their presence helps contribute to identifying the plant.

   • any organisms clinging or feeding in the inflorescence. Bees, butterflies and hover-flies visit the flowers for nectar and pollen. Spiders and ambush bugs hide in the flowers ready to spring on the unwary.
   • any organisms feeding on the stem or leaves. Caterpillars, bugs and beetles may be found on the stems or under the leaves. Leaf miners live in the interior of a leaf chewing distinctive patterns as they mature. Gall makers modify the tissues of the plant to create unusual structures in which they hide.

It can take a bit of effort to gather and upload all this information. As the observer, you decide how much is enough. Some Solidago species only require a clear location, and a good image of the inflorescence and the overall plant for a secure id. Others are puzzles even with all the images listed above. Adding the extra effort when in an area with few RG observations or when you have time to spare is much appreciated.

Solidago taxonomy is still being explored. Each new understanding creates a little ripple of reclassification to the existing iNat data. These ripples in turn help to create a better understanding of Solidago in the landscape.

More Resources

• Goldenrods at Astereae Lab - John C. Semple https://uwaterloo.ca/astereae-lab/research/goldenrods
• Solidago in Plants of the World Online http://plantsoftheworldonline.org/taxon/urn:lsid:ipni.org:names:60436299-2
• Solidago in the Flora of North America http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=130659
• Insect Galls on Goldenrod - Daniel McClosky https://www.inaturalist.org/journal/ddennism/28052-goldenrod-galls