Upon my arrival at Broadwell Hill Learning Center one thing that was brought to my attention was helping to identify a particular invasive species of common reed, Phragmites australis to be specific. More specifically how to differentiate the invasive Phragmites australis from the native subspecies Phragmites americanus. Identification is not easy early in the season but it looks like there a few distinguishing traits that can help us.
One particular sign to spot australis will be in the root clusters. They will be difficult to break apart, sheaths of leaves will be tightly wrapped to the stem base and require good effort to separate. Even further down the roots will all tie together to form and huge knot of root clusters. Large clusters will root down three to four feet deep.
After reviewing the links below and searching the web I do not suspect australis is in the Sacred Pool. However, further verification will need to be done later in the season. Australis will grow to 15ft. high, significantly taller then the other species. It will also take on a dark or blue-green color later in the season as plants mature. This particular subspecies will remain this color well into the later seasons when it begins to flower. It then will die off at the surface to make room for new growth the next year. The roots will continue to grow into thick clusters up to 3ft. deep making this species a nuisance to remove
Most sites have suggested contacting professionals to distinguish between the species americanus and australis. Until recently not much information was being spread about the Native species, leading to Phragmites americanus being killed off mistakingly. The links below require more detailed information on the two species.
Note that there are two different North American species, australis and berlandieri. Berlandieri is more prominent in South and coastal Florida.
See link for more info: https://www.minnesotawildflowers.info/grass-sedge-rush/american-common-reed
Phragmites australis Plant Profile: https://plants.usda.gov/core/profile?symbol=PHAU7
Phragmites Field Guide Distinguishing Native and Exotic Forms of the Common Reed: https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/idpmctn11494.pdf