Geum macrophyllum is an attractive, late spring- to early summer-flowering species that is listed as endangered in the State of New York. There are two varieties, a widely distributed var. macrophyllum (with shallowly lobed leaves), and a more western var. perincisum (with more deeply incised leaves). The only variety that occurs in the northeast, including NY, is var. macrophyllum.
If you are an iNaturalist user you will find that observations of Geum macrophyllum extend well south of the range of this species documented by other sources. The BONAP (www.bonap.org) range map, which is based primarily on specimen data, indicates that in the Northeast G. macrophyllum does not occur south of WI, MI, NY, VT, or NH. A few counties shown on the map for NY are also probably in error. For example, the specimens that form the basis for the Chemung County records are G. laciniatum that were probably misidentified based on large basal leaves produced late in the season…more on that later.
On the iNaturalist map the states and provinces shaded in green represent areas where observations are “research grade”, that is ones where there is consensus among users as to the identity of plants pictured in the observation. Notice all the red dots south of the aforementioned states are in need of ID. These all contain photos of plants without flowers or fruit and are typically of basal leaves taken late in the season and are most certainly not Geum macrophyllum.
Based on the first map it is evident that Geum macrophyllum is a primarily northern species that is seemingly intolerant of high summer temperatures. In growing this species from seed I have managed to get plants to flower after a year but they get smaller and smaller in subsequent years and will likely not survive long term. They seem to struggle the most during the heat of summer. In the southern part of its range it is mostly confined to cool microclimates and is unlikely to be found in open areas as is G. aleppicum. The southernmost location in New York is the Peekamoose Valley where cold headwater streams from the Catskill High Peaks drain into Rondout Creek. On one visit in the middle of July the temperature was in the mid 80’s entering the valley but where G. macrophyllum was growing was closer to 70°F!
Geum macrophyllum is probably the most frequently misidentified species of the genus in the northeast and the specific epithet and common name likely play a role in this. The basal leaves are actually not all that large compared to other species most of the year. The name derives from the large terminal leaflet that is indeed much larger than the lateral leaflets (a shape known as lyrate) and this leaf shape tends to be consistent throughout the growing season. Other Geum spp. tend to produce more pinnately lobed or lacerate basal leaves early in the season, however the basal leaves produced from around the time of flowering through the remainder of the growing season are frequently much enlarged and can look quite similar to and exceed the size of the basal leaves of G. macrophyllum. These other species include G. aleppicum, G. canadense, G. urbanum, G. laciniatum, and G. vernum. The latter, because of its early bloom time, actually starts producing large basal leaves as early as late May!
The fruit of several species are also frequently confused with those of G. macrophyllum. The main ones are G. aleppicum and G. laciniatum because they are equally large, while other Geum spp. tend to have smaller fruit or the fruit that looks quite different.
Two characteristics can be used to separate the fruit of G. macrophyllum from the other large-fruited species. One is the presence of stipitate glands on the persistent style of the achene (sometimes called the ‘beak’).
Geum aleppicum has hairs on the styles but they are eglandular. Geum laciniatum sometimes has eglandular hairs (var. trichocarpa) but they are mostly confined to the body of the achene and the very base of the style.
A few other species can have stipitate glands on the fruit. These include G. rivale and G. vernum, however both of these species have the head of achenes elevated on a stipe (short stem). Another species that can sometimes have glands is Geum canadense, though this species and G. vernum have much fewer achenes and thus the head is significantly smaller.
Another unique characteristic of the fruit (and also the flowers) of G. macrophyllum is the lack of epicalyx bractlets. These are small green structures that alternate with the sepals. Occasionally an individual flower of G. macrophyllum can have a few, very poorly developed bracts but I have never seen them well-developed as in other species. The only other Geum species in New York that lacks epicalyx bracts is G. vernum but it has much smaller achenes that are fewer in number and the head of achenes, as previously mentioned, is elevated on a stipe.
Finally, the shape of the middle stem leaves of G. macrophyllum var. macrophyllum can be useful in separating this species from other similar yellow-flowered species, particularly G. aleppicum. They tend to have three rounded, relatively shallow lobes. The variety of G. macrophyllum with more deeply incised stem leaves (var. perincisum), which might be confused with G. aleppicum, is not found within our range.
