Solidago flexicaulis is leafing out in the yard of the Friends Center on Cherry Street, just west of 15th Street.
Witch hazel is blooming at 10th and Locust, and winter aconite is blooming right next to Vernon Park (in Germantown).
Winter aconite has been growing at Bartram’s Garden since at least the 19th century: https://growinghistory.wordpress.com/2012/02/24/a-visit-to-bartrams-garden-with-the-philadelphia-botanical-club/
Philadelphus inodorus grows along the Wissahickon trail just a bit downstream from the entrance to Forbidden Drive.
It has 3 flowers per cyme (and some single flowers), hairs in the underside leaf vein axils, and it is arching (and definitely not upright).
Taylor’s Flora of the Vicinity of New York (1915), which includes Philadelphia, has Philadelphus inodorus as not native to Philadelphia:
And Porter’s Flora of Pennsylvania (1903) has it as naturalized in Pennsylvania:
In the Flora of Bucks County (Benner; 1932), P. inodorus is noted as “Escaped from cultivation and established along steep bank, New Hope”; and in the Flora of Lancaster County (Small and Carter; 1913), P. inodorus is noted as “Nat[ive] of the s. U. S.”.
It is not in Barton (1818):
In the New Britton and Brown Illustrated Flora (Gleason; 1952), P. inodorus habitat and range are noted as: “Stream banks and moist hillsides or cliffs, chiefly in the mountains, e. Pa. ; N. C and Tenn. to Ga. and Ala. ; frequently cultivated and occasionally escaped northward.”
Along the Wissahickon trail, upstream from the Henry Avenue Bridge, Solidago flexicaulis (with axillary inflorescences and wide leaves) is common, right by the trail, underneath the trees, on the way to Forbidden Drive.
Along the trail above, on the other side of the creek and up the hill in the woods, where it’s a bit drier, but still shady, Solidago caesia (with axillary inflorescences and narrow leaves) is common.
On the trail leading from Blue Stone Bridge, and leading along downstream (and up in the woods on the hill), both Solidago caesia and Solidago flexicaulis can be found.
In open areas, along the stream, Solidago gigantea (with smooth, glaucous stems) is very common; Solidago rugosa (with scabrous leaves) is also there. Underneath the Henry Avenue Bridge, there’s a thick stand of Solidago gigantea, and right next to that, there is an individual of Solidago rugosa.
Up on the hillsides, Solidago rugosa is the more common one in open areas.
Underneath a good sized (>2.5′ dbh) tulip poplar, just upstream from “Help Locator #125”, on the sunnier side of the tree there’s a robust stand of Solidago gigantea, and on the shadier side of the tree, there’s a robust stand of Solidago flexicaulis.
And so, overall, it appears that in this area, shady places that are moist have Solidago flexicaulis, shady areas that are drier have Solidago caesia, open areas that are moist have Solidago gigantea, and open areas that are drier have Solidago rugosa – and there is co-occurrence, in certain habitats.
Along the trail that goes from the white pines of Hermit Lane and passes under the Henry Avenue Bridge (and then goes onwards to Lovers Leap), there are no goldenrods along the trail, until after you pass beyond the bridge above.
NB: Eurybia divaricata (white flowers) and Eurybia macrophylla (lavender flowers) are both in flower – macrophylla appears to be at lower elevations than divaricata.
An empress tree is flowering at the Allegheny train station.
There’s a ginkgo tree, over 3″ dbh, growing just a bit south of the white pines of Hermit Lane, in the wooded area next to the Hermitage.
Xanthium strumarium (with cordate leaf bases) is in fruit along the Wissahickon trail, downstream from the Henry Avenue Bridge, and Solidago caesia (with lanceolate leaves and sometimes-blue-and-glaucous stems, and axillary inflorescences) is flowering along the trails up above in the woods – Solidago flexicaulis (with wide basal leaves, and axillary inflorescences) is flowering along the Wissahickon trail, just a bit downstream from Forbidden Drive (under the trees along the trail).