This species is bivoltine and induces morphologically different bud galls in spring (April–May) and summer (August–September), which are very similar on all three host plants. ... White chambers that are similar to those in the spring galls appear in the gall around mid July ... and each chamber contains a single larva that is found deep in the chamber, facing downwards. Each chamber is surrounded by a group of very short and narrow leaves, which in turn are surrounded by longer and wider leaves to form a distinct subunit within the gall. Usually at least 2–5 subunits are clumped together at the shoot apex to form a conspicuous rosette that is 3–5 cm in diameter. ... The rosette gall of R. capitata ... is superficially similar but does not contain distinct subunits and appears flatter than galls of R. solidaginis.

[Rhopalomyia] solidaginis. Widespread eastern Nearctic. Solidago altissima; S. canadensis, S. rugosa (Asteraceae)

Cecidomyia solidaginis Loew 1862: 194. USA: New York, West Dryden; NT, des. Dorchin et al. 2009: 30; ♂; USNM. Ref.: Dorchin et al. 2009 (redescr.).
Rhopalomyia albipennis Felt 1908b: 364. USA: New York, Albany; ST; ♂,♀; NYSM.
Rhopalomyia carolina Felt 1908b: 363. USA: North Carolina, Asheville; HT; ♀; NYSM.

...from an apical, leafy cluster gall on Solidago canadensis [note: Plakidas does not appear to distinguish S. canadensis from its close relatives]

Bud or flower gall...
Galls made up of bud leaves, often as rosette on foreshortened stem...
Rosette galls made up of 25 to hundreds of leaves...
Gall with numerous, imbricated leaves, the inner leaves narrow; on S. canadensis and close relatives...Rhopalomyia sp.

This gall is common Solidago canadensis. Although superficially similar exteriorly to one on S. juncea, the two are structurally different, and an asphondylia is responsible for the one on S. juncea...

[note: Gagné states elsewhere that he uses "S. canadensis" in a very wide sense, encompassing at least S. altissima and S. gigantea.]