Late summer here in Deering and fields and roadsides have been yellow for a while now. First came the black-eyed Susans, now goldenrods dominate. They’re the ones that form great swathes of yellow in sunny meadows and along roadsides.
Small digression . . .
Solidago, a name derived from Medieval Latin, Soldago (to make whole), was applied to this group of plants because of their medicinal value. There are lots of links for goldenrods and Solidago, on the WEB.
Goldenrods are a tricky proposition for anybody who wants to identify species. However, some species can be identified readily from a distance of 2 meters based on their form and/or flower color.
For example . . .
The flowers of Solidago bicolor, which are just now (end of August) opening, are white with maybe just a touch of yellow. You might not think this one was a ‘goldenrod,’ but it is. This species is common here along roadsides and other dry sites in full sun.
Another distinctive goldenrod is no longer classified in the genus Solidago. Euthamnia graminifolia, which you will still find in wildflower guides under Solidago, really does not look like your average goldenrod. Its two common names reflect the differences. The very narrow, pointy leaves suggest leaves of grass, hence the species name graminifolia. The second distinctive characteristic of this species is the fact that the heads of flowers all form at more or less the same level (unlike other goldenrods where ‘flowers’ (really, heads of flowers or ‘racemes’) can look like fountains – – or star burst fireworks!). Thus the common name ‘flat-top-goldenrod.’
But, something else distinguishes flat-top-grass-leaved-goldenrod.
It’s an insect. A kind of a fly known as a ‘gall midge.’ Euthamnia graminifolia is the one and only host for the gall midge Asteromyia euthamniae. I have not found much information about this gall midge on line, but infected plants are pretty common here in Deering. Typically the larva of a gall midge burrows into the leaf’ and this elicits a response from the plant, which results in the formation of this characteristic gall. The gall is first bright yellow but becomes the tarry black shown in these pictures. After pupation an adult emerges to repeat the cycle. The Euthamnia gall midge, a nondescript fly, can repeat the cycle two or more times from spring through fall. Not all, but many grass-leaved goldenrod plants are affected and the species is common in Deering.
Euthamnina graminifolia is a native of North America, where it is widely distributed. The species typically occurs in damp places, but it can also be found under dry conditions along roadsides and in fields. This is one species that has been spread to Europe from North America. The species is commercially avilable.