GOLDENROD

It's Flower Friday and this plant is announcing itself all over the place around here.  It's commonly called Goldenrod (Solidago sp.) and this is one of ten members of the Genus I know about.  Not certain which one it is as I have yet to Key it out.  If you absolutely need to know which one, press me and I'll get around to doing it.
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This plant is commonly parasitized by a small wasp. Technically, it's not really parasitism as the host is always harmed in that relationship but seldom killed by a true parasite.  This small wasp, a gall wasp, lays an egg in the stem of the plant.  It does not harm the host plant at all...but the egg presence must be irritating because the stem grows a warty structure around them (a gall) to seal off the egg, in effect, from the rest of the plant. Your body does the same thing after certain viruses enter your skin...and you grow a wart around the virus to separate it from the rest of the body.
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This gall will grow to about the size of a small ping pong ball, the egg will mature into a small grub that then eats the soft interior gall material during the growing season...this does no harm to the host plant.  Eventually, the grub will enter the pupa stage within the gall and spend the winter there hidden inside the gall and insulated from the freezing winter temperatures outside.
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In the Spring time, the pupa will hatch into an adult gall wasp which will eat its way to the edge of the gall and escape through the hole at the end of the tunnel to start the life cycle over again.
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Ice fishermen, myself included, "harvest" these galls from the stems of last year's growth and take them along to the frozen lake.  A quick knife cut through the gall reveals the pea-sized grub which can be used as bait for panfish.  Check out these two links for photos and greater explanation:

https://www.fllt.org/inside-the-goldenrod-gall/

goldenrod wasp gall opened
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Best in Large.