GR translation: be he always in flower

[Mike Jing]

V580.3-13, P590.1-11   “You have the two choices,” Jamf cried, his last
lecture of the year: outside were the flowery strokings of wind, girls in
pale-colored dresses, oceans of beer, male choruses intensely, movingly
lifted as they sang Semper sit in flores/ Semper sit in flo-ho-res . . .
“stay behind with carbon and hydrogen, take your lunch-bucket in to the
works every morning with the faceless droves who can’t wait to get in out
of the sunlight—or move beyond. Silicon, boron, phosphorus—these can
replace carbon, and can bond to nitrogen instead of hydrogen—” a few
snickers here, not unanticipated by the playful old pedagogue, be he always
in flower: his involvement in getting Weimar to subsidize the IG’s
Stickstoff Syndikat was well known—

What does the inversion of subject and verb in "be he always in flower"
indicate here?