GR translation: hair smocks

[Michael Bailey]

Mike Jing wrote:

V5.20-26, P5.35-41   Bloat is one of the co-tenants of the place, a
maisonette erected last century, not far from the Chelsea Embankment, by
Corydon Throsp, an acquaintance of the Rossettis’ who wore hair smocks and
liked to cultivate pharmaceutical plants up on the roof (a tradition young
Osbie Feel has lately revived), a few of them hardy enough to survive fogs
and frosts, but most returning, as fragments of peculiar alkaloids, to
rooftop earth, . . .


What's a "hair smock" exactly? Is it a smock you wear when you are having a
haircut?


That’s all I could find under “rosettis pre-Raphaelite hair smock” and
similar searches.

I was really hoping for something outrè, like smocks made out of hair,
but didn’t find anything like that.