What is "hedge hyssop"

Hedge \Hedge\, n. [OE. hegge, AS. hecg; akin to haga an inclosure, E. haw, AS. hege hedge, E. haybote, D. hegge, OHG. hegga, G. hecke. [root]12. See Haw a hedge.] A thicket of bushes, usually thorn bushes; especially, such a thicket planted as a fence between any two portions of land; and also any sort of shrubbery, as evergreens, planted in a line or as a fence; particularly, such a thicket planted round a field to fence it, or in rows to separate the parts of a garden. The roughest berry on the rudest hedge. --Shak. Through the verdant maze Of sweetbrier hedges I pursue my walk. --Thomson. Note: Hedge, when used adjectively or in composition, often means rustic, outlandish, illiterate, poor, or mean; as, hedge priest; hedgeborn, etc. Hedge bells, Hedge bindweed (Bot.), a climbing plant related to the morning-glory ( Convolvulus sepium). Hedge bill, a long-handled billhook. Hedge garlic (Bot.), a plant of the genus Alliaria. See Garlic mustard, under Garlic. Hedge hyssop (Bot.), a bitter herb of the genus Gratiola, the leaves of which are emetic and purgative. Hedge marriage, a secret or clandestine marriage, especially one performed by a hedge priest. [Eng.] Hedge mustard (Bot.), a plant of the genus Sisymbrium, belonging to the Mustard family. Hedge nettle (Bot.), an herb, or under shrub, of the genus Stachys, belonging to the Mint family. It has a nettlelike appearance, though quite harmless. Hedge note.

1. The note of a hedge bird.

2. Low, contemptible writing. [Obs.]
   --Dryden.

   Hedge priest, a poor, illiterate priest.
   --Shak.

   Hedge school, an open-air school in the shelter of a hedge, in Ireland; a school for rustics.

   Hedge sparrow (Zo["o]l.), a European warbler ( Accentor modularis) which frequents hedges. Its color is reddish brown, and ash; the wing coverts are tipped with white. Called also chanter, hedge warbler, dunnock, and doney.

   Hedge writer, an insignificant writer, or a writer of low, scurrilous stuff. [Obs.]
   --Swift.

   To breast up a hedge. See under Breast.

   To hang in the hedge, to be at a standstill. ``While the business of money hangs in the hedge.''
   --Pepys.