The initial idioms of the letter H

Holarrhena	Holarrhena antidysenterica
Holarrhena pubescens	Holbein
Holbein the Elder	Holbein the Younger
Holbrookia	Holcus
Holcus lanatus	Holcus mollis
hold	hold back
hold close	hold dear
hold down	hold fast
hold firm	hold forth
hold in	hold off
hold on	hold one's own
hold open	hold out
hold over	hold still for
hold sway	hold the line
hold tight	hold up