| Name | Structure/ Category | Description |
|---|---|---|
| Heterosporous | characterized by the production of asexual spores of more than one kind | |
| Hip | [Fruits] {type} | An aggregation of achenes surrounded by an urn-shaped, more or less fleshy floral cup or hypanthium, as in roses (Rosa). |
| Hirsute | [Buds, Leaf lower surface, Leaf upper surface, Petioles, Phyllaries, Rachises, Sepals, Young twigs] {pubescence type} | With coarse, stiff hairs. |
| Hispid | [Buds, Leaf lower surface, Leaf upper surface, Phyllaries, Sepals, Young twigs] {pubescence type} | With stiff, bristly, usually stout-based hairs. |
| Hollow | [Pith] {type} | With an uninterrupted central cavity, the pith lacking or disintegrating prior to maturity. |
| Homosporous | characterized by the production by various plants (as the club mosses and horsetails) of asexual spores of only one kind | |
| Hoods | Erect columnar structures on the upper part of a Milkweed flower in the Asclepiadaceae. | |
| Horn | A slender horn-like structure inside or adjacent to the hood of a Milkweed flower in the Asclepiadaceae. The horns are straight or curved, and usually shorter than the hoods. The flowers of some Milkweed species lack horns. | |
| Host | a living animal or plant affording subsistence or lodgment to a parasite | |
| Husk | the outer covering of a kernel or seed esp. when dry and membranous |
