Umbel:- An inflorescence in which all the branches (rays) arise from the same point, like the spokes of an umbrella.
Umbilicate:- Navel-like, with a small central hollow or depression
Umbonate:- ± round and bearing a small boss or ' elevation in the centre.
Unarmed:-  Without spines or prickles.
Uncinate:- Hooked at the apex or tip
Undulate:- With a wavy margin curving up and down
Unguiculate:- Clawed, narrowed into a stem-like base.
Unilateral:- One-sided, relating to, occurring on, or affecting only one side of an organ or structure.
Unilocular:- Having a single compartment in the ovary or fruit, as in a melon
Unisexual:- Having only one sex in the flower or plant, either male or female.
Untoothed:- Margins of leaves or petals that are not toothed (en­tire).
Urceolate:- Urn-shaped
Utricle:- Bladder-like structure

A subdivision of a species or subspecies, often differing in a single character; often growing with or close to the typical plant.
Valvate:- When similar parts of the plant meet exactly without overlapping.  meet exactly without overlapping.
Valve:- One of the segments into which a capsule or pod naturally splits on maturity.
Vein:- A strand, strengthening or conducting tissue running through leaves, petals etc.
Velutinous:- Velvety, with very short dense hair or sales, soft to the touch.
Velutinous-tomentose:- Covered with short, dense, matted velvety hairs.
Vermiculate:- With wavy lines or markings resembling the form or tracks of a worm.
Ventricose:- 1) fat, swollen; 2) swollen or bulging on one side (usually near the middle)
Warty, with little excrescences or bumps
A condensed cyme produced at the leaf-nodes and often forming distinctive whorls of flowers up the stem - as in many members of the Labiatae.
Verticulate:- Arranged in whorls
Vesicular:- Covered with little blisters 2) bladder-like
Villose, villous:- Covered with long, shaggy hairs.
Villous-plumose:- Covered with long, shaggy, softly feathery hairs.
Villious-lanate:- Covered with long, shaggy, dense curly interwoven matted woolly hairs.
Resin canals.

Wedge-shaped:- Narrow at the point of attachment, but gradually widening and with straight sides - as in a wedge.
Whorl:- More than two organs arising at the same point on the stem - leaves or flowers.
Wing:- The lateral petals in a pea flower. many orchids etc.

Zygomorphic:- An irregular flower having only one plane of sym­metry