U

Ultraviolet [ Climatology - Physics ]

Un- [ Prefix ]

Unbranched [ Botany ]

Uncinate [ Botany ]

Underground [ Botany ]

Undergrowth [ Botany - Ecology ]

Underpotting [ Horticulture ]

Understock [ Horticulture ]

Understorey [ Botany - Ecology ]

Underwatering [ Horticulture ]

Undescribed [ Taxonomy ]

Undeveloped [ Biology - Botany ]

Undifferentiated [ Biology ]

Undulate [ Botany ]

Unfertile [ Botany ]

Unfruitful  [ Botany ]

Unamed [ Taxonomy ]

Uni- [ Prefix ]

Unicellular [ Biology ]

Unifoliate - Unifoliolate  [ Botany ]

Unilocular [ Botany ]

Unisexual flower [ Botany ]

Unit to measure [ Physics ]

Unnatural [ Botany - Horticulture]

Unripe [ Botany ]

Unsegmeted [ Botany - Habit of growth ]

Unwater [ Horticulture ]

Unpot [ Horticulture ]

Uproot [ Horticulture ]

Uptake [ Biology ]

USDA (temperature zones) [ Botany ]