Underwatering: Cultural problem which describes an African Violet that is not receiving enough water. While it is often said that underwatering is better than overwatering, underwatering can be just as dangerous. Paradoxically, underwatering can contribute to the same problems as overwatering, i.e., Crown Rot, Root Rot and Pythium. More information.
Undulate (1): Bloom type. See Frilled.
Undulate (2): Leaf type. See Ruffled.
Unicover: Decorative container sometimes used to cover a pot. Usually made of plastic.
Unrestricted Use: See General Use.
Unspaced: Refers to a commercially-grown African Violet which has not quite developed enough for its last spacing, which is completed just before the African Violet becomes pre-finished. A standard, unspaced African Violet is normally 27 to 29 weeks old and will not have begun it first flowering cycle.
Upper Epidermis: The top surface of a leaf. See Epidermis.
Urea: A synthetic source of nitrogen derived from natural gas. Nitrogen which has been formulated from urea can be dangerous to African Violets, because urea causes Root Burn.
Urea Nitrogen: Nitrogen which comes from urea, an inexpensive source of nitrogen which has been synthesized from natural gas. Urea nitrogen is not recommended for African Violets, since it can cause Root Burn.
Usambara Mountains: Mountains, now in northeastern Tanzania, where the first recorded discovery of African Violets was made.
Utah: Optimara variety. Medium, standard African Violet (4-inch pot size) with single, two-tone blue flowers and medium green leaves. Introduced 1987. (AVSA Reg. No. 6603) More information.
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