Type of inflorescence in which all pedicles (floral stalks) eradiate from a common point. E.g., geranium, gardenia. One can also say the umbel is a raceme whose axis did not elongate: the younger flowers are in the center and the older gradually distal. (Also see Raceme, Inflorescence).
Undulated
Leaf or petal with wavy margin. The term is not applied to serrated or toothed margins.
Unisexual
Monoecious or Dioecious plants in which the flower are male or female; flower that is not hermaphroditic, but is either male or female. (compare with Hermaphrodite).
Humus: Mixture of plants and other partly decomposed plant parts, mixed with soil to enrich it with nutrients. Humus presents bacterial properties and makes the soil mix more porous. It can be found under deciduous trees or prepared with decomposing leaves. The term humus (or compost) can also be used to define the material formed by decomposition of animal and plant remains; vermicompost (or worm humus) is used to define the mix resulting from worm excrement and the soil used for its production – this mixture is extremely rich in nutrients that enrich it and give porosity to the soil used in plant cultivation.