O

Ob- [ Prefix ]

Obclavate [ Botany ]

Obconic [ Botany ]

Oblanceolate [ Botany ]

Obligate [ Biology ]

Oblique [ Botany - Morphology ]

Oblong [ Botany - Morphology ]

Obovate [ Botany ]

Obovoid [ Botany ]

Obsolete [ Taxonomy ]

Obtuse [ Botany ]

Occurrence [ Ecology ]

Off-seasoning [ Botany - Horticulture ]

Offset or Offshoot [ Botany ]

Offspring [ Biology ]

Oil [ Botany - Biochemistry]

Ontogenesis [ Biology ]

Opaque [ Botany - Morphology ]

Open areas [ Ecology ]

Opportunistic grower [ Ecology - Botany ]

Opposite [ Botany ]

Order  [ Taxonomy ]

Orbicular  [ Botany ]

Orb-shaped  [ Botany ]

Organ [ Biology ]

Organelle [ Biology - Cell anatomy ]

Organic [ Biology - Chemistry ]

Organic cultivation [ Agronomy - Horticulture ]

Organic fertilizer [ Agronomy - Horticulture ]

Organic matter [ Ecology - Agronomy - Pedology ]

Organism [ Biology - Physiology - Ecology ]

Orientation [ Ecology - Landscaping ]

Origin [ Botany ]

Original description [ Taxonomy ]

Original diagnosis [ Taxonomy ]

Original publication [ Taxonomy ]

Ornamental plant [ Botany - Horticulture ]

Ornithophily [ Botany ]

Ortostich [ Botany ]

Osmosis [ Physiology - Chemistry ]

Outdoor cultivation [ Horticulture ]

Oval [ Botany ]

Ovary [ Botany ]

Ovary wall [ Botany ]

Ovate [ Botany ]

Ovate leaf [ Botany ]

Over-collection (Over-exploitation) [ Ecology ]

Overground [ Botany ]

Overheating [ Physiology -Botany ]

Overpotting  [ Horticulture ]

Overripe  [ Botany ]

Overstorey  [ Botany - Ecology ]

Overwatering [ Horticulture ]

Overwintering [ Botany - Horticulture ]

Ovoid [ Botany ]

Ovule [ Botany ]

Ovum (Plural: Ova) [ Botany ]

Own-root (plants) [ Horticulture ]

Oxygen [ Physiology - Chemistry ]