Gardening Terms

Glossary of Terms

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obcordate
Heart-shaped with the notch at the tip rather than at the base. Learn more.

oblanceolate
Reverse of lanceolate; broadest above the middle and tapering toward the base. Learn more.

oblong
Longer than broad, with nearly parallel sides. Learn more.

obovate
Shaped like an egg, with the broader end at the top. Learn more.

oedema
a blister-like swelling in plant tissues caused by excessive water uptake. Learn more.

oedema (edema)
Swelling or blistering of leaves due to excessive water uptake and poor transpiration. Learn more.

oomycete
Fungus-like microorganisms responsible for diseases such as downy mildew and root rot. Learn more.

open-pollinated
Plants pollinated by natural mechanisms, producing offspring true to type if isolated. Learn more.

opposite
leaves or buds arranged in pairs at the same level on opposite sides of a stem. Learn more.

organic certification
A process verifying that food or products are produced according to organic farming standards. Learn more.

organic matter
Decomposed plant or animal residues that improve soil fertility and structure. Learn more.

organic mulch
Mulch derived from plant or animal materials such as leaves, straw, or bark. Learn more.

ovary
The part of the pistil that contains ovules and develops into fruit. Learn more.

overseeding
Sowing seed into existing turf to thicken coverage or introduce new varieties. Learn more.

overwinters
the ability of an organism or plant to survive through the winter season in a dormant or protected state. Learn more.

ovule
The structure within the ovary that develops into a seed after fertilization. Learn more.

oxalate/oxalic acid
a naturally occurring acid in plants; high concentrations can be toxic. Learn more.