Inflorescence
Collective name for a group of individual flowers. The grouping can take many forms: a spike, where the blooms are closely packed along a vertical stem; an umbel or a corymb, where the blooms form a flattened dome; the complex hierarchical arrangement called a panicle, or the tightly packed disc flowers in the center of a daisy, called a capitulum.
Insecticidal soap
A specially formulated soap that is only minimally damaging to plants, but that kills insects primarily causing their outer shell to crack, which allows the insect's interior organs to dry out.
Insecticide
Any material that kills insects. There are numerous botanical and mineral powders that are toxic to insects, as well as biodegradable chemicals such as insecticidal soaps.
Integra
A latin word used in plant naming meaning - entire.
Intercrop
One crop that is grown between the rows of another. the term is also used to describe the practice of alternating the plants of two crops within a single row, like slow growing cauliflower and faster growing lettuce.
Internode
The part of a stem that is in between nodes.
Invasive
Describing plants that spread out of control through runners, seeds or rhizomes - like Mint, Agapantha, some grasses, Calendula, Barberry, Nandina domestica, Prickly Pear and many others.
Involucre
One or more whorls of bracts at the base of the flower.