INDIGENOUS: Plant species that are native to that region. These plants are believed to be growing in the wild at least for the span of human history.

INDIRECT SUNLIGHT: Diffused light, as opposed to the direct rays of the sun, such as that on the north side of a house or in the shade of thick woods.

INDETERMINATE: Being able to grow for an indefinite period of time.

INFERTILE : Soil that has no nutrients.

INFLORESCENCE: The arrangement of flowers on the stem. A flower head.

INOCULANT: A microorganism which is introduced into the soil to improve growth of legume crops.

INOCULANTION: The addition of rhizobia to the soil, or applying it to the seed, prior to planting.

INORGANIC: A chemical or fertilizer which is not obtained from a source which is or has been alive.

INSECTICIDAL SOAP: A specially prepared, biodegradable soap made from natural fatty substances that kills many insects on contact without damaging plants or harming people, animals, or beneficial insects.

INSECTICIDE: A chemical (synthetic or organic) used to kill or repel insects.

INSECTIVOROUS PLANT: Another term for carnivorous plants. Plants that will trap and digest insects that will supply them with nitrogen. Most of these plants grow in swamps where it is difficult to obtain nitrogen.

INSITU: The act of sowing seeds or cuttings in the ground where they are to grow.

INTERCROPPING or INTERPLANTING: A smart way to garden. Mixing two or more plants, tall and short, for foliage difference, or combining plants that bloom at different times of the year.

INTERNODE: The area on a stem between nodes.

INTERPLANTING: Mixing two or more plants, tall and short, for foliage difference.

INVASIVE: The ability of a plant to spread quickly and crowd out other plants.

IRON CHELATE: A form of iron readily absorbed by plants, especially in alkaline soils.

IPM: Integrated Pest Management. A method by which gardeners can learn to manage and eradicate pests by choosing appropriate plants providing good growing conditions and minimizing pests rather than annihilating them.