- Keel
- The two anterior united petals of a flower.
- Kelp
- Any of various large brown seaweeds, sometimes used to enrich poor soil.
- Key
- A dry, one-seeded fruit with a wing, particularly that of the maples.
- Kitchen garden
- A garden where vegetables, fruits and herbs are grown for use in cooking.
- Knocking out
- The temporary removal of a plant from its pot in order to check the condition of the root ball.
- Knot garden
- An elaborately designed garden consisting of flowers, herbs and/or low shrubs arranged in intricate, geometric knot-like patterns when seen from above.
