Microgreens Glossary
Plain-language definitions for the terms that show up repeatedly in microgreens guides, grow rooms and community discussions.
Blackout
A period after germination when seedlings are kept in darkness to encourage additional stem elongation before they are moved into light.
Bottom watering
Adding water beneath a drainage tray so the growing medium absorbs moisture from below instead of repeatedly wetting the canopy.
Cotyledons
The first seed leaves that open after germination. Microgreens are commonly harvested when cotyledons are fully developed and early true leaves are emerging.
True leaves
The leaves that develop after the cotyledons and begin to resemble the mature plant’s normal leaf shape.
Brassica
A plant family that includes broccoli, radish, cabbage, kale and mustard. Many brassicas are fast, beginner-friendly microgreens.
Seed density
The amount of seed sown over a given tray area. Too much seed can increase crowding, stretching and moisture problems.
Germination
The stage when a seed absorbs moisture and begins producing a root and shoot.
Weighted germination
A germination method where another tray or weight applies gentle pressure to improve seed-to-medium contact and encourage strong rooting.
Root hairs
Fine white structures attached directly to roots that help absorb water. They are often mistaken for mold when seedlings first emerge.
Damping off
A general term for seedling collapse associated with disease pressure, often favored by persistently wet, poorly ventilated conditions.
Canopy
The combined layer of leaves and stems across the top of the tray.
PPFD
Photosynthetic photon flux density, a measure of the usable light reaching a plant surface. It is more specific than judging a grow light only by watts.
Soilless mix
A growing medium formulated without field soil, often using materials such as peat, coir, perlite or vermiculite.
Coco coir
A fibrous material made from coconut husk that is commonly used as a lightweight growing medium.
Growing mat
A thin fiber-based substrate made from materials such as hemp, jute, wood fiber or coir that replaces loose growing medium in some systems.
Succession sowing
Starting new trays on a repeating schedule so harvests occur continuously instead of all at once.
Crop cycle
The full period from sowing through germination, lighted growth and harvest.
Food-contact surface
Any tool, container or surface that directly touches harvested food and therefore needs appropriate cleaning and sanitation.