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Allium cepa

Species category

Vegetable

Common name

garden onion

Diagnostic characters

Planting unit

True seedTrue seed:
A mature fertilized ovule consisting of an embryo, with or without and external food reserve (e.g., endosperm) enclosed by the testa.

Shape

Wedge

Size

  • Length: 3 mm
  • Width: 2.5 mm
  • Thickness: 2 mm

Color

Black

Texture

Minute stipplesStipples:
Numerous small dots or specks.

Embryo

Size: Partially fills the seed.

Shape: Linear, but slightly curved in the seed.

EndospermEndosperm:
Nutritive tissue originating from union of the two polar nuclei with a sperm nucleus.
: Axial, hard and translucent grey-colored.

(SIG 2026SIG 2026:
Seed Identification Guide (SIG). 2026. Accessed March 2026.)

Other structures

HilumHilum:
The scar on the seed coat at the place of its detachment from the seed stalk (funiculus).
 enfolded at tip.

Identification notes

A seed is generally wedge-shaped but usually has one flat surface. Onion seeds of different species are difficult to separate.

Noxious weed seed categories

State Noxious Weed: Alabama, Arkansas, Delaware, Georgia, Kansas, Kentucky, Louisiana, Massachusetts, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia

AOSA examination list

Included

More information

For more information, see ISMA fact sheet.

Nomenclature

Family

Liliaceae (USDA-NRCS 2026USDA-NRCS 2026:
United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2026. The PLANTS Database. National Plant Data Team, Greensboro, NC USA. Accessed March 2026.)

Amaryllidaceae (USDA-ARS 2026USDA-ARS 2026:
United States Department of Agriculture-Agricultural Research Services (USDA-ARS). 2026. Germplasm Resources Information Network (GRIN). Accessed March 2026.)

Valid name

Allium cepa L.

Synonyms

Allium cepa L. var. aggregatum G. Don
Allium cepa L. var. cepa
Allium cepa L. var. multiplicans L.H. Bailey
Allium cepa L. var. proliferum (Moench) Regel
Allium cepa L. var. solaninum Alef.

Allium cepa. Wedge-shaped seeds with one flat surface.
Allium cepa. Wedge-shaped seeds with one flat surface.
Allium cepa . Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa. Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa . Scale marks are millimeters.  Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa. Scale marks are millimeters.  Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa . Scale marks are millimeters.  Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa. Scale marks are millimeters.  Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa . Showing surface texture. Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa. Showing surface texture. Photo by Norma Diaz, USDA APHIS PPQ.
Allium cepa . Photo by Kelly Ryan, USDA APHIS PPQ.
Allium cepa. Photo by Kelly Ryan, USDA APHIS PPQ.
Allium cepa var. cepa . Photo by Madeline Maher, USDA-APHIS-PPQ.
Allium cepa var. cepa. Photo by Madeline Maher, USDA-APHIS-PPQ.