''Alyssum alyssoides'' is a species of flowering plant in the

mustard family Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The l ...

known by several common names, including pale madwort and yellow alyssum. It is native to Eurasia, but it can be found throughout much of the temperate world as an

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived the ...

and sometimes a common

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

. For example, it has been noted as a weed in the western

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. It often appears in arable fields, sandy tracks, pits, and docks.

Description

This is a hairy annual or biennial herb producing stems which grow upright or lie along the ground to a maximum length of 30 to 40 centimeters. It produces yellow

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

s May–July that fade to white with four small

petal Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usuall ...

s about 1.5–3 mm long. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...

is a round, hairy capsule up to half a centimeter long. The hairs are branched, often stellate (star shaped). The

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...

s are tiny, 1–2 mm long, with minuscule wings. The leaves are simple, narrowly oblanceolate or linear with smooth margins, and are alternately arranged.

References

External links

Jepson Manual TreatmentUSDA Plants Profile
* alyssoides Flora of Asia Flora of Europe Plants described in 1759 Taxa named by Carl Linnaeus {{Brassicales-stub