Botanical sexism is a term coined by horticulturist Tom Ogren to describe the planting of male plants instead of female plants of certain dioecious species including:

willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

s, poplars,

aspen Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section ''Populus'', of the '' Populus'' genus. Species These species are called aspens: *'' Populus adenopoda'' – Chinese aspen (Chin ...

s, ashes,

silver maple ''Acer saccharinum'', commonly known as silver maple, creek maple, silverleaf maple, soft maple, large maple, water maple, swamp maple, or white maple, is a species of maple native to the eastern and central United States and southeastern Canad ...

s, pistache, mulberry, pepper tree and other woody plants such as junipers, yew pines, fern pines, wax myrtles, alpine currants,

plum yew Plum-yew is a common name for several plants and may refer to: *''Cephalotaxus ''Cephalotaxus'', commonly called plum yew or cowtail pine, is a genus of conifers comprising 11 species, treated in either the Cephalotaxaceae, or in the Taxaceae w ...

s, and yews According to Ogren, pollen allergies have been amplified due to the planting in urban areas of male

clones Clone or Clones or Cloning or Cloned or The Clone may refer to: Places * Clones, County Fermanagh * Clones, County Monaghan, a town in Ireland Biology * Clone (B-cell), a lymphocyte clone, the massive presence of which may indicate a pathologi ...

which increases the amount of pollen in the air. Male plants are commonly used in urban areas because plants with female flowers produce

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 particu ...

s and flowers that litter the landscape. The planting of more female plants would decrease the overall amount of pollen since they do not produce pollen and remove pollen from the air for

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

. The theory has existed since at least the 2000s. Biological sexism is used in the

Ogren Plant Allergy Scale The Ogren Plant Allergy Scale (OPALS) is an allergy rating system for plants that measures the potential of a plant to cause allergic reactions in humans. Scale system The OPALS allergy scale was first published in ''Allergy-Free Gardening'', b ...

(OPALS), which has been adopted by the

United States Department of Agriculture The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...

. Botanical sexism has found some scientific acceptance as a reason for increased allergies and asthma; however, other scientists have also been critical of it, stating that it only applies to certain trees and is not as widespread as Ogren alleges.

References

Allergology {{Botany-stub