The botanical terms Monoecious and Dioecious are two distinct categories of plants based on their reproductive capabilities.
In this article, I will be making the distinction between Monoecious And Dioecious trees and plants, and provide you with an A-Z reference making it easier for you to identify which trees sit within each group.
What are Monoecious And Dioecious Trees and Plants
Dioecious Plants
Dioecious plants are self-sterile, meaning they require a male and female cultivar to successfully pollinate and produce flowers and thereafter seeds.
The male plants produce staminate flowers with male reproductive capacity, whilst females display pistillate flowers. It is estimated that 29% [1] of trees are dioecious.
Monoecious Plants
The majority of plants shrubs and trees 43% [1] are in fact Monoecious (translated as single house), meaning that they are able to complete the entire reproductive process from within a single plant and do not require any form of pollination from another plant.
They carry both male and female flowers for self-pollination. A critical consideration in horticulture and crop production
Winter squash is a great example of this dual function, where we can see thin stemmed male flowers as offshoots from the main vine stem, whilst the female flowers have thicker rounded flower stems. Once pollinated this thick stem swells and develops into a fruit. [2]
Monoecious plants have separate male and female flowers on the same plant.
Polygamo-dioecious plants have either female and bisexual flowers or male and bisexual flowers on the same plant.
A-Z List Of Dioecious And Monoecious Trees
A-Z Dioecious Trees
Acer negundo
Also known as Box Elder, this fast-growing species is native to North America. Often considered a weed tree and invasive.
Image: By Alexis CC by 4.0
Kiwi Fruit Vine
Vigorous, hardy plants that are easy to grow in a sunny sheltered spot, growing up to 28′ tall.
Image: Alexander Dunkel CC by 2.5
Tree of Heaven
Native to China but now widely distributed, this species grows up to 80 tall and is often used as an urban street tree. Alternating leaves down the stem, it will grow in most soils.
Image: By Kurt Stüber CC BY-SA 3.0
Norfolk Island Pine
Native to Norfolk Island in the Pacific Ocean, this tree is gigantic at 60 meters in height with a distinct erect conical-shaped habit.
Image: By Tree-species at Flickr CC by 2.0
Mulberry
A genus containing 10 species of fruiting tree, native to Asia and North America. A gnarly spreading habit makes for an attractive tree.
Image: Zeynel Cebeci CC by SA
Plum Yew
Erect habit, the Japanese Plum Yew produces small fruit of up to 1″ in length. This ornamental plant is native to Central and Eastern Asia.
Image: Plant Image Library CC BY-SA
Katsura Tree
An elegant medium-sized tree with heart-shaped leaves approximately 5″ in length, turning from bronze to pink through the season. Native to Japan and China.
Fringe Tree
Native to South Eastern USA the Fringe Tree grows with several tree trunks up to a height of 6m. A member of the olive family it produces masses of beautifully perfumed flowers.
Image: David Bender USFWS
Smoke Tree
Small to medium-sized trees often turn deep purple later in the season. Growing up to 8m tall they are generally considered a trouble-free, pest-free trees. Producing a frothy mass of flowers.
Ash Tree
A member of the olive and lilac family, the Ash tree is best known for its boomerang-shaped seed pods often referred to as helicopter seeds. Opposite leaves in pairs. The genus consists of around 45 species in the Northern Hemisphere.
As they age, Ash often changes sexual bias from primarily male to female.
Image: Rosser1954 CC by 4.0
Kentucky coffeetree
A member of the legume family the Kentucky Coffeetree is native to North America. The tree takes its name from the 10″ bean pod seeds that can be roasted and used as a substitute for coffee beans. This moderately fast-growing tree can reach 20m and live up to 150 years.
Image: Hardyplants
Honey Locust
Honey Locust can grow to 20m and exhibits legumes like seed pods in early autumn containing an edible pulp. This relatively fast-growing species can live 100+ years.
Image: Andrew Dunn CC by 2.0
Holly
Approximately 480 species in this evergreen family. This slow-growing plant can be found as climbers, shrubs, or trees and exhibits the unmistakable red fruits associated with Christmas.
Image: AnemoneProjectors CC by 2.0
Juniper
Coniferous shrubs of the Cypress family Juniper vary in size from tall narrow trees of 20-40m tall trees through to sprawling shrubs. This evergreen species display needle-like leaves and berry-like fruit.
Image: Ввласенко CC by 3.0
Dogwood
Also known as Japanese Dogwood, considered an ornamental flowering tree. Grows up to 12m tall and grows in a neat round habit.
Spicebush
An evergreen bush or small tree with a strong spice aroma, native to Asia and North America. The dried fruits are used as an aromatic cooking spice.
Image: Bee Inventory and Monitoring Lab
Osage Orange
A small tree or large bush this plant can grow up to 15m in height. A member of the Mulberry family, the fruit excretes a latex substance when cut. Its roots are thick and fleshy and have a bright orange bark.
Image: H. Zell GNU
Mulberry
A diverse plant with more than 200 species. Mulberry can grow up to 24m and are prized for their tasty fruits, as well as the trees use in the paper, silk, and pigment industry.
Image: JJ Harrison CC by 3.0
Mountain Holly
Native to North America the mountain holly is a deciduous shrub growing up to 4m tall. The leaves are 2 inches long and elliptical in shape. Male and female flowers are on separate plants.
Image: Rob Routledge CC by 3.0
Amur Cork Tree
The Amur Cork Tree is native to Asia and has been used in Chinese medicine to treat pneumonia, tumors, jaundice, and tuberculosis. The tree has both antibiotic and antimicrobial properties due to these alkaloids contained within the plant material.
The major chemical constituents of its bark are the isoquinoline alkaloids, berberine, palmatine, jatrorrhizine, phellodendorine with berberine found within the leaves. The indole alkaloid canthin-6-one has also been found in the roots of young trees.
The trees range from 8-12m tall and display leaves in opposite formations and change in color from green to a yellow bronze color tree in fall.
Image: Kurt Stüber CC by 3.0
Poplar
Renowned for its attractive white or grey bark the Poplar tree has a large genetic diversity. Growing up to 50m in height they are primarily dioecious a few species are monoecious. Catkins appear in early spring and range in color.
Willow
Prevalent in the Northern Hemisphere the Willow is a cross-compatible species with some variants growing up to 12m tall. Generally recognized for their overhanging relaxed flowing branches. Leaves are thin and elongated and the trees produce catkins in early spring.
Image: Didier Descouens CC by 4.0
Buffalo Berry
Buffalo Berry is a genus of small shrubs that produce a luscious mass of dark red berries. They have (non-legume) nitrogen-fixing roots. The berries are commonly used to make jams and preserves.
Image: Provincial Archives of Alberta
Prickly Ash
A genus of over 200 species in temperate through to sub-tropical regions. Alternately arranged leaves these woody climbers produce a fruit containing a single seed.
Image: Bee Inventory and Monitoring Lab
A-Z Monoecious Trees
Alder
35 species of trees and shrubs, the Alder found widely spread through Northern temperate regions. The male Catkin flowers are long whilst the female is shorter. Due to their abundance, these species deliver large volumes of nitrogen to enrich forest soils.
Image: Vassil
Birch
Small to medium-sized shrubs and trees are distributed across the Northern hemisphere. Displaying attractive papery bark in white, grey, yellow black, or silver gives the species their names. Catkins are produced in early spring and flowers open before or with leaf buds.
Image: Shizhao CC by 3.0
Hickory
The Hickory tree flowers are small yellow catkins that require wind pollination. The fruit they produce is a small spherical or oval nut contained within a boney shell. The most notable of which is the pecan nut.
Image: Ana Beatriz Vega González CC by 4.0
False Cypress
A native to Japan the False Cypress is a genus of conifer and ranges from 20-70m in height. This ornamental is often used in topiary borders.
The wood grain of the False Cypress is very straight and lends itself to use for making arrow shafts, boat hulls, decking or flooring, guitar fretboards, and various interior millwork applications. It also exhibits a high resistance to rot.
Image: Derek Ramsey GNU
Hazel
Native to the Northern Hemisphere and most commonly known for its edible fruit the hazelnut. The tree puts out catkins of 3-5 inches long very early in spring ahead of leaf buds. They can live for up to 8o years and grow to a height of approximately 12m.
Image: Rosser CC by 4.0
Cypress
An evergreen conifer can grow as a shrub or tree up to 40m tall. Exhibiting short-scale-like leaves grouped in fours. The flower appears like tiny buds at the twig tips. Pea-size cones will ripen from female flowers. Popular varieties include Leyland Cypress and the larger Thuja Green Giant Arborvitae a fast-growing tree used for planting hedging in residential landscaping.
Image: MPF CC by 3.0
Beech
Wind pollinated by tassel-like male catkins, this majestic tree exhibits torpedo-shaped lime leaves that darken as they mature. The edges of the leaves are typically hairy. Not to be confused with Hornbeam.
Image: Plant Image Library CC by 2.0
Fig
Over 850 species are native to tropical or subtropical climates with some species habiting a semi-warm Mediterranean environment. Most species of the fig tree are evergreen and their soft large teardrop-shaped fruit is a fundamental part of each ecosystem they occupy.
Image: Wendy Cutler CC by 2.0
Larch
Growing up to 60m in height this conifer is broadly distributed across the Northern Hemisphere. One of the rare deciduous conifers they drop their needle-like leaves in Fall/Autumn. The male cone is orange in color whilst female cones are green or purple, turning brown when mature and dry.
Image: Chris Light CC by 4.0
Hop Hornbeam
Hardwood species that is native to Europe, Asia, Central, and North America. Distinctive lance-shaped leaves that turn an attractive yellow in Fall/Autumn. Produces catkins early spring.
Image: Plant Image Library CC by 2.0
Spruce
Picea consists of around 35 species of coniferous evergreen trees ranging from 20 to 60m tall. Attractive green needle-like leaves with variable-sized cones and scaling amongst the Spruce species. From tall upright habit to low weeping evergreen varieties, a popular and colorful ornamental tree.
Image: JJ Harrison CC by 3.0
Pine
Coniferous, resinous, evergreen trees the Pine genus contains over 120 species. It is possible for Pine trees to live up to 1,000 years and grow up to 80m tall. Broadly distributed across the Northern Hemisphere the pine has both ornamental and industrial use qualities. Primarily a monoecious species with female and male cones on a single tree, although there are also some single-sex varieties.
Image: Walter Siegmund GNU
Sycamore
Capable of reaching heights of up to 50m the Sycamore often displays a beautifully mottled bark. Commonly splits into several trunks fixed down with fibrous roots. Hanging flowers up to 6 inches in length.
Image: Andrew Hill CC by 3.0
Golden Larch
The Golden Larch is not actually a true larch, it is more closely related to Cedrus and Abies. Native to Eastern China this coniferous tree will grow in excess of 35m in mountain regions. The needle-like leaves are 1-3 inches in length and turn golden prior to falling from the tree at the end of the season.
Image: By William (Ned) Friedman
Douglas Fir
An evergreen coniferous tree, native to North America capable of growing up to 100m tall. Needle-like leaves are flat and splay out to completely encircle the branches of the tree. The bark is an attractive green-gray color on young trees ad heavily scented.
Image: Luis Alejandro Apiolaza CC by 4.0
Oak
There are over 500 species of Oak, they have a spiral arrangement of leaves surrounding the distinctive acorn nut mounted on a cup-like appendage. The Male flowers appear as green catkins with female flowers developing as clusters of bracts.
Image: Robert Flogaus-Faust CC by 4.0
Citrus Tree
Rutaceae is more commonly known as Citrus family, Sapindales or sometimes called Rue. Ranging from Citrus Trees, inclusive of Lemon, Orange, Lime to smaller shrub-like herb varieties. This is a widely distributed family with a very complex genus due to considerable hybridization. There are 160 genera with an estimated 1600 species.
Umbrella Pine
The Umbrella Pine is not a genuine Pine Tree. It is in fact the only species in the genus and is more commonly referred to as the Japanese Umbrella-Pine. The tree has no immediate relatives but can be traced back to fossil records over 200 million years old.
It is an evergreen tree that grows up to 25m in height and produces cones that are 2-4 inches in length and take 18 months to mature.
Image: Rae CC by 2.0
Bald Cypress
A very hardy species capable of withstanding extreme conditions. This deciduous conifer displays greyish bark and grows to heights of 40m. The tree flowers in spring and seeds mature in late October and the cone opens.
Image: David Ohmer CC by 2.0
References
[1] Popovic, Zorica & Stefanović Marković, Milena & Smiljanic, Miroslava & Matic, Rada & Kostić, Miroslav & Vidaković, Vera & Bojovic, Srdjan. (2012). Sex expression in serbian dendroflora – A case study of Fraxinus ornus var. Angustifolia. Archives of Biological Sciences. 64. 107-111. 10.2298/ABS1201107P
[2] Botanical Terminology: Flowers, Houses, and Sexual Reproduction. Cindy Haynes
About The Author
Ben Hilton is a Horticultural writer, lifetime gardener, and Founder of The Yard and Garden. Contact Ben here or follow him on Twitter @_YardandGarden