Difference Between Dioecious and Monoecious Plants

Blue Princess holly produces a lot of berries (image) for me. Blue Prince is the male.
Blue Princess holly can be a prolific berry-producer, provided she has a 'Blue Prince' around to pollinate her.

The Spruce / David Beaulieu

"Dioecious" and "monoecious" are terms that refer to plant reproduction in horticultural descriptions. Dioecious (dahy-EE-shuhs) describes a plant group that includes distinct male and female plants. Monoecious (muh-NEE-shuhs describes a single plant that bears both male and female flowers.

The Prefix Tells the Story

An easy way to remember the meanings of dioecious and monoecious is to look to the Greek prefixes di, which means two, and mono, which means one. With dioecious species, each plant is either a male or female member. Some plants of the species have only male reproductive organs, or stamens, while other plants of the species have only female reproductive parts or pistils.

With monoecious species, each plant has some flowers with stamens and some flowers with pistils.

Illustration of dioecious and monoecious plant differences
Illustration: Ellen Chao. © The Spruce, 2019

Practical Differences

When the plants are dioecious, you must have at least one corresponding male plant growing in or around your landscaping for the fruit-bearing female plants to be pollinated. For example, holly shrubs (Ilex) are dioecious plants. To get good berry production from a 'Blue Princess' holly shrub, you need to supply a male cultivar to do the pollinating.

This naturally raises the question of how to tell the genders apart. Quality garden centers clearly label their dioecious plants so you know whether you're buying a female or a male cultivar. However, you can learn to tell a male holly apart from a female holly (or any other dioecious plant) on your own. Look for stamens, usually loaded with pollen, that indicate a male plant.

Fun Fact

A monoecious plant reproduces (that is, blooms and sets seed) all on its own and does not need a partner. For example, if you are buying a red-twig dogwood shrub (Cornus alba) for its berries, then you only have to buy one plant.

Unisexual Flowers vs. Bisexual Flowers

Dioecious and monoecious plants have something in common, in that they both bear unisexual flowers with only male or female reproductive parts. If the plant is dioecious, the male and female blossoms appear on separate plants. If the plant is monoecious, each plant has both male and female flowers.

By contrast, some plants have blooms that are bisexual. Each bloom has both male and female parts. The process of reproduction occurs right within the individual flowers. These are sometimes referred to as "perfect" flowers because the pollinations process is self-contained within a single flower. An example of a plant with perfect flowers is the lily (Lilium).

Close-Up Of Pink Lily
Anand Swaroop / EyeEm / Getty Images

Short List of Dioecious Plants

Most of the landscape plants home gardeners grow are either monoecious or the plant produces bisexual flowers, so you don't have to give them much thought in terms of reproduction. With dioecious plants, you must have male and female plants to ensure the females that will bear berries or seeds. In addition to holly, here are some common dioecious plants you might want in your landscape:

  1. American bittersweet vine (Celastrus scandens)
  2. Aspen tree (Populus tremuloides)
  3. Bayberry shrub (Myrica pensylvanica)
  4. Ginkgo biloba tree (scientific and common name are the same)
  5. Juniper shrub (Juniperus)
  6. Ornamental kiwi vine (Actinidia kolomikta)
  7. Mulberry tree (Morus alba)
  8. Pussy willow bush (Salix discolor)
  9. Swamp tupelo tree (Nyssa sylvatica)
  10. Sweetfern shrub (Comptonia peregrina)
  11. White ash tree (Fraxinus americana; do not grow the males if you are an allergy-sufferer)
  12. Yew shrub (Taxus)
Article Sources
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  1. Botanical Terminology: Flowers, Houses, and Sexual Reproduction. Iowa State University Extension and Outreach