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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Botanical Terminology: Flowers, Houses and Sexual Reproduction

This article was published originally on 2/4/2009

Monoecious and Dioecious - What language is this? These botanical terms sound like a description of some kind of tempting dessert. Actually, these are terms used to describe the reproductive behavior of some plants. Not all plants have perfect flowers. "Perfect" in a botanical sense means that each flower has both male and female parts in the same structure. Lilies, roses, and apple flowers are perfect.

Before you decide that this topic is too technical for you - just wait! You like squash, right? You want pretty holly berries in your landscape, right? These are plants where the difference between "monoecious" and "dioecious" matters.

Monoecious plants have male flowers and female flowers in separate structures on the same plant. "Mono" means one - and the term "monoecious" is literally "one house". The same plant houses different flowers, some being male the others being female. Squash is monoecious. If you take a close look at squash flowers you can soon tell which are female because they have a tiny fruit at the base. For obvious reasons, the male flowers don't. Knowing that only the female flowers produce fruit and that only 50% of the flowers on squash are female can save some heartache when all the flowers on the plant don't produce fruit.

Dioecious plants house the male and female flowers on different plants. So not only does the plant have separate male/female flowers, they have male plants (with only male flowers) and female plants (with only female flowers). Hollies and asparagus are dioecious. Since only the female plants can produce the fruit, hollies must have a male plant and a female plant in close proximity.  Male holly plants are often given masculine names like 'Southern Gentleman', 'Jim Dandy', or 'Blue Prince', so they are easy to recognize. In the landscape, one or two male hollies are often tucked behind the female hollies to ensure pollination and fruit set and to hide the male plants that don't produce the showy fruit.

The male cultivars of asparagus are more popular with gardeners than the females. This is because the male spears are larger, they don't waste any effort on fruit production. Male plants can also be neater. Male ash trees don't produce the "canoe paddle-like" fruits like the females. Male trees of Kentucky Coffeetree, Cork Tree, and Ginkgo are popular for the same reason - no messy fruit!

So knowing the difference between plants with perfect, monoecious, and dioecious flowers can be important when gardening. It also can make you sound like a gardening expert - try dropping "monoecious" on your guests at your next dinner party. If you are serving squash, it should be easy to explain!

Year of Publication: 
2009
Issue: 
IC-500( 2) -- February 4, 2009