Being Dioecious – Male and Female Plants

Plants with colorful or tasty fruit are valued by many of us for their beauty, as food, or both. I am a big fan of wild Persimmon and Red Mulberry, for example, but not every Persimmon or Mulberry tree in the woods will have fruit. And there is a perfectly good reason why. Male plants will never bear fruit – they can only produce the pollen needed by nearby female plants to form those tasty treats I seek.

Plants that have male and female reproductive structures in separate plants are referred to as dioecious: meaning “two houses” (di=two, oecious=house). It turns out that many common plants in nature are just so, with any given plant having either male or female flower parts. These types of flowers are referred to as imperfect flowers. Both types can have petals, but staminate flowers bear only long filaments that hold pollen at the tips, while pistillate flowers typically have what looks like a vase-shaped ovary, with a stalk having a sticky end to trap pollen, often delivered by a pollinator.

I am often asked why a certain type of plant in someone’s yard has never had fruit, like Yaupon Holly, Persimmon, or Red Mulberry. Hollies, Wax Myrtle, Gallberry, Black Gum, Red Bay, Horse Sugar, Wild Olive, Groundsel, and many other common plants are also dioecious species. A forester once suggested that nearly 70% of Red Bay plants in our woodlands are males – why is a mystery. Given how hard it seems to find a female Persimmon or Red Mulberry, the same may well be true for those species as well.

Imperfect flowers are not, however, confined to dioecious species. Corn and many other grasses also have imperfect flowers, but on the same plant – referred to as monoecious (one house) species. The male or staminate flowers on corn are borne at the top of a mature plant, with the female or pistillate flowers lower on the stalk – the ears that have long tassels that collect the pollen that falls upon them, and deliver that to the many ovaries on the cob that will form the kernels we eat.

Back to the point about why we like colorful fruit, it can be frustrating to use these species of plants in landscaping, if the fruit is the selling point. A nice row of Yaupon Holly or Wax Myrtle plants will look quite different with a mixture of females with bright red berries next to berryless male plants. Most nurseries that sell these species have plants raised from seeds, meaning that about half will be male and the other half female. But, until they are mature enough to produce flowers, they look the same. In order to guarantee male or female plants, producers grow them from cuttings.

In any case, having a fruitless dioecious plant is not the end of the world. The foliage is often as attractive as the flowers. Besides, your male plants are important sources of pollen for the nearby fruit-bearing plants, even if they are in your neighbor’s yard. Another great reason to be friendly to all your neighbors, if only to be invited to share in the bounty of yummy fruit.

Hope to see you in our great outdoors!