Do you have a garden and you’re looking to take your green thumb to the next level? Then, you need to properly understand plant biology. Don’t worry, it’s not that complicated. You just need to know botanical terms that describe plant reproduction, growth, and some aspects of plant life.

That said, let’s get started with some details about monoecious, dioecious, and polygamous plants. By the time you’re done reading this, you’ll find yourself impressing your gardening friends.

What are Monoecious Plants?

What is the difference between Monoecious, Dioecious & Polygamous plants

What is the difference between Monoecious, Dioecious & Polygamous plants?

Monoecious plants (/məˈniːʃəs/) are those plants with both the male and female reproductive systems existing on them. What this means is that they have some flowers that are male, the others are female. Also, those plant species that can pollinate themselves are referred to as “self-pollinating.”

Let’s take corn for example – this is a good example of a monoecious plant. With corn, the tassel is the male reproductive part while the developing ear is the female. 

The ear or female reproductive portion houses the stamen and pistil for the plant, while the male portion or tassel contains the pollen. At the right time, the pollen falls onto the silk, which pollinates the corn.

Also, you can remove the tassel or male portion of the corn and artificially pollinate the female portion or ear by hand. This way, you can create an entirely different variety – this cross-pollination is actually normal in modern plant science.

A common setback when it comes to self-pollinating monoecious plants is the risk of cross-pollination. The pollen from an entirely different variety but of the same species can fall onto the female stamen of the same species but a different variety.

Why is this an issue? Well, the resulting hybrid can be totally unpredictable – you have no idea what you’re going to get.

You should also know that it’s possible to have monoecious plants that are self-sterile – they need the pollen of another plant for them to pollinate.

Another excellent example of monoecious plants is the Musa plant or banana (actually a perennial herb) – it also has a large inflorescence with rows of male and female flowers. 

Squash is also a monoecious plant. Only around half of the blooms on it actually develop fruits – this is because only half are female.

A lot of the plants you have in your garden are monoecious – they have perfect flowers with male and female parts in the same flower. Lilies, Coconut, Chara, and Cucurbit are also good examples of monoecious plants.


What are Dioecious Plants?

By now you must have guessed what dioecious plants are – the male and female reproductive systems are found on separate plants.

Even though both plants produce flowers, one has the female reproductive parts while the male portion is on the other plant. This is quite different from monoecious plants where one plant has both female and male flowers. 

As a horticulturist, knowing which plants are dioecious is crucial, especially when planning your garden or landscape. This way, if you want to buy plants like asparagus, blueberries, bittersweet, or holly that are dioecious, you’ll know that you need to buy both the male and female plants – that’s the only way they can have fruits.

For dioecious plants to successfully pollinate they need two separate plants – with only the female part bearing the fruits. Let’s take holly for instance – one male plant can pollinate up to ten female plants.

Blueberry Plants (Vaccinium corybosum)

Blueberry Plants (Vaccinium corybosum)

You should also note that some fruit trees are dioecious – they need another tree for successful pollination. Just like with dioecious plants, the fruits can only be found on the female trees. A good example of a dioecious tree is the ginkgo tree.

If you’re getting fruit-bearing dioecious plants from a nursery, look out for labels – most are clearly sexed and labeled. But, in some cases, like blueberries, it is indicated by the name – the male is called “blue boy” while the female is “blue girl.”

With holly plants, a common dioecious plant, the male plants have flowers with anthers, but on the female plants, the flowers have the pistil – this contains the ovary, style, and stigma.

If you want dioecious plants in your garden, then you need proper planning. For instance, if you want pretty red holly berries in your garden, you need to get both the female and male plants. 

The good part is, having dioecious plants gives you more options. Take asparagus for instance – the male plants are more common in gardens. Since they don’t produce fruits, they channel that energy into producing cleaner and larger spears. Also, with the ginkgo tree, you can decide to go with the male tree so that your garden is not littered with messy fruits (if you live in the tropics!)

A Simple Way To Remember

If you want to easily remember the meaning of monoecious and dioecious plants, just look at their prefixes – mono means one while di means two.

Dioecious plant species have a male or female member. Only the stamens or male reproductive organs is present in some plants of the species, and on the other hand, other plants of the species have only the pistils or female reproductive organs.

With monecious species, some flowers have pistils and some have stamens, all on the same plant. Simple, isn’t it?


Comparing Bisexual and Unisexual Flowers

There’s one thing that’s common with monoecious and dioecious plants – they both produce unisexual flowers that have only female or male reproductive organs. 

If your plant is dioecious, you’ll find the female and male flowers on separate plants. But, if it’s monoecious, then each plant will have both female and male blossoms.

We also have some plants that have bisexual flowers. In this case, each flower has both female and male organs – here, reproduction happens within each flower. These blossoms are referred to as “perfect” flowers – pollination is self-contained within each flower. A good example is Lilium.


Differences Between Monoecious and Dioecious Plants

Ilex aquifolium 'Argentea Marginata' - Female Silver Variegated Holly

Ilex aquifolium ‘Argentea Marginata’ – Female Silver Variegated Holly

If you are still a bit confused about how monoecious plants are different from dioecious plants, look at it this way; with dioecious plants, you need to grow at least one corresponding male plant in or around your garden if you want to pollinate the fruit-bearing female plants.

Take Ilex or holly shrubs for example; you need a cultivar for pollination if you want to get a Blue Princess holly shrub to produce berries.

The question now is, how do you differentiate the genders? Like we said earlier, some garden centers ensure their dioecious plants are clearly labelled – you can easily tell if you’re buying a male or female cultivar. 

If you don’t see any labels, you can easily learn how to tell a female dioecious plant from a male. Just check for stamens packed with pollen – this tells you that it is a male plant.


What are Polygamous Plants?

We can talk about plant reproduction and not mention polygamous plants. 

Also referred to as polygamomonoecious or trimonoecious, these are flowering plants that have both bisexual and unisexual flowers, all on a single plant – this easily promotes cross-pollination.

What this means is that the plant may have both bisexual and female flowers, known as gynomonoecism, or bisexual and male flowers, referred to as andromonoecism. Interestingly, some of these plants can have female, male, and bisexual flowers – this is referred to as trimonoecism and an excellent example is the horse chestnut.

A good example of plants with both male and bisexual flowers is the hellebore, while plants of the Compositae family, as well as catchfly, are good examples of plants with both female and bisexual flowers.

In some plant species, we may have trioecism – here, the female, male, and bisexual flowers may be on different plants. An excellent example is grape and ash.


Wrapping It Up

Knowing the difference between monoecious, dioecious, and polygamous plants and how to use them is an amazing party trick. But that’s not all! It also helps you make better choices when planning your garden or landscape.


Last Modified: June 1, 2022