Monoecious and Dioecious Trees – What’s the difference?

We often use the terms ‘Dioecious’ and ‘Monoecious’ when talking about the reproduction of trees/plants. 

Here are the basic definitions applied to trees: 

• Monoecious: Species that have separate male and female flowers on the same tree. 
• Dioecious: Species that have male and female flowers on different trees. 

Monoecious Trees

Monoecious trees can produce flowers and set seed on their own, without the need for another individual pollinator. Most tree species are monoecious. 

Some monoecious trees include

• English Oak (Quercus robur)
• Hazel (Corrylus avellana)
• Hornbeam (Carpinus betulus)

Male and female Hazel flowers (Corylus avellana)

Close up of a male Hazel flower (Corylus avellana)

Dioecious Trees

Dioecious trees require another tree with a flower of the opposite sex in order to pollinate. It is quite rare for trees to be dioecious.

Some dioecious trees include:

• Ash (Fraxinus excelsior)
• Yew (Taxus baccata)
• White poplar (Populus alba)

Male White poplar catkin (populus alba)

Female White poplar catkin (populus alba)

But how do you tell whether your tree is dioecious or monoecious?

It can be quite hard to tell the difference but the telling factor in defining whether a tree is monoecious or dioecious is whether there are both male and female flowers, or only one sex of flower on it:

• Male flowers have a stamen that contains pollen (looks like it has small filaments) 
• Female flowers have a stigma which receives pollen