Cindy Haynes of the Department of Horticulture at Iowa State University explains that the main difference between dioecious and monoecious plants is that dioecious plants have male and female flowers on different plants, while monoecious plants have male and female flowers on the same plant. This basically means that dioecious plants only bear flowers with a single gender’s reproductive organs.
On the other hand, as Haynes explains, monoecious plants have their stamen and pistil in separate flowers on the same plant. The two types of plants differ in the arrangements of the male and female reproductive organs based on the distribution of these organs on the plant.
Oak Leaf Gardening states that dioecious plants are either male or female. It is necessary to have male and female plants in close proximity for reproduction. Male plants only have male flowers, and female plants only have female flowers. Examples of dioecious plants are holly and asparagus. Holly plants need a male and female plant in close proximity, because only the female plants have the ability to produce fruit. David Beaulieu of About Landscaping explains that there must be at least one male plant growing nearby so the fruit-bearing female plants will be pollinated.
As Oak Leaf Gardening explains, monoecious plants typically rely on the wind for pollination to allow the male pollen to reach the female flowers. A monoecious plant usually houses different flowers, some being male and others female. Examples of monoecious plants are squash and the common hazel Cornus avellana.