Which trees are dioecious

When planting trees, not appreciating different tree genders can lead to many unwanted problems. Female flowers and female trees produce fruit and seeds. Male flowers and trees produce pollen. Making the correct choice of tree gender can be important. Anyone who has ever smelled putrid ginkgo fruit, washed mulberries off their car or sneezed at tree pollen should understand.

Sexual reproduction in trees allows male genetic components pollen to reach female components of the same species, grow to fertilize an egg and produce a viable embryo within a seed. This fertilization process is made possible by flowers or cones. The type of flowers or cones a tree produces determines tree gender. Tree flowers can have male parts, female parts, both male and female parts together, or none at all.

Some of these parts may or may not be functional. You cannot tell flower function or gender just by looking. Trees do not show their gender until they are sexually mature and start to flower.

Sexual maturity in trees, depending upon the species, can occur from 1 to 50 years of age. Sometimes sexual maturity occurs for either the male or female flowers and cones.

For example, young hardwood trees just becoming mature tend to generate male flowers first, and then eventually generate female flowers. The opposite pattern occurs in some young conifer trees. Female flowers bear seeds or fruits. You may purchase male clones to avoid picking up messy seed pods or capsules in the fall.

If you are allergic to certain tree pollens, avoid planting dioecious male trees. Most popular of dioecious landscape shrubs are the hollies Ilex spp. Gardeners may select female plants for their colorful fruits in fall and winter.

Holly fruits may be red, yellow or white colored depending on the cultivar. Be certain that the correct pollinating variety has been planted nearby the specific female cultivar s. Over the years male clones of several landscape trees have come to dominate our yards and gardens.

Male fruitless types do not litter the ground with messy pulpy fruits and seed pods. Male mulberry tree pollen flowers. Female mulberry tree with fruit. Different species of plants produce different amounts of pollen. Some very beautiful, showy, fragrant flowering plants produce very little pollen per flower. With a dioecious plant it is the other way around The "reason" that dioecious male trees or shrubs need to produce so much pollen is again More pollen is produced, it is smaller, lighter, shaped to float better They've been exposed year after year, and before them, so were their parents, their grandparents.

Instead of getting used to it, instead of becoming immune to this kind of pollen, it has worked just the opposite. Allergies arise, always, from repeated over-exposure over time to a possible allergen. Each word is key here So, all of us have been exposed to this pollen from the dioecious males For the reasons outlined above, it is crucial that we do not include many, if any, male selections in our landscapes