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Do Trees Have Genders?

Do trees have genders? Certainly, though the question is more complex than whether a tree is a male or female tree.

When thinking about your neighborhood trees, you may not have thought of them as gendered. However, if you have a fruit tree, it might be good to know whether you have a male or female tree so you can prepare for a potential harvest of fruit or berries. Having that information could be useful if you’ve, for instance, moved into a new home and you haven’t experienced a full season-cycle. At the very least, you can prepare yourself for allergy season or for harvest in the fall.

Whether you’re interested in your trees for the fruits, or if you’re just curious, here are three facts about a tree’s gender.

1. How Can You Tell What Gender a Tree Is?

Really, the only way is to wait until spring to see them bloom. Sometimes a tree will be all-female, and sometimes it will be all-male. This type of tree is a dioecious tree—all the flowers are of one or another gender. However, often there will be both male and female parts to the flowers on the tree, which makes it a monoecious tree.

If your tree loses its leaves each fall, the easiest way to tell gender is to look at the blossoms. (We’ll get to evergreens in a minute.) When you look at the tree’s blooming flowers, you can see the male reproductive parts as the stamen, which is where the pollen is stored. The female part is the egg-holding pistils. This is the part, once fertilized, that will grow into a fruit.

In other cases, the difficult part of figuring out the gender of the tree is whether the tree has all female or all male flowers. A tree with only male blossoms will have pollen and will not grow any fruit. A tree with only female blossoms doesn’t generate any pollen and will only grow fruit. Therefore, if you have a female cherry tree in your front yard but no male cherry tree near enough to pollinate it—with the help of the average bee or bird or other pollinating species—you won’t have any cherries. Your female cherry tree will definitely show off her beautiful blossoms in the springtime, though!

On the flip side, a male cherry tree might be the reason why you suffer allergies in the springtime. Pollen is what irritates our skin, makes us sneeze, and gives us itchy, runny eyes and noses.

2. What About the Genders of Evergreen Trees, Which Don’t Bloom? How Can You Tell?

The gender of an evergreen tree is all in the pinecones. An eastern white pine, for example, can create a pinecone that has both the pollen and the seeds. However, a tree doesn’t want to self-fertilize since that doesn’t make the gene pool any stronger. Self-fertilizing will eventually make the whole forest weaker, so nature has found a way to make that more difficult. This includes putting the pollen and the seed on opposite ends of the pinecone. Once a pinecone has been fertilized (hopefully from another tree), the seed inside the pinecone matures, and at the right time, it opens up and the seeds spray everywhere.

Not only will evergreens drop their pinecones, but animals will pick them up and move them around, further widening the potential pollinators in the area. Squirrels are especially good at taking pinecones further afield. Even if they eat all the seeds out of the pinecone, the pollen will have been taken somewhere else, where it might be useful. And squirrels will frequently stash pinecones and other nuts, intending to come back to them, only to forget them. Once the seed matures, a buried stash can become a nursery for a new tree.

Evergreens are among the oldest plants in the world, and they’ve hardly changed this method of reproducing in all that time. Scientists have found that conifers have been around for about 280 million years. Much like early crocodiles and sharks, nature found something that worked and stuck with it. One way evergreens have evolved over time, especially in dry areas where there are frequent wildfires, is that fire signals to the pinecones to open so that the trees can start propagating again.

Coniferous trees tend to burn faster because they grow closer together, are full of sap, and their fallen needles on the forest floor are excellent fuel for a wildfire. Once the wildfire has passed, though, an evergreen forest can spring up again very quickly because all those pinecones on the ground are now open.

3. Can Trees Switch from One Gender to Another?

Some trees can! It turns out that gender and sexuality can be more fluid when it comes to plants. If there are too many of one gender in an area, some trees (and other animals, such as clownfish and green frogs) have evolved the ability to change in order to better balance the ratio of male to female. It should be noted, though, that a tree cannot change from male to female and back again. Usually, when a change like this occurs, it’s from male to female.

One such tree is the striped maple. You won’t find one in Oregon—they’re native to the Adirondack Mountains. Some botanists have found that a sex change will often happen when the tree is undergoing or has experienced trauma. This could be as little as deer chewing on their bark or rubbing their antlers on them. The tree then figures that if it’s going to die anyway, then it would be best to be female and spread its seeds around to guarantee the survival of the species. Of course, this doesn’t always result in the entire tree changing its gender. A broken-off branch could become either all-female or support male and female blossoms, even if the whole tree remains male.

If you’re having difficulty identifying tree genders, a certified arborist with Mr. Tree can certainly come to help you out. Contact us today to schedule an appointment with one of our knowledgeable and friendly arborists.