Sunday 22 March 2009

Sex and the Sycamores

While you may not be able to grow sycamores or ginkos in your garden, some understanding of the complexities of tree gender expression may help to avoid messy problems in your yard.

I used to enjoy visiting a friend's verdant garden in Brentwood. She would walk around pointing out the new trees and shrubs assigning genders more or less randomly. “ That viburnum she's not happy, he's shading her out” and then my hostess would point up to the large box elder that towered over the viburnum. Judging by the seeds on the box elder I knew this wasn't entirely true. When in this situation there is much to be learned by simply listening. After a few visits I discovered that more than assigning genders, my host was personifying the trees as they were literally part of her family.

Trees express gender in a variety of ways. Typically genders are assigned by the presences of male or female flowers. Male flowers produce pollen and female flowers produce seeds. If it were that simple this would be a very short article.

Flowers on trees and shrubs can be male, female or both. In which cases the plant would be better referred to as an “It”. To further complicate matters some species of trees have individuals with only male flowers, clearly “He” trees. The same species will have trees with only female flowers, clearly “ She” trees. This same species will have a small percentage of trees that have male and female flowers on the same individuals, clearly “It” trees. Given that this may account for up to 15% of the individuals of the species it is clearly not a random mutation, rather a part of the overall genetics of the species.

While this may be a surprise, you won't have to go far to find these strange exotic trees.

Ash trees, maples, and yes sycamores all have this type of gender expression. It can be a nuisance and even an major problem if you have a seed bearing tree in an area where the seeds are not welcome. Some trees, like crab apples can be down right dangerous when they are to close to walks or patios. Slipping and falling on decomposing apples can be more painfully than getting stung by a wasp disturbed from its apple sauce dinner. If you have ever had the misfortune of stepping on the ripe fruit of a ginko tree

you will remember the pungent odor. Fortunately plant breeders have used their knowledge of plant anatomy to develop varieties that are based on male cultivars.

This ensures that you have the landscape tree you want without the seeds that may cause trouble. “Baron” maple is a good example of a seedless male cultivar of Box elder.

If you are planning on planting trees this spring, consult your certified arborist they will help insure you get the best tree for your location.

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