Smelly ginkgo seeds are a curiosity and a problem.
A week ago today, I brought my morning coffee to the computer and sat down to read the news. One website led to another, and before long, I was taking a look at Google's Hot Trends -- a list of the top 40 search terms of the past few hours.
Usually when I glance through the Hot Trends, I don't know what or whom most of them are. (I don't keep up very well with "popular culture", as my son calls it.) So, I was surprised to see a familiar name on the list -- "gingko tree". Yes, the tree Ginkgo biloba was one of the top 40 Hot Trends of that moment.
Why did the curiosity of thousands of internet users focus on the gingko tree at about 7:00-8:00 A.M. PDT on October 5, 2009? I think I can guess. Two headlines from Google's list of ginkgo-related news articles and blog posts offer a clue:
The seeds are about the size and color of wild yellow plums. The odor of the fleshy part of the seed is often compared to rancid butter (both contain butanoic acid) or to feces.
Technically, the ginkgo tree's seeds are not fruits. The gingko is classified as a gymnosperm because it produces naked seeds. The squishy, smelly part of the seed is a fleshy shell that covers the harder life-containing center of the seed.
A standard solution for the seed problem has been to plant male ginkgoes. Male trees produce pollen-bearing cones. It is interesting that the pollen contains motile sperm (sperm that can move themselves). The sperm fertilize ovules on the branches of female trees. Fertilized ovules develop into seeds.
It is unusual for gymnosperms to be dioecious-- that is, to have separate male and female plants as the ginkgo does. Ginkgos have a latent ability to be monoecious: male ginkgoes sometimes start producing seeds, foiling the best-laid schemes of landscapers and homeowners.
Various (male) cultivars have been developed and are available through nurseries. Or, you can grow your own ginkgo tree from seed. But please don't plant ginkgoes where the seeds will ever be a problem -- even if you're starting with a male tree. Plant them in a place where you can see and enjoy the unique beauty of the tree -- but a place where you won't smell or step on the seeds, if the tree ever produces them.
I love seeing ginkgo trees in the fall. The leaves usually become a very true shade of yellow.
ReplyDeleteAs you know, I don't often write about non-native species of trees, but I made an exception to the rule for ginkgoes because I like them. :)
One possible side effect in urban areas of planting only male trees to avoid the mess and stench of fruit, has been a major increase in pollen, causing more torment for allergy sufferers.
ReplyDelete"Male cones ripen to release pollen when female flowers are receptive – usually in March to early April. Ginkgo pollen is a light, buoyant spindle shape when released. Ginkgo pollen can generate a number of allergy problems during the short time it is on the wind. "
ReplyDeleteSource: "Identification & Silvics of Ginkgo", Dr. Kim D. Coder, School of Forest Resources University of Georgia