10 Ginkgo (Ginkgo Genus)

As Dutch elm disease unwound its unstoppable decimation, city foresters began to slowly replace the fallen giants. No longer did great, graceful limbs reach toward one another from across the streets to create shady archways for my own, growing limbs to walk or bicycle beneath as a child. Just as with the emerald ash borer epidemic, they sought replacements for the destroyed elms, including new cultivars resistant to Dutch elm disease. These new kids on the block brought along with them hardy dispositions with combinations of pest, salt and sulphur resistance, and a touch of drought tolerance thrown in for good measure.

Subsequently, the boulevard across from my parents’ house acquired several such newcomers along its length. Maples, northern catalpas, honey locusts, Kentucky coffeetrees and ginkgos began to appear in well-chosen variety packs around the city. When my dad discovered two ginkgos planted on the parkway boulevard right in front of their house, he was overjoyed. My enthusiasm for ginkgos arose, most likely, from this contagion of his rubbing off on me, besides the fact that they are truly fascinating. My daughter says the same thing when describing his animated introduction to her of the two ginkgos on the parkway and explaining all about them.

“I was amazed,” she told me, “to learn from Grandpa that trees can be separately male and female, just like people!”

Frankly, I was equally astonished when I learned this as an adult! Many trees greet us as either male or female, such as ash, willow, junipers, and mulberries (to name a few). In botany, trees such as these with male and female reproductive parts occurring on separate trees are termed ‘dioecious’ (from Latin, two homes). Other trees do things the monoecious way (L., one home), such as oaks, pines, and birches. Monoecious trees locate their female and male parts on separate branches of the same tree. Things get trickier from here, though. Hermaphrodite trees, such as linden, apple, hackberry and elm trees have both male and female parts (stamen and pistil) present in the same flower, called ‘bisexual’ flowers, or ‘perfect’ flowers. Taking this further, both unisexual and bisexual flowers can be present in combinations on some monoecious trees, and sometimes within the same flower cluster, such as with the Ohio buckeye where the upper flowers are primarily staminate (male) and the lower flowers are primarily perfect (both male and female). Then there is gender swapping, further blurring things in the tree world. For example, the striped maple tree (Acer penslvanicum) changes sex repeatedly, sometimes year to year depending on various factors (age, health, and environmental conditions).

Ginkgo is dioecious. Separate male and female trees rely on wind to pollinate between them in the spring. Male catkin-like ‘cones’ release multitudes of pollen in the spring. Female ovules hang open to the air for pollination, producing a pollination droplet on each tip specifically made for a male gametophyte to land on and start the long fertilization process.  But wait! All this is actually conifer-like behavior! Yet, on first glance, ginkgo resembles any other deciduous tree with new leaves emerging in the spring and colorful fall foliage shedding in autumn. That is where the resemblance ends. Most deciduous trees are angiosperms, meaning they have proper flowers producing seeds within a protective ovary. Ginkgo trees do not have this. Their lineage goes back to millions of years before the flowering trees to a landscape that included conifers and cycads. These first seed-bearing trees are categorized as gymnosperms (literally, ‘naked seeds’). Their ovules are open to the air for pollination, not protected within flowers. Even ginkgo’s vascular system within the inner wood resembles that of conifers, adding to the seemingly contradictory but useful, general description of ginkgo as a ‘deciduous conifer’. That said, ginkgos are not strictly conifers. They evolved alongside conifers and cycads millions of years before angiosperms appeared on the scene.

The remaining Ginkgo biloba we are lucky enough to have still with us today —  looking remarkably the same as its fossil record tens of millions of years ago — is the sole survivor and only member of its order, family and genus. Having survived millions of years on Earth while all their close relations across the planet became extinct may help explain how a species that predates the dinosaurs has its own way of doing things – and that way certainly works! So, what is exactly going on in the deeper ginkgo world? Clearly, it’s a lot more than meets the eye! One very dramatic trait that sets ginkgo apart from both deciduous trees and conifers, is the ginkgo pollen grain’s germination of swimming sperm. In the seed-bearing trees, this feature is shared only with the cycads. This trait dates back to Earth’s oldest lineages of seedless, nonflowering plants whose ancestors first evolved in water — ancient plants that include the ferns, mosses, algae and horsetails.

Ginkgo biloba is often called a ‘living fossil’ because in comparing fossils to their counterparts in modern ginkgos, essentially no structural change is apparent. Just as they always have done for the last 200 million years or so, the leaf veins fork into a “Y” pattern by twos from a common point fanning out with no main vein connecting them (called ‘open dichotomous venation’). This open veining system is relatively primitive compared to the way deciduous leaves formed in subsequent periods, and no other temperate, woody plants shares this. I’m glad! I love watching those charmingly distinctive ginkgo leaves flutter daintily along the branches like little hands waving or butterfly wings or fans. Ginkgo leaves have another distinctive trait. They take two forms depending on if leaves emerge in spring from the short spur-like shoots that run along the branches, or if they emerge later in the season on long shoots. Short spur leaves are more intact, while leaves growing on the longer spurs have an indent in the center of the fan creating two lobes — this is where the biloba species name derives. Even the way ginkgos go about dropping their leaves in autumn is unique. Instead of letting go of a few leaves at a time over days like other deciduous trees, ginkgo drops its brilliant yellow leaves all at once over hours or overnight.

Researchers studying the fossil record have determined that many species of Ginkgo began to die out during the Pleistocene period’s glaciation occurrences at the time of the Ice Ages. The one species that survived (Ginkgo biloba of today), retreated from a rather wide range throughout what is now Asia to remnant forest enclaves in what is now China where they still grow today to a certain extent in the wild. Ginkgo’s continued survival was more recently further ensured through cultivation first in China, then through trade routes from China into Korea and Japan around the 13th or 14^th century. Lovingly expanding on this, Japanese horticulturists carefully transplanted ginkgos across their nation. Like the revered linden or lime trees of Europe, ginkgos become beloved it seems wherever they are gifted, grown or transplanted, and are now enjoyed in urban streetscapes across the world – including my dad’s boulevard across the street where they invoke delight in any language.

One remarkable trait contributing to ginkgo’s hardiness is their robust immune system. Individuals can easily live 1,000 years and more, especially when protected in such areas as temple gardens over centuries, and as long as they are growing in the temperate climate they love with the right water conditions. In addition to their strong immunity, ginkgos also have a stocked toolbox of reproductive survival strategies that have contributed to their seemingly unstoppable resilience. Peter Crane’s marvelous book titled, Ginkgo: the Tree that Time Forgot, describes one of the more sensational tools ginkgo possesses as embedded buds hidden within the axils of each leaf. These buds become buried in the wood over time as the tree grows, but are potentially always at the ready to kick in and emerge when faced with complete devastation, such as a tree losing all its limbs. Some very old ginkgos can produce downward growth from these hidden buds to ground level, growing new trunks, branches and roots, essentially ensuring that the ginkgo tree reproduces itself. New growth can sprout downward from the buds that remain from the very first leaves the ginkgo tree formed as a seedling, buried deep within the tree’s base. These can sometimes form lignotubers downward into the soil as well. Juxtaposed against such seeming immortality, I feel grateful for the companionship ginkgos offer as quiet ambassadors of renewal and ongoing life. Ginkgos endure, perhaps not quite so timelessly as the light, air and water that feed them, but they do give the effect of coming pretty close!

When Susan Jane and I arrive at the ginkgo grove, I show her the large male I would like to tag. It overlooks the street and is not near any walking path, but it does lead to other tagged trees in a coherent sequence for the walking tour.

“Yes, this is a beauty,” she assents, reading the sign before giving it to me to attach. “I see that ‘cone’, ‘conifer’ and ‘deciduous’ are all used in the text for this. Interesting…because deciduous trees don’t have cones, right?”

“Right,” I reply, “except for ginkgos! Male ginkgos produce pollen cones, and females produce ovules that will become the seeds. When they ripen, they’re apricot colored and fleshy like fruit, but that’s just the seed’s soft outer coating. Female juniper cones look like fruit, too, like berries, but they’re not berries either.”

We step back a moment and look at the rich, green leaves of the male above us. The neighboring tree is female, so we step that way to look for her hanging ovules.

“There’s some,” Susan Jane points.

A few round shapes are visible peeking out among the leaves. They are still green and hang mostly in bundles of 2 on one inch stems.

“Soon these will fall off the tree and cover the ground beneath. I think they’re really pretty lying there among the leaves. At that point, the newly-formed embryos will continue to grow and develop as they lie there on the ground.”

“At that point they also stink,” she said.

“Yes, some people do say that” I agreed, smiling. “Especially when that fleshy outer part starts rotting away. Before that, they look pretty tempting to eat!”

“Really!?”

“Yes,” I say, a bit embarrassed to tell my story, but decide to continue. “Last October, my mom and I were walking here collecting leaves. The ginkgo seeds looking so pretty on the ground intrigued me, not knowing much about them, so I took some home in my pocket and put them in a bowl for decoration.”

“Oh no!” Susan Jane says, “your mom has dementia and ate some, right?”

“Yes,” I say ruefully, and go on to tell her the story. “I heard my mom say from the other room, ‘My mouth is burning! ‘What could be causing that?’ I called back to her from the living room, ‘What?! Did you eat something?’ My mom said, ‘I don’t remember! ‘What did I eat? My mouth and throat are burning!’ What, indeed!? Ginkgo biloba fruits are what she ate! While she was busy at the bowl, I was just learning from my resource that ginkgos are not exactly edible. It also informed me that they are foul smelling because the flesh around the seed contains butyric acid which gives the seeds their rancid or rotten odor, like vomit. They didn’t exactly strike me that way, though. The odor from the ones I picked up was definitely pungent, not terrible, but strong enough that I washed my hands after handling them — which is a good thing to do after collecting them.”

“Why is that?” Susan Jane asks.

“Well, yeah, you see, it got worse as I read on, because the pulp can cause an allergic skin reaction similar to poison ivy and can be irritating to mucous membranes. Hence, why my mom now felt burning in her mouth and throat. She most certainly must have popped one of those into her mouth and eaten the soft outer part. The inner seed inside the flesh is also considered mildly toxic, apparently nutritious to eat in moderation. The seeds without the outer flesh are roasted and sold as ‘ginkgo nuts’. The nuts have been used forever in Asian cuisine. Every autumn I see people gathering the seeds in the park. But you do have to roast or cook them before eating, never eat them raw, because the heat neutralizes some, not all, of the toxins.”

Susan Jane nods, taking all this in.

“Wow!”

“Ironically,” I add, “western medicine uses an extract made from the leaves touted as helpful for improving memory and cognition!”

“Yes,  it is ironic for your mom,” she chuckles, “but what happened with her after? Was she okay?”

“Oh, in an hour or so the burning retreated to only her mouth, and in 2 hours it was only her tongue, the sensation completely gone by bedtime. The next morning there were no aftereffects at all.”

“Good thing!”

“Agreed!”

We continue walking across the street (as it happens towards the red pine next) but I am thoughtful as we depart this life-affirming tree that I so love.

Early in the morning of August 6, 1945, Hiroshima’s ginkgo trees were happily growing when the A-bomb dropped on the city, incinerating everything in its wake including trees. Growing more or less 1 mile from the epicenter of the blast, one particular ginkgo tree had its trunk destroyed, but sprouted new leaves again from the roots around its base the following spring. This tree and other tree species very near ground zero that came back from near annihilation became known as survivor trees (hibakujumoku, in Japanese) and are honored today with memorial plaques. They are remarkable symbols of the eternal cycle of growth and renewal. They are ambassadors of enduring hope.

My dad’s last breaths took place in the upstairs bedroom of the house that had been his home for 50 plus years. Two ginkgos grow on the boulevard just outside where the room overlooks. Their leaves had already turned brilliant yellow weeks earlier, and then had chosen their time to create a seemingly instant carpet of fallen leaves beneath as is the way with ginkgos. Maple leaves had also fallen, as had the leaves of the little-leaf linden on the front lawn. I was with him in the room when his eyes opened wide suddenly and looked into mine. His head came up off the pillow. I thought he had something to say, but he didn’t, only looked at me with a wondrous releasing of light from within and out of his eyes exactly like the luminous sky, vast, wide and wholly filled, and into which that light released.

I have found another thing that endures – the wind — the same thing as my breath, pulling inside to every capillary crevice oxygen into my heart. And therein lies another abiding thing. Love. Fanned to life with breath and air. Awake, aware, love needs no improvement, no upgrade, no change. It is its own creative life force, sufficient and enough. On immutable wings it floats, simple and free, upon streams of sunlight into everything.

The body is a temporary thing. That is a given. Eventually, it gets left behind, is no longer needed to enjoy the view. When that time comes, we need only use it for one last hike, climbing the mountain as high up as possible before stepping into air the color of azure blue. In my imagination, I make this ascent as far as I can go until I meet the place where rock meets sky. Beyond that, I cannot step, at least not yet, not before my own time comes. Instead, I sit in quiet contemplation, perched up there on my mountain top as my mind’s eye watches sunlight sinking into dusk. My gaze sinks into the valley below where pinpricks of light from the houses blink back up at me into the night sky far away to the horizon. The twinkling scene lifts across the hills like sparkling glints of a million eyes reflecting back the universe of stars above in the glance of a million others.

“Godspeed!” I whisper into that soothing darkness — inadvertently getting Susan Jane’s attention as we finish crossing the street.