Acrocarpus fraxinifolius, a tree for the future

- It turns the Armillaria mellea fungus into mycorrhiza and lives with it in symbiosis.

- Active ancestral genes in its genome and become resistant to the cold.

I want to tell you the history of an extraordinary tree that, being tropical strict and evergreen, activated several ancestral genes that it had blocked in its genome perhaps million years ago and it transformed itself into a non-evergreen tree, entering hibernation in the coldest months of the winter of Majorca to be able to arrive until the spring without undergoing the freezing of its branches. At some time of its evolution on the Earth it was able to surpass a time of intense cold with adaptive mutations, that recorded an indelible memory in their genome in the form of several genes of resistance to the low temperatures, which later stopped being useful to it when changing the climate and to be made warmer again. 

 

 Mundani tree, Acrocarpus fraxinifolius, born in the spring of 1987. In the photograph was 16 years and was about 14 meters. Today is 24 years old and about 20 meters high.

The genes that made to it resistant to the cold did not disappear but they remained blocked, slept, inactivated in its genome until forced by the low temperatures of the winter of Majorca unblocked them to survive.

In Christmas of 1986 a pair of friendly just married, Toni and Avelina, traveled to honeymoon Kenya. Before starting off they asked me if I wanted something of Africa and I said to them: "seeds of trees". They brought me a pile of Kenyan fruits: cases of the chorale tree of South Africa, Erythrina caffra, a great fruit of baobab full of seeds, Adansonia digitata, a heavy one and extended fruit of the tree of sausages, Kigelia aethiopica, several capsules of the euphorbiaceae of savannah Croton dichogamus, a pair of fruits of the passion, Passiflora edulis and the cases of a legume not known whose seeds I seeded immediately thinking that one was an acacia.

 Seeds of Acrocarpus fraxinifolius.

A single seed germinated and from it a little tree of great pennate leaves was born that remained almost without growing during four years. Something prevented its growth and I managed to activate it neither with installments nor with compost. In the spring of year 1991 in my garden a lime tree died, Citrus aurantifolia, in the same place where before already several trees had died, because the earth was invaded by the mycelium of the Armillaria mellea fungus that attacked the roots of any tree I finished as soon as it seeding and in few months it died thundered against. No longer I dared to seed nothing in that one infected place.

Small mundani tree of two months of age. 

A day watching the tropical small tree that did not grow happened the idea to me to seed it in the contaminated area by the fungus, because I thought that in any case it would end up dying in the flowerpot. It was the best thing than I could do by it. To the few days it underwent a spectacular change, its apical yolk began to grow at an incredible speed and at the beginning of the autumn of that one same year it measured more than three meters. It could not believe to me. I seeded when it did not surpass the 15 centimeters, it had the yellowish and withered leaves and gave the impression that one was dying. What had happened? , What thing had built the miracle?

Now after more than 20 years I think to already have the answer to these questions. As many forest arboriculturists know the Armillaria mellea fungus, although generally it behaves like a assassin when invading and to rot the roots of the sensible trees, with some forest species also is possible to be tolerated like a fungal symbiont with the mycorrhiza functions, so that instead of to kill a very beneficial association for both, that is to say, a symbiosis forms them among them. And this was indeed what it happened to it to the small dying little tree. In the hole that I dug to seed there were it still pieces by roots of the trees that had died there. They were in favor white of the mycelium of the fungus and the earth smelled of rotting, the typical pungent scent of the Armillaria mellea. Knowledgeable of the uselessness of any measurement to eradicate this plague, I did not bother myself nor I would follow in clearing the pieces by rotten roots. 

 Mushrooms of Armillaria mellea.

For some reason that I do not know to the mycelium of the fungus fell likeable the Kenyan small tree, it surrounded its weak roots in a white hug of life and began to provide it water and minerals. When the apical yolk initiated the growth and the first leaves were open, the small tree gave back the favor to the fungus and it provided it in return carbohydrates synthesized by the leaves through the photosynthesis. One had begun a marriage of convenience that allowed the small tree to become two decades in an imposing tree with a thickness of the trunk of more than 30 centimeters and one height superior to the 19 meters. 

After 10 years still I did not know the identity of the Kenyan tree, thought that one was an African acacia and it did not manage to give with its name. A day I entered the forum of plants of Infojardin, put several photos of my supposed acacia and the prestigious specialistic botanist in tropical trees D. José Manuel Sánchez de Lorenzo-Cáceres in few minutes it gave me the answer: Acrocarpus fraxinifolius, a leguminous arboreal one original of India, Burma, Thailand, Indonesia and Malaysia, that in their original habitat form leaves from the ebullient tropical forests of these countries and reaches the 50 meters of height. Finally already I could give a name to the highest, exotic and spectacular tree of my garden.

 Photography of the terraces of my garden in the spring of the year 2006 in which we can see the mundani tree in center of the image with its showy red sprouting after the hibernation. (I recommend to extend the photo with a double click to see better the details)

This leguminous forest one receives different names according to the country where it grows or it is cultivated. In India they call MUNDANI, in Australia and in tropical Africa where they are had made great plantations they call PINK CEDAR and in Latin America where also it has been introduced with great success as forest species calls CEDRO ROSADO, MUNDANI or LAZCAR. This last name the Mexicans put it in honor to president Lazaro Cardenas, great impeller of the culture of this Asian tree. Locally it receives other many names, but the most known they are those than I have mentioned.

It does about ten years it occurred a great snowfall in November, the snow was accumulated on the crown of the mundani tree that still conserved the leaves and the weight tore a branch of about 4 centimeters in thickness. Instead of to throw it to the pile of firewood to burn, I trimmed it the most tender end, I left it without leaves and I deeply nailed it in the ground next to a plot wall that watches the south where I finished talking an Eucalyptus gunnii dead fulminant by the attack of the Armillaria mellea fungus. Previously a Mediterranean savin, Juniperus phoenicea subsp. turbinata, was there same dead. They spent the months, the branch finished hidden between the grass and I forgot her.

A day of spring, much later, I happened near the wall where the branch of mundani tree was nailed and red leaves that excelled over the grass drew attention to me. I approached and my surprise was capital. It was the branch that had appeared after 22 months. I believe I could not. It was like a miracle, because the leguminous stakes of the arboreal ones usually are very obstinate to take root and this one not only had taken roots and had appeared, had done but also that it in a ground infested by the mycelium of the killer fungus. Again it was demonstrated to the symbiosis between the roots of mundani tree and the mycelium of the Armillaria mellea. At the moment the taken root branch has become a beautiful tree of about 7 meters, healthy and vigorous. The fungus already has everything what needs to live and since then has respected to all the trees and shrubs that there are next to mundani tree: a Tilia cordata, a Feijoa sellowiana, a Brachichiton populneum, two Livistona chinensis, several Citrus sinensis, an Anagyris foetida, an Agave attenuata, a Buxus balearica and a Buxus sempervirens.

Taken root stake of Acrocarpus fraxinifolius.

Years later I tried to make an aerial layer to a branch of mundani tree but after 12 months it followed without taking roots. Tired I cut to hope it, I smeared the base to it with rooting hormones and I seeded it in a flowerpot. About six months later it brought forth a yolk in the low part of the stake. Although at the outset it seemed to grow well, soon was suspended. It was several months without growing, like paralyzed. I did not understand which was the reason.

It agreed then that the Armillaria mellea fungus killed of sudden form my unique masculine unit of plum tree of South Africa, Harpephyllum caffrum. After taking it by root and burning it, it happened oneself to me to seed in its place the stake of mundani tree that did not grow. By third time the miracle took place and the second clonic son of the Acrocarpus fraxinifolius been born from a Kenyan seed began to vigorously bring forth and in few months transformed in a beautiful small tree. Again it was demonstrated the symbiosis by the roots of mundani tree with the mycelium of the fungus that so many trees, shrubs and lianas has killed to me in the 22 years that I have the garden.

Bud of the stake taken root after three months of seedtime.

Same clonic mundani tree one year later at the height of summer.

 Clonic father of the previous tree appearing vigorously at the end of March after successful surpassing the long months of the Majorcan winter with several frosts of until -2ºC. 

Inflorescences in swab of the previous Acrocarpus fraxinifolius with the buds of new leaves of an intense red color blood by its wealth in anthocyanin.

Photography of the previous inflorescences done with zoom lens by high altitude of the branches of mundani tree.

 

First fraxinifolius Acrocarpus mature pods at 25 years of age. (This photo and the next three, along with the accompanying text, I've added 10 months after publishing this article).

For over 10 years my tree Mundani flowers every spring, but never any fruit curd. I thought the cause was the absence of natural pollinators. The month of April 2012 my Mundani had a spectacular bloom, was completely covered with flowers. It was gorgeous, which was not lost on a tiny little birds that came every evening to sip greedy the abundant nectar from flowers. Finally I knew Acrocarpus fraxinifolius flowers in tropical forests of their home countries are pollinated by birds. In Mallorca live of course not the same Asian tropical birds, but two Mediterranean species discovered nectar from my tree Mundani and have become their surrogate pollinators: Sylvia atricapilla and Parus major. Not rule out that other species of birds have visited the flowers. Over the years I will discover, with the help of my ornithologists friends I go identifying.

This bird, Sylvia atricapilla, came every evening to sip the flowers just opening.


Fraxinifolius Acrocarpus mature pod collection in September 2012.


Anterior sheath open showing seeds inside.


Detail of the first ripe seeds of my Mundani tree.

The seeds of the Acrocarpus fraxinifolius have a thickness impermeable cutícle that makes difficult much to its germination when preventing the hydration of the embryo, taking up sometimes to 4 years in germinating. In order to accelerate the process in the great Australian, African and American loggings they put under the seeds a sulfuric acid bath that scarified chemically cutícle and makes permeable to the entrance of the water so that the embryo hydrates itself.

Another effective and cheap, although still more laborious method, consists of making a small notch in the cleared part of each seed with nail clippers or a small knife. 

Seeds of mundani tree with a small notch in the cleared part done with nail clippers.

Soon the seeds submerge in temperate water during 24 hours. Cotyledons and the embryo are hydrated quickly and tripled their size.

Submerged seeds in water of the previous photography. 

Seeds already hydrated after 24 hours in soaking. 

This way one even uses excessive respect much to its germination, happening of several months or several years to only one week. Soon they are seeded in shaded flowerpots to a constant temperature of about 20 - 25ºC.

Seed of Acrocarpus fraxinifolius being born to the 4 days of seedtime. 

 Small mundani tree just been born. In cotyledons is appraised  the scar of the notch done with nail clippers.

Like the mango and the cashew, the Acrocarpus fraxinifolius better propear in tropical and subtropical climates with a dry station and a humid station. Their pivoting roots penetrate deeply in the ground where they find the humidity necessary to support without problems the months of drought. In very favorable conditions its growth is spectacular getting to grow up to 8 meters in a single year. In the plantations of the tropical countries it is possible to be cut to the 10 years of seedtime, since to this age its trunk reaches a considerable thickness and a height. Once cut one second wood harvest sprouts again thus with facility from the base, obtaining itself to the 10 years. Their roots fix nitrogen atmospheric, so that its culture enriches the earth and favors the good development of the surrounding trees. The trunk is straight and without ribbings. It does not need to be pruned, since self pruning of natural way, falling by themselves the inferior branches. It is resistant to the majority of plagues. By own experience I have observed that the phytophagouss insects do not attack it. 

Base of the trunk of mundani tree to the 24 years of age. See as the main roots excel outside the Earth and gives the aspect him of a heron leg. 

The Acrocarpus fraxinifolius is because a tree for the future. In the next decades the plantations of this leguminous arboreal one will cover great extensions in all the countries with favorable climates, will contribute the wood necessary to cover great part with the demand of the lumber markets and will allow to preserve the forests of the indiscriminate cutting, saving of the extinction to thousands of animal and vegetal species.