Raising Alsophila spinulosa as a potted plant? Beware of life in prison

If you walk into the greenhouse of Wuhan Botanical Garden, you will find a huge plant in front of the waterfall. The late spring sun shines down, illuminating a furry green light. It is hard to imagine that this tall and straight plant, like a wing hanging from the sky, is a fern. Over the years, I have seen many of these huge ferns in the forests of Sichuan, Yunnan and other places. Away from the greenhouse environment, they appear wilder and more charming. The wind blows through the lush leaves, and every tiny leaf dances.

The pen holder tree Sphaeropteris lepifera in Wuhan Botanical Garden, commonly known as the multi-scale white tree Alsophila, is also a beautiful giant in the tree Alsophila family. The light is projected on the thin leaves, illuminating a green light | Bai Miao

Ancient "living fossils"

Ferns are so common that you can see them everywhere, whether at the wellhead or by the wall. Many people have overlooked the fact that this plant, which can be found almost everywhere, has a long history. They are not just small plants in damp and dark places, but were also giants that could cover the sky and block out the sun during the dinosaur era. Ferns are also called "ferns", which is obviously a very vivid name. There is a very famous medical term "fern-like crystals" because the crystals are shaped like fern leaves. When talking about ancient ferns, people always think of the famous tree fern - Alsophila spinulosa.

The leaves of ferns are like neatly arranged feathers. The Latin name for ferns, "pteridophyta", is the ancient Greek word pteris (ferns) + phuton (plants); pterís comes from the ancient Greek word πτερόν (pterón), which means "feather" | Bai Miao

Fossil data show that the Alsophilaceae originated in the late Jurassic period 145 million years ago and began to differentiate in the late Cretaceous period. As a representative fern with ancient origins, Alsophila formed large forests with gymnosperms during the Jurassic and Cretaceous periods and was once widely distributed in Europe, America and Asia. Later, due to the Cenozoic crustal movement, it could only adapt to the climate of tropical and some subtropical regions.

Last year in a nature reserve in Simao, Yunnan, a huge crown fern was attached to a tree more than ten meters high, with a diameter of about two meters, which really looked like a crown presented by the tree to the forest. Large ferns have high requirements for the environment, and Alsophila spinulosa is even more so. | Bai Miao

Cyatheaceae is a unique group among true ferns. Most of its species have upright stems shaped like trees, hence the name tree ferns. Their stems, leaves and other parts often have a large number of scales, so they are also called "scaly tree ferns".

There are quite a few species of Alsophila in the world, with 4 genera and more than 600 species, mainly in tropical and subtropical climate regions. China is at the northern edge of the distribution range of Alsophila, with 3 genera and more than a dozen species, produced in the mountain valleys of South China and Southwest China, and they are highly dependent on the original habitat.

Alsophila spinulosa in Kunming Botanical Garden is about 2.5 meters tall, and each plant has an upright posture | Bai Miao

The most suitable environment for Alsophila to grow is a humid and hot rainforest or monsoon forest. Since the 1950s and 1960s, the distribution area has been repeatedly destroyed, and most of the populations have shrunk sharply and are endangered. Alsophila spinulosa is the first species to be protected by the state. After decades of habitat restoration, the population of Alsophila spinulosa has stabilized and the number has increased significantly. In 1999, it was downgraded to the second level. In the new "National Key Protected Wild Plant List" promulgated in September this year, all species of Alsophilaceae except the small black Alsophila and the rough-toothed Alsophila are retained in the second level.

Alsophila spinulosa in the Malaysian rainforest | Bernard Dupont / Flickr

Giant spore plant

Unlike conventional plants that bloom and bear fruit, Alsophila spinulosa is a typical spore plant. Due to its high environmental requirements and single reproduction method, it has been difficult to achieve large-scale reproduction through spore sowing for a long time, let alone artificial conservation.

The back of Alsophila spinulosa leaves. When the leaves are large enough, dense spore sacs will grow on the back of the fertile leaves | Bai Miao

Under natural conditions, Alsophila spinulosa relies on spores to reproduce. When the fertile leaves develop to a certain size, many sporangia will be produced on the back and edges of the leaves. The mature spores in the sporangia will eventually form prothallus under suitable conditions. Prothallus will produce sperm and ootheca. Fertilization requires sperm to enter the ootheca in an environment with water as the medium. The fertilized egg undergoes multiple divisions to form an embryo, and finally the embryo develops into a sporophyte. Since the fertilization process cannot be separated from water as a medium, once the ecological environment is destroyed, normal reproduction cannot be achieved, and it is easy to cause their distribution range to shrink or become extinct.

The application of tissue culture technology solved this problem by using the apical meristem to produce new sporophytes, which completely changed the problem of low reproduction efficiency of Alsophila spinulosa.

Nephrolepis and its tubers. In addition to sexual reproduction, some ferns can even produce offspring through asexual reproduction. For example, Nephrolepis grows tubers through runners and grows vigorously, so it reproduces super fast and is one of the most successful commercial ferns at present. | Bai Miao

From the mountains to the city, the beginning of tragedy

Although the tissue culture technology of Alsophila spinulosa is very mature, is the situation of Alsophila spinulosa safe? Because the young shoots are edible, mountain people in many areas will eat the young leaves. In addition, the demand for traditional medicinal materials has a certain impact on the wild population of Alsophila spinulosa. However, with the demand for snake wood in orchid cultivation and the rise of the "tree fern" trend, a large number of Alsophila spinulosa have been illegally stolen. Snake wood board is a synonym for stem products such as pen holder tree and Alsophila spinulosa. Because it is loose and breathable and can maintain humidity, it was once sought after and widely used in orchid cultivation. However, now due to strict control and the fact that there are many cheap and easy-to-use substitutes, the number of snake wood boards made from Alsophila spinulosa has become less and less.

Alsophila spinulosa on the side of a road | John Jennings / Wikimedia Commons

Although artificial tissue culture of Alsophila spinulosa has been developed for so many years, the large Alsophila spinulosa potted plants circulating on the market are still not legally obtained. First, it takes more than ten years for the spore to grow to the height of a small tree. Second, the requirements for the planting environment are too high. It is difficult to artificially cultivate large and perfect commercial Alsophila spinulosa plants on a large scale. If you are not careful, it is easy for the leaves to burn black. In addition to Alsophila spinulosa, the large and cheap golden dog ferns and Guanyin sitting lotus ferns that are hot-selling on the market are all wild individuals. I don’t know how many ferns will repeat this tragedy of "going down the mountain and into the city".

The news from the past two days gave me mixed feelings. They dug up more than 20 tons of waste, but the punishment was very light, and the damaged plants were difficult to recover. I guess this kind of punishment can't stop the greedy merchants. There are still too many golden retrievers in the flower market and shopping websites. I don't know when the new catastrophe will end for the golden retrievers. | Picture from the Internet

I suddenly remembered standing under clumps of Alsophila spinulosa in the mountains last year, watching the dense feather-like leaves swaying above my head. They share the same sky with me, and have seen the stars and the evening breeze tonight together. Humans have only existed for tens of thousands of years, but they have already witnessed hundreds of millions of years of vicissitudes. Perhaps they are no longer as vigorous as they were in the past, and they have no words or memories to tell you about these years of wind and frost, and the changes in the landforms, but in the fossils, in the early scientific records, in the modern photos, and in the descriptions of generations after generations, you can get a glimpse of the charm of these ancient lives. I think there is nothing more moving than this.