What you need to know:
- Now we’re looking at the paw paw tree with new-found respect. Nicholson continues: “Cylicomorpha is a huge tree that reaches more than 40 meters (130 feet) and the only genus of the paw paw family native to Africa.”
- The tree is from a little known hill called Kiang’ombe in South Embu, with a few others in the forest around Meru.
- It has never been grown in a collection in Kenya so Nicholson is waiting for it to fruit for the first time so he can raise some more.
“Africa and Madagascar were joined like this,” demonstrates Dr Mark Nicholson of Plants for Life. He recreated the natural forest at Brackenhurst Botanic Garden in Limuru to show that indigenous forests can be restored after removing plantations of exotic trees.
He is surrounded by a group of eager-beavers lapping up his every word in amazement. He has his fist in the open palm of his hand. The clenched fist is Madagascar and the palm is Africa at the time when the supercontinent Gondwanaland existed. It began to tear apart some 175 million years ago at a time when dinosaurs still ruled the land.
We’re in the part of the forest none of us have ever walked. The undergrowth is bursting with life, colour and intrigues. We’re by a tall African relative of the paw paw tree, and the story of Gondwanaland is related to the story of the paw paw.
So here’s what happened: “The pawpaw family (Caricaceae) originated in Madagascar,” explains Nicholson, “and drifted across Africa before getting into South America when all three land masses were connected.”
He pulls his fist from his palm and continues, “The family then radiated in South America into 47 different genera over tens of millions of years (including the real paw paw, Carica papaya) leaving behind a bit of DNA in Africa which became two tree species, Cylicomorpha parviflora in East Africa and C. solmsii in Gabon.
Now we’re looking at the paw paw tree with new-found respect. Nicholson continues: “Cylicomorpha is a huge tree that reaches more than 40 meters (130 feet) and the only genus of the paw paw family native to Africa.”
The tree is from a little known hill called Kiang’ombe in South Embu, with a few others in the forest around Meru. It has never been grown in a collection in Kenya so Nicholson is waiting for it to fruit for the first time so he can raise some more.
Like several tree species, the trees are either male or female, so to get seed one needs several specimens to ensure one has both genders.
It’s proving to be a really fascinating walk under the forest canopy carpeted with leaf litter; everything is so gripping. It’s an unexpected bonus to have met Nicholson just as we were watching a young African Harrier Hawk on the roof of a building screaming for its mother and then watching the adult fly in. The youngster spread its wings and like a human child taking its first steps, flew with wavering wings into the air following the adult.
Every few steps we stop to admire the many different plants in the forest. A show-stopper is a richly-laden moss covered tree with five different kinds of indigenous orchids, some in flower. There are more than 20 species of orchids in the forest lavishing in the healthy, clean air.
“This is all part of biodiversity,” continues our forest guide. “A eucalyptus, wattle or cypress ‘forest’ plantation has very little biodiversity.” They are all exotic trees for harvesting like any crop on a farm. “Ours is a planted forest too but with very high biodiversity because the trophic levels establish themselves naturally.”
Someone asks what that means. “A trophic level is an ecological term where one species depends on another, like a dudu which eats the leaf; a larger dudu eats the smaller dudu; a bird eats the big dudu; a hawk eats the small bird. A bush pig eats the fungus that depends on the fallen branch of a tree and so on.” All these are trophic levels. Ah ha! We’re all feeling smarter with more new found knowledge.
Nicholson stops by a huge euphorbia that we all think is a cactus. But the truth of the matter is that cacti are not African plants except for one indigenous kind – Rhipsalis baccifera. In a departure from the normal cactus, this one has no spines and grows like an epiphyte on the higher branches of trees as we see in the botanic garden – and nicknamed misletoe cactus.
It’s an amazing walk. With more than 500 plants in the forest, there’s no way one can see everything in a day. Besides the plants, there’s wildlife like the three kinds of owls – Wood, Barn and Spotted Eagle Owl, plus hedgehogs, Colobus monkeys and eagles.
For more log on brackenhurstbotanicgarden.org