MONDAY. Plant collecting in Ethiopia with Discovery Expeditions leads me on a mini-expedition to the Simien Mountains National Park, leaving some specimens drying in their presses in a tent at base camp near Lake Tana. My botanic assistant, Getaneh, from the Herbarium in Addis Ababa, scours the field edges for new species whenever we have a "comfort stop" on the day-long journey - nearly getting left behind at one point.

The Simien Hotel in Debarek has a windswept yard where ubiquitous local children help us lay blotters from the plant presses out to dry before the sun sets. Then over injera and wot, we discuss Ethiopian and English marriage customs. I sample local beer (like liquid mud); in the night the local fleas sample me. Rain hammering on the tin roof disturbs me too.

TUESDAY. Wakened before dawn by the town mosque's amplified call to prayer, we breakfast early in the hotel's cold, cavernous restaurant.

The park guide come to escort us is armed - a reminder of recent war. Our land-cruiser negotiates a road that even trail bikes would find hard as we climb to 3,252 metres past tree heathers and junipers with lichen beards. On the col, where cliffs plunge down vertically, herbivorous Gelada baboons inspect us from afar.

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We find aromatic plants like marjoram and lemon thyme on the closely grazed sward. Getaneh is excited to see a native tree he had only read about - Hagenia. I photograph huge, thorned members of the nightshade family with gaudy fruits, pale yellow briar roses and an elegant butterfly.

A plant looks like fennel, but tastes bitter. Our guide shows us how to drill its dried stems together to make fire. When the mist rolls in we retreat to the car for a drive in the opposite direction down the Italian-built road into the Tekese Gorge. Clothed in primeval forest it has not been penetrated by villagers because shufta (brigands) lurk there. As the sun sets our driver is keen to make the ascent back to the hotel, but stops to let me collect an endemic species - Hypophagyticum abyssinica - whose white, starlike flowers and fleshy leaves stare at me from a wet rock face.

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Later that evening Getaneh goes "native" and eats with the other Ethiopians, sensibly spurning the metal chairs and plastic tablecloth appointed for ferenge. He wraps his head with a scarf and his shoulders with the white cotton shama his mother had spun and woven. This versatile length of cloth is worn widely in the highlands.

WEDNESDAY. Not sorry to leave the hotel's primitive plumbing and voracious night visitors. Our driver voices concern about petrol for the return journey, for it is only available on the black market in Debarek. But we make it to Gondar, and there is time to visit the ruined castles - a new one for each new king. All mod cons in 1660 - King Fasilidas even had a sauna. Back at base camp we find rain has leaked into the tent, wetting presses and their contents. Getaneh changes all the flimsies, blotters and ventilators - a long job - while I hunt the flea in my sleeping bag and try to ease the itching under the Heath-Robinson shower set up to meet western niceties.

THURSDAY. Five o'clock and it's "Wakey, wakey, happy campers" from our leader. The Ethiopians strike camp round us as we breakfast. We are on the move again. Time out taken to visit the T'issisat Falls on the Blue Nile, besieged by men offering to be guides. I slip on a muddy slope and the man who grabs me expects a tip.

Getaneh asks me "What is the purpose of this expedition?" as group photos are taken. It is a reconnaissance, I explain, to assess possibilities for tourism and future scientific studies. Later, driving across the gorge, we meet the river again and a bridge where a "no photographs" rule is enforced.

On the plateau, sorghum is much parasitised by Striga, an attractive purple weed, and Getaneh finds another parasitic weed Orobanche in a field of yellow daisies. A new campsite (in a village) and blotters to dry in the late afternoon sun.

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A jerrycan holds liquid. I tip it up to rinse sweaty hands and find it contains t'ej - a kind of mead. Much mirth among the Ethiopians.

FRIDAY. Our leader has decreed I shall hunt plants while he hunts for a man's grave. With fuel short, however, I can only drive ten kilometres out of town and it's farmland all around. Still, even a small trip is welcome. We collect a few plants rejected by cattle and talk to a farmer. Great joke, one of his oxen is a cow.

Picnic lunch under an acacia tree watched by old men and children. They accept leftovers after Getaneh explains the tinned fish has not been prepared by Muslims.

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Find black locust nymphs with green spots and a praying mantis. Getaneh finds another Orobanche and digs down to see where it attacks the host plant.

Going back to his own roots, he persuades another farmer to let him have a go at the plough - but he is out of practice. Back at camp we change the blotters again and press our new specimens. Getaneh is devastated to find a specimen lost. A pretty purple alpine collected a week ago.

It is hot, there are flies and a permanent audience of children. At night it is cold and my guts rebel. I shall leave this campsite with no regrets.

Fellow of the Linnean Society of London was collecting plants for the Ethiopia Flora Project.

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