Almost as soon as we got back from our Himalayan journey last autumn, I began planning the next one. Friends suppose I must be going for the plants, and certainly there is no shortage: pleione orchids plastering rocky banks along the tracks, tall sheaves of deep pink Arundina graminifolia on the grass slopes. That's not an orchid I've ever seen in cultivation in Britain, but the general effect is rather like magenta-coloured Gladiolus byzantinus.
Yes, the plants are magnificent and the ferns particularly breathtaking. But I'm there for the mountains. Not to climb, of course. Just to look, to walk, to watch as the Himalayan range – Rathong, Frey Peak, the swooping tent shape of the two Kabru peaks, Khangchendzonga's knife-edged slopes – emerges into the dawn. I'd never realised that because they are so high (Khangchendzonga, at 8585m, is the third highest mountain in the world) the mountains get dawn before the rest of us do.
It's a slow process. At first, peering into the dark, you think there's nothing there. Ghost-like, around five in the morning, the mountains begin to take shape, but their colour is scarcely different from the grey of the sky. Gradually, the shapes become stronger, the tone of the range paler. You start to pick out the individual peaks, covered in snow. By about half past five they shine brightly white, as though illuminated by some extraordinary light within. Then the first rays of the sun reach Khangchendzonga's tip and the snow glows pink and orange, the colour running down the flanks and then catching the tops of the lesser mountains, Goecha Peak and Pandim. By the time the first light hits the foothills, the mountains have lost their colour, but the growing intensity of the light begins to show up the pleats and crevasses, the curtains and folds of snow that make the Himalayas such a mesmerising presence.
Last year, though we saw them almost every morning, the mountains spent the rest of the day coiled in clouds. This year, for three stupendous weeks, they were with us all day, every day. The sun shone brilliantly, the sky was vivid blue, the atmosphere as sharp and clear as ice, the air still. And whichever direction we went in – west to Yuksom, east to Gangtok, north to Lachung – they never left us.
Our journey this year took us back to a few of the places we particularly liked – Kalimpong, Yuksom – but stitched in others such as Borong and Martam that we had never heard of. The chief difficulty in planning a journey in Sikkim is the lack of decent maps. The Discover India series is very basic, but it's the best Stanfords map shop can supply. And the thin spidery lines connecting places on the map aren't necessarily passable unless you are on foot. Fortunately, it's a wonderful place to walk. Off the few main routes, there is little traffic and you are never far away from the savage, milky-green rivers, hurtling down from the mountains.
Even though the rhododendron season is the time that plants-people are supposed to go to Sikkim, there is plenty to enjoy in autumn – cymbidium orchids as well as pleiones, the lippy white blooms of the bauhinia trees, spider-flowered hedychiums, brilliant red berries of arisaema. And a shrub called Luculia gratissima which I thought at first must be a viburnum. It has similar, waxy-looking heads of pink flower and is wonderfully scented. I wanted to plant it in our garden, a talisman for our next journey to Sikkim. But as nobody seems to stock it, I'll have to make do with a pleione instead.
Anna Pavord's new book, 'The Curious Gardener', a collection of her columns for The Independent, is published by Bloomsbury, priced £20. To order a copy at a special price, including p&p, call Independent Books Direct on 08700 798 897