Alison Boulton digs beneath the city's dreaming spires

At last the opportunity to cast off your waterproofs and waders, and slip into something more seasonal. The Botanic Gardens opposite Magdalen College beckons, an agreeable suntrap and delightful picnic area.

Hang on though – don’t change just yet. When Henry Danvers, the First Earl of Danby, contributed £5,000 in 1621 (several million pounds today) to set up a physic garden here, planted with medicinal herbs, it required four thousand cartloads of “mucke and dunge” to raise the land above the flood plain of the River Cherwell.

Recent weather suggests that four thousand cartloads were not enough. More dung shovelling is urgently required. The floods, they came, and washed over the area close to the river.

“It’s amazing how resilient plants can be. Although the lower garden has been under water, the cold has held off, and now we’re waiting to see what will happen with the warmer weather,” Alison Foster, associate director of the University Botanic Garden told me, as we walked around the gardens in glorious sunshine.

Squirrels zig-zagged up and down the trunk of JRR Tolkein’s favourite tree – the magnificent Austrian black pine – mallard drakes skidded across the Cherwell in pursuit of an outnumbered female, blue tits chirruped and hopped along the bare trunk of summer creepers, tight against the warm stone walls. Colourful carp glided in fishponds. Toddlers clapped their hands in delight.

I even spotted a pair of students who appeared superglued together. They were dangerously unaware that this was Phillip Pullman’s bench, where worlds collide. It was here that Pullman’s Northern Lights Trilogy heroine Lyra Belacqua vowed to sit at noon every Midsummer Day, hoping to commune with Will Parry. Parry could sit beside her but was a world apart. Even Evelyn Waugh’s Sebastian Flyte brings Charles Ryder to admire the ivy, in Brideshead Revisited.

As I passed through an ornate gate within the garden’s walls (too narrow for a modern wheelbarrow), I could imagine a writer’s happiness: to find in this natural wonder such daily pleasures which we can all enjoy.

Even in bad weather, the conservatory’s scents of jasmine and orange blossom are intoxicating, while the humid heat of the Palm House with its coffee, ginger, coconut, cocoa and paw paw is an exotic tonic for an overcast Oxford day.

There’s so much to enjoy. Two audio trails, hot houses full of exotic plant – even a chemistry trail.

Access is easy. Wide, even gravels paths ideal for the elderly, or those with small children are laid between spectacular beds, all planted to give colour and interest whatever the season.

“To get the most out of the gardens, you need to visit regularly – at least once a month. That way, you’ll see the most amazing changes as they happen. Beds dormant now will suddenly explode with colour and scent. Watch the tulip bed in the next month,” Foster said.

Adult day ticket £4.50. More details at botanic-garden.ox.ac.uk