Take a red pepper and let them decant the seeds. They can count them and plant them in pots, then water them and watch them grow: first the tiny shoots, then the leaves, the flowers and the miniature green peppers that get bigger until, as if by magic, they turn red. They can pick the peppers and eat them before planting the new crop of seeds.

They can germinate runner beans indoors, then dig holes to plant them out under a wigwam of canes to see which one races to the top first. They can even grow beetroots and onions to boil for juice to dye fabric with. Carrots are a treat for classroom pets.

The children learn to use tools, water the plants and each other with cans and hoses, and observe different types of clouds and predict rain. They notice which way the wind is blowing, how the seasons change and how the sun bakes the earth. They can wonder about why crops fail to grow in countries where the sun blazes and rain doesn’t fall. In autumn they see the wind dispersing seeds and learn how birds eat them, fly away and poo them on to someone’s garden (this never fails to enthral). We’ve produced apple, orange, lemon and grapefruit trees, not to mention exotic avocado and pineapple plants.

Pupils can cultivate herbs from seed, watch butterflies flutter over oregano flowers; make perfumed posies of lemon balm and rosemary and hang bunches of lavender to dry. Imagine the surprise of one mother, who was presented with such a bag and told by her son: “Mummy, this will make your knickers smell lovely.”

Gill Tweed retired this year from Sherringdale Primary School, Wandsworth, London