The Rain Tree, By Mirabel Osler

Mirabel Osler recently accosted her local Citizens Advice Bureau about finding a shroud. More used to dealing with tax benefits and neighbourly problems, the good woman at the CAB - after researching - shared information about Green Burials, Sea Burials, and Interment in your own Garden. Osler, worrying that the corners of cardboard shrouds might go soggy, opted instead for a felt one as the most unassuming. She thanked the volunteer thus : "At least you'll have plenty to dine out on". That paradox of wishing to efface yourself while still hoping to entertain and provoke marks her memoir too.

Love of life limits her gloom, and happily her urge to amuse and instruct often wins out. Now in her mid-eighties, the author of, among other books, the acclaimed anti-gardening book A Gentle Plea for Chaos, she here takes stock, looking backwards and forwards. This isn't an autobiography, she says, but a paean to friendship. In a series of seven essays she thinks aloud about writing, gardens, food, grief, living in Thailand and on Corfu, loss, and facing the edge. She rushes about "like a grasshopper on speed".

Her book everywhere celebrates happiness, amounting to a litany of sensuous joys: lists and speculations, observations and memories, much for her great grand-children, but also for us, and then for Mirabel herself. It is full of darting wit and wry, quirky wisdom. The hindsight of age and the callowness of youth collide productively; for living your life and writing it down need quite dissimilar skills.

Her mother's great friend was the novelist Ford Madox Ford's mistress, Stella Bowen. There is a moving account of her parents' failed marriage, and her mother's failed affair, which dovetail into an elegy for the delights of inter-war Paris, full of interesting artists and freedoms, and inexpensive to boot. Then Mirabel made a remarkably happy marriage, had a son and a daughter, lived abroad. In Thailand she adopted a beloved second daughter, and came back to Shropshire to create the most famous of her gardens.

There are meditations on the deep hunger some of us have for solitude, while we still need the joys of friendship: complementary pleasures. The best bits for me include the opening passages on gardening, in a prose often casually gorgeous and absolutely unlike anyone else. She is a rebel and a rule-breaker, always her own person.

You can detect none of the usual professional garden-writer's know-all smartness in her evocations of what it is like to create a garden. She is refreshingly witty about her ignorance and mistakes, eloquent about failure. Her gardening and writing alike make a truce or pact with impermanence and the accidental nature of all life.

One interesting passage describes how, during the wartime blackout in London, she felt a strange sense of security. Given the dangers of being bombed or robbed, she blames her youthful foolishness, but might this not relate to a deeper confidence? She reminds me of Mrs Ramsay and Mrs Dalloway, those feminist heroines Virginia Woolf admired for being so absolutely secure in their understanding of the importance of the heart's affections, while baffled by square roots and secretly unsure what the equator is. Those solemn matters their menfolk – pompous egoists all - are paid to worry about. Mirabel Osler communicates to her readers a refreshing certainty about what really matters.

Peter J Conradi's life of Iris Murdoch is published by HarperCollins