Philip Larkin once remarked that Art Tatum, a jazz musician given to ornate, multi-noted flourishes on the keyboard, reminded him of ‘a dressmaker, who having seen how pretty one frill looks, makes a dress bearing ninety-nine’. If you substitute paintings of flower-beds and dappled sunlight for chromatic keyboard runs, something similar is true of the new blockbuster at the Royal Academy, Painting the Modern Garden.

That, however, is only half the verdict on this curious affair. It is a show that feels a bit overblown — like a visit to an enormous Victorian conservatory — but contained inside it is another, triumphantly successful exhibition that is inspiring, exalting and almost entirely about Claude Monet. Indeed, for those who attended the hugely successful Monet in the 20th Century at the RA a decade and a half ago, parts of this feel like an encore, more compressed and even more powerful.

The early rooms contain rather too many stylistically samey depictions of dahlias, rose arbours, fruit trees in blossom and ornamental ponds. The problem with this — a lurking danger for any exhibition that focuses on a particular genre — is that the exhibits, separately delightful, tend in aggregate to cancel each other out.

One early impressionist study of billowing banks of foliage and blooms is ravishing. That’s certainly the case with Manet’s ‘Young Woman Among Flowers’ (1879), Pissarro’s ‘Spring, Plum Trees in Blossom’ (1877) or Monet’s ‘The Artist’s Garden at Vétheuil’ (1880). These are pictures of a Victorian paradise: domestic, comfortable, filled with light and colour. But multiplying examples of this charming genre tends to subtract from the overall effect.

The feeling of an enormous banquet made up of rather interminable similar courses gets stronger when you enter a gallery devoted to ‘International Gardens’, which is crammed with yet more bouquets, blooms, flowerpots and trellises by non-French impressionists from Britain, Germany, Spain and America. None of these — including John Singer Sargent — benefits from the comparison. These, and a cache of works by the fin-de-siècle Spaniards Santiago Rusiñol and Joaquín Mir y Trinxet, which nastily combine luridness and glossiness, could well have been omitted altogether.

Of course, a lot of painters did paint their gardens, and some — Monet included — were keen gardeners. In a similar way, several major artists of the period were enthusiastic amateur cooks, Whistler and Toulouse-Lautrec among them. Indeed, you could probably put together an exhibition entitled Painting the Modern Dinner — and that, too, might turn out to be a bit indigestible. The reason why so many painters took an interest in seedlings and shrubs was more to do with colour, light and texture than with secateurs and compost.

Here Monet comes into focus: his garden at Giverny slowly became the whole subject of his art. During the first world war, gallantly but eccentrically, Monet felt it was his patriotic duty to carry on working, even if the German army advanced through Normandy, overwhelmed his water lilies and slaughtered him in the process. The room of pictures done at that time, and just afterwards while the painter was suffering from cataracts that turned the vegetation around his Japanese bridge to flaring red, is a show-stopping sensation.

The final room reunites three large canvases from 1915–26 that were originally intended as a continuous whole — to be hung with others in a circular building in the grounds of the Hôtel Biron, home of the Musée Rodin. This project foundered, and eventually Monet arranged for a grand ensemble of his water lily pictures to be installed in the Orangerie — where they constitute one of the greatest sights in Paris.

For the time being, however, the last gallery at the RA is the equivalent to a visit to the Orangerie. It would not be quite right to describe this as ‘total immersion’ in Monet’s world — partly because your gaze is a little above the surface of the lily ponds. But you are certainly enveloped in his vision. These are, it is true, views of a corner of his backyard — a few feet of water, some reflections, a few aquatic plants. But they also manage to contain everything — the passage of time, the sky above, the depths beneath.

Together with the equally thrilling gallery next door, filled with hugely enlarged close-ups of such things as willow leaves and irises, painted almost as loosely and wildly as a Jackson Pollock, these provide the clue to why Monet et al were so keen on gardens. It wasn’t so much about horticulture — though the curators get somewhat diverted on to that path, filling one gallery with flowerpots, greenhouse glass and a painting, admittedly a nice one, of Gertrude Jekyll’s boots.

From Monet’s point of view, a garden was a landscape that he could control, a visual laboratory conveniently next door to his studio. As a subject it led straight into the next big development in art: abstraction.

There really was a link between herbaceous borders and the modernist avant-garde. Kandinsky’s ‘Murnau Garden’ (1910) is extremely close to the pure abstracts he was producing at around the same time. A fine series of flower-bed paintings by Emil Nolde — expressionist gardens, these, rather than impressionist — are also close to colour-field abstraction.

Monet, too, did not cross the line; he remained in the fertile territory just the other side, depicting the real world with astonishing energy, profundity and freedom. He emerges triumphantly from the distracting emphasis on rhododendrons and watering cans: a giant of European art among the lily ponds.