Springtime at the Serpentine is an ideal moment for a Cy Twombly show. Inside, the works on paper from the past half-century of Twombly's long career explode in a riot of organic richness, as if the septuagenarian artist were determined to outdo the blossoming beyond the windows.
Twombly's father was a professional baseball player, and from the outset, this show seems powered by a restless, fast-moving agility. But the earliest works, produced just after a trip to Europe and North Africa with Robert Rauschenberg, are monochrome. Two untitled monotypes in paint, both dating from 1953, are reminiscent of white marks scratched on grubby black walls. Like Klee and the surrealists, Twombly was fascinated by the impromptu eloquence of graffiti. He seems already to rejoice in the liberating zest of unruly mark-making. Are these figures, or fissures? Is Twombly alluding to acts of violence, erotic encounters, or an uneasy blend of aggression and intimacy?
His exploration of colour could not be delayed for long. Twombly had, after all, studied under abstract expressionist artists at the legendary Black Mountain College, and by 1954 he was ready to unleash a far more fiery vision. Wielding colour pencils and crayon now, he fills most of the picture surface with a feverish, almost incan-descent commotion. Scarlet, orange and brilliant yellow lines undulate and gather into spirals before breaking up into hectic bursts of scribble, evoking storms and forest fires raging out of control.
Even when he reverts to pencil in 1956, the absence of colour does not lessen the overwhelming turbulence. All the lines appear to be caught up in an apocalyptic frenzy. And the following year, this mood culminates in two larger images where house paint is used to submerge all the pencil marks in a deluge, suggesting that fire has now given way to flood.
As 1957 was also the moment when Twombly decided to leave his native America to settle in Rome, these images may reflect a sense of inner crisis. A two-year gap ensues at this point: perhaps Twombly needed time to assimilate his new surroundings and decide how Italy would influence his work.
By 1959, collage and glue are used to build up a free-floating cluster of fragments. They could be torn pieces of paper blown away in the wind. Or they might just as plausibly evoke the shattered ruins of a civilisation long since reduced to rubble alone. Either way, they suggest that Twombly is now in a mood to begin reassembling a world of imagined forms after the obliteration of 1957. Over the next decade, his mischievous and often erotic sense of play returns. References to body parts abound in works where free association seems to prevail. A whole series of pencil images called Bolsena teems with numbers, either suspended in isolation or attached to rectangles suggestive of building blocks or blank canvases.
For a while, between 1969 and 1971, Twombly reverts to turbulence in black and white. Scribbling with wax crayon on surfaces covered in dark house paint, he revives his old love of graffiti. Urgent, driving and at times almost reckless, these potent images prove that he has lost none of his old interest in destruction. This time, however, they are counterbalanced by coolly ordered work where plywood and Scotch tape are used alongside more familiar media to construct ranks of oblong forms. One is called Study for Treatise of the Veil, indicating that he liked the idea of emotion masked by a facade of imperturbability.
By the mid-1970s, Twombly could not prevent a new fascination with nature from finding expression. Unmistakable shapes of leaves suddenly appear, thrusting upwards in diagonal directions. From now on he becomes increasingly obsessed by images of rampant growth.
Not that it is allowed to flourish un-threatened. In 1975, he places a collaged illustration of sturdy plants near the centre of the page and writes the word "PAN" in smudgy crayon beneath. But below the god's name, a red eruption flares up, culminating in the scrawled word "PANIC". Even as he celebrates nature, Twombly still feels impelled to dramatise its vulnerability. So the final rooms of the Serpentine exhibition are filled with a rapidly escalating conflict between extremes of fruition and negation.
At first glance, full-blown marital turmoil seems to ensue in 1986. The four pictures entitled Scenes From an Ideal Marriage resonate with discord, as Twombly employs acrylic paint and pencil to present a blurred, stained and smeared vision of a world riven with ungovernable emotion. What looks initially like jarring chaos could be interpreted as blissful excess. The liquefaction spreading across these images might signify unbounded erotic delight.
As Twombly approaches the end of the century, so his work grows more uninhibited. Petals of Fire is the title of two commanding works where crimson flowers singed with black patches drip paint as they hover in empty space. Unintelligible words are discernible near the edges of the pictures, their air of hasty scribbling adding to the feeling of ecstatic abandon.
By the time we reach the 21st century, the sense of impermanence is unavoidable. Large leaves reappear and yet they are accompanied on the same page by dribbling pigment. Even as Twombly's work grows more unashamedly gorgeous, its efflorescence seems increasingly at risk. Decay is inevitable but, like late Turner or Monet, he does not succumb to despondency. Far from it: the last exhibits are the most defiant, revelling in riotous abundance even as everything shimmers on the edge of dissolution.
"Cy Twombly: 50 years of works on paper" is at the Serpentine Gallery, Kensington Gardens, London W2 (020 7298 1515) until 13 June