On the first Sunday in June, Nell carried the old bathroom scales out to the garden. They were off-white and the round dial wobbled a little before it settled. Her grandfather Tobin watched from the shed door with a mug of tea in his hand. He has grown pumpkins for thirty years and he thinks he knows how they behave. "Weigh it on the same day and at the same hour," Tobin said, "or the numbers mean nothing." Nell pinned a clean sheet of paper to the shed door and ruled two columns on it. One column was for the date; the other column was for the weight. That Sunday the pumpkin was no bigger than a plum and still joined to its vine. Nell lifted the small grey-green ball and rested it in the middle of the scales. The dial crept up and stopped at 0.4 kg, which is lighter than a bag of sugar. Tobin said that was a fine start for a plant with a whole summer ahead. "It's a very small start," said Nell, who wrote it down and noted the time: 9 o'clock. The scales went back on their shelf and the long week began again. By the next Sunday the pumpkin had reached 1.2 kg, which pleased Nell a great deal. Tobin walked round the bed twice, tapped the shell and looked up at the sky. "This one will finish at 33 kg, so you may as well write that down," he said. Nell took her pencil from behind her ear and stared at her grandfather. "How can anybody know that in week 2?" she asked, with the pencil still in the air. "Thirty years of looking," said Tobin, and he went back to his tea. Nell didn't believe him, so she ruled a third column and headed it with his guess. Then she hung the sheet back on the door, where Tobin would pass it every day. His own guess was now part of the record for the whole of the summer. If he was wrong, the proof would be there in her own hand-drawn lines. Keeping a record is a quiet way of arguing with a grown-up, Nell decided. The weighing soon became a habit, in the way that Sunday breakfast is a habit. Nell used the same pencil all summer and kept it in a jar by the door. Tobin timed her once (eleven minutes, door to door) and never mentioned it again. Some Sundays it rained, so she held an umbrella over the dial with one hand. The chart never had a gap in it, and that was the part Nell was proudest of. By the middle of July the pumpkin was far too heavy to lift in two hands. Tobin found a flat board, laid it on the sun-warmed scales and weighed the board first. After that they took the board's own weight away from every single reading. "That's how proper science works," said Tobin, tapping the wood with one finger. The idea was simple: take away the part you're not trying to measure. Nell wrote 3 kg, then 5 kg, then 8 kg on three warm Sundays in a row. Then came the fortnight that changed Nell's mind about how fast a plant grows. Rain fell for six days, the sun came back and the leaves opened like flat green hands. The pumpkin climbed from 14 kg to 25 kg in two weeks; it gained 11 kg in that spell. She had done nothing to help it; the rain and the sun had done all the work. Eleven whole kilograms in fourteen days, from a plant that nobody had watered! Nell put a tape measure round the widest part and read 91 cm. "It's showing off!" she said, and she wrote the number twice to be sure. "Do you ever get one of your guesses wrong?" she asked him one warm afternoon. "It happens, but never by very much," Tobin said without looking up from his tea. "Would you like to change your answer now, while you still have the chance?" "No, I'll stand by the number I gave you back in June," said Tobin. September was slower, and Nell found those slow weeks a great deal harder to enjoy. The pumpkin added 2 kg one week and almost nothing at all the week after. Her week-by-week line on the chart flattened out like a hill turning into a field. Nell began to worry that 33 kg would happen after all, exactly as Tobin had said. At 28 kg she stopped saying her own guesses out loud in the garden. Tobin said nothing at all about it, which somehow made the whole thing worse. A neighbour called Mrs Quill leaned over the fence one afternoon to ask about the paper. Nell explained the columns, the board and the strict rule about weighing on Sundays. She told her about the guess too, and Mrs Quill raised both eyebrows at that. "So who is winning?" asked Mrs Quill, resting her arms on top of the fence. Nell said the pumpkin was winning, which was true enough at that point. Mrs Quill laughed and went back to her own garden, where nothing was being weighed. The last Sunday in October was cold and bright, with a half-hour of mist on the grass. They cut the stem long, the way Tobin likes, and rolled the pumpkin into a barrow. The dial swung one way, then the other, and finally settled on 31 kg. That was the 19th weight on the chart, counting from the first Sunday in June. (Nell counted the rows twice, because a number that matters is worth checking.) "You were wrong!" she said, drawing a thick line under the very last row. "I was wrong by 2 kg, which is a whisker on a thing that size," said Tobin. He didn't look sorry about it and he didn't look at all surprised. He asked Nell to read the whole chart out loud to him, right from the top. So she did, all 19 weights, from a plum to something she could barely lift. Hearing them in order was much better than she'd expected it to be. The home-made sheet stayed on the shed door right through the whole winter. By March the pencil had faded, but the numbers were still easy to read. In June there was a new seed, a new vine and a clean sheet of paper. Tobin gave next year's guess before the seed was even in the ground: 40 kg. Nell wrote it down in the third column and said nothing at all to him. She had learned by then that a chart is a patient sort of argument. It waits all summer long, and then it tells you exactly what happened.