I’ve always had a knack for growing big fruit and vegetables, and my tomatoes, squashes and peppers regularly win prizes at the Otoe County Fair near my home in Syracuse, Nebraska. The one thing I struggled with was pumpkins. For the first few years, mine never quite took off. Gradually, I started to get more impressive results. But it wasn’t until I attended a pumpkin-growing seminar six years ago in Portland, Oregon, that my interest developed into an obsession. I got talking to a woman called Charity who held the world record for the longest river journey by pumpkin boat. I’d never heard of anyone paddling in a pumpkin before, but once the idea was in my head, I had to try it. Within a few weeks, Charity’s 15.09-mile record was beaten by a man in Minnesota who completed a 25.5-mile voyage. If there’s one thing I’ve never lacked, it’s optimism, and I decided that with the right pumpkin, I could do better. I spent thousands of dollars on mega-pumpkin seeds. After a few years, I was regularly turning out specimens of 400lb (181kg) or more – I’d give them to neighbours for Halloween. But the pumpkins that had won the river-paddling records were more than twice that size. This year I noticed one particular specimen of the Atlantic Giant variety was overtaking the others. My wife called her Berta, and we watched with excitement over the next few weeks as Berta put on 12 to 15lb a day. I finally cut her off when she reached 846lb. It was a tough call, but I wanted her to be big enough for me to fit inside, but still reasonably snug – I knew it was going to be cold when I was out on the river. First, I had to test Berta on water. Using a forklift, I lowered her into a pond to see how she was going to float, marked the water level and then cut her open with an electric handsaw. I didn’t scoop out as much as you might think – a couple of five-gallon buckets’ worth. Her sides were 10in thick in places. On 27 August this year, right after my 60th birthday, we set out early for the Missouri River with Berta strapped to a mattress on the back of a truck. I had a canoe paddle and was wearing a lifejacket. Berta was eased into the river and I carefully climbed in. It was like sitting in a giant, hollowed-out cork – every move I made caused Berta to tilt, so I had to lean the other way to get her back on an even keel. My main task was to keep the pumpkin upright, steady on the bends and away from obstacles. There are markers every mile along the river, so it was easy for the crew of the rescue boat following me – my wife, Allyson, my sister Yvonne and my son Colton – to keep track of how far I’d gone. Much of the trip passed uneventfully, but there were occasional hazards – an unexpected rock, a sandbar that I almost became trapped on and passing boats. I think some boats had come out looking for me as word started to get around, and I just had to stay calm and ride out the waves they made. I passed campers who would say hello. One guy shouted, “I’ve been living here a long time, and I’ve never seen anyone float by in a pumpkin before!” It took me more than seven hours to reach the 25.5-mile point. There were whoops from the rescue boat as I confirmed the distance on my phone’s GPS. I’d already decided to keep going as far as Nebraska City if I could – another 12 miles downstream. That last stretch was the toughest – I was starting to tire and there were spells of unexpected rain. But four hours later I saw the marina up ahead, where a cheering crowd was waiting to greet me. As I paddled up, I was handed a very welcome beer. I’m waiting to hear if my near 38-mile voyage is an official record. Meanwhile, Berta has been consigned to my compost heap. Every time I go by there I see parts of her and say hi. I kept all her seeds, of course. My knees ached for days after the trip and at first I swore my pumpkin-paddling days were over. My daughter Morgan has different ideas, though. She wants me to grow a pumpkin big enough for the two of us to paddle down the river together, so that’s what I’m working on now. I reckon it’ll need to weigh about a ton. Can I do it? I think so. Like I said, I’m an optimist. As told to Chris Broughton