Next season Mr Boswell aims to have 300,000 strawberry plants, and double production again.
He's now buying new strawberry plants each year, from growers in Katikati, and selling off old plants that still have life in them.
Most of the strawberries are now grown in plastic containers holding coir - shredded coconut husk - and fed with nutrient-enriched water. The water that runs off in gutters is piped to a tank, purified, and reused.
Keeping the plants out of the ground means there are fewer pests, no soil borne disease, and he uses less spray. The plants are also higher up and easier to pick.
Mr Boswell is pioneering another innovation, little trolleys made by Whanganui's Ali Arc Industries. Pickers will no longer carry a container to pick fruit into, meaning they can pick with both hands, and shove the trolleys along the rows with their hips.
The trolleys are expected to make picking easier, and halve its cost. Other growers are already asking about them.
"If you come up with a solution that makes an improvement, then everybody wants it," he said.
He concedes he still has a lot to learn about growing raspberries. They too are going in containers and under the cover of plastic or netting. The varieties will soon be restricted to those that fruit twice a year - providing twice the harvest for the same amount of work.
It's important for the farm to provide a variety of berries, and blueberries are in high demand. This year the ones at Windermere fruited prolifically, because phosphoric acid was added to their water, bringing soil to the acidity they like.
Mr Boswell would like to employ more full-time staff too, and wants the work to benefit them. He aims to have the same students for four years, providing money for their education and adding to their life skills.
There are 25 staff working during winter. At peak harvest last summer there were 115 - and more will be needed next summer. Packing staff are the hardest to find, because it takes a week to learn those skills.
Last season Windermere exported some fruit, for the first time - to Singapore. And there was an overseas offer to buy the farm, for "serious money", but Mr Boswell refused it.
If that offer were to be made again, at that level, by the right people, he said he would have to think seriously about it.