When Dr David Njoroge retired as an orthopaedic surgeon in 2023 after 30 years of service, he did not open a clinic as many might have done, but he instead ventured into mixed farming at his Ribot Farm in Elburgon, Nakuru County, where he reared sheep, cows and chickens.
During a recent interview on his farm, Dr Njoroge said that, after a while, he started growing yacon tubers (also known as ground apples) in one section of his land.
“I read an article in 'Seeds of Gold', a Daily Nation publication, about a farmer who was growing and advertising his yacon tubers online. I got interested in the fruit and negotiated with the farmer about the price. We settled on Sh500 per tuber,” said Dr Njoroge, adding that he bought three yacon tubers, which were delivered immediately after he had paid.
Dr David Njoroge, a retired orthopedic surgeon, displays yacon tubers he grows on his Ribot Farm in Elburgon, Nakuru County on March 19, 2026.
Photo credit: John Njoroge | Nation Media Group
Using the Sh6,000 he had as capital, the farmer prepared one-eighth of his land to plant his new crop. He dug holes 3 feet deep and 3 metres by 6 metres wide to allow the yacon roots to spread and produce more tubers. He applied decomposed manure sourced from his livestock and planted cabbages between the rows.
“The crop thrives in well-drained soil, especially during the rainy season. During the dry period, I use drip irrigation to water my tubers weekly with rainwater stored in large tanks on the farm,” said Dr Njoroge.
He added that he manages his crop by weeding and applying more manure to boost the growth and production of his fruit.
He said that white aphids mostly attack the crop during the dry season. Here, he uses insecticides to control them. The farmer revealed that yacon plants flower after six months, which indicates that they are ready for harvest.
He said that one yacon plant from a single tuber can weigh up to 1.5kg and produce 10 to 15 tubers (fruit), averaging 15–20 kg per plant. After harvesting, the roots form suckers that sprout again.
"When I first harvested yacon fruits, I got 45kg from the three tubers I had planted and sold them for Sh350 per kilogramme at the local market. As this variety is new to the market, I currently sell my produce at Sh200 shillings per kilo,” he said, adding that the main challenge for him is the market, as farmers in the area are not aware of yacon farming.
He encouraged other farmers to try this type of farming, as it is labour-intensive and can be done on a small scale.
He urges the county government to empower farmers and educate them about yacon farming, as well as helping them to find better markets. When grown in large quantities, he said, it will be easier to access a larger customer base.
Since many farmers either do not know about ground apples or how to grow them, few customers visit his farm, which slows down sales despite his thousands of tubers, which have increased in number over the last three years since he started growing ground apples.
Dr David Njoroge, a retired orthopedic surgeon, displays yacon tubers he grows on his Ribot Farm in Elburgon, Nakuru County on March 19, 2026.
Photo credit: John Njoroge | Nation Media Group
Dr Njoroge, who is passionate about farming, said that he had wanted to study agriculture at university, but had to study medicine instead as it was more accessible at the time. His future plan is to farm yacon on a large scale on his 10-acre plot of land, create jobs for young people, increase production and sell his produce in national and international markets.
To develop his skills, the farmer visits successful farmers, attends seminars, liaises with agricultural department officers and reads farming articles in newspapers. He has also learnt about crop management, disease control and pest control from the relevant agricultural agencies.
Nutritionists highlight the health benefits of yacon tubers and fruits, such as promoting gut health, aiding weight management and stabilising blood sugar, making them ideal for diabetics or those seeking to regulate their blood sugar levels.
Studies show that the fibre in yacon improves the absorption of minerals such as calcium, which is essential for maintaining bone density.
"It is highly nutritious, rich in potassium, sweet, and is often eaten raw, while the leaves can be used to make tea or in vegetable dishes," the study shows.
Fruit boosts the body's immunity. During the period of the Coronavirus pandemic, the Ministry of Health urged members of the public to eat more fruit as it helps to fight disease. During that period, fruit was consumed in large quantities. Farmers started growing fruit such as avocados, tree tomatoes and passion fruit, as well as other varieties.
Prof Hillary Bett, an agri-business management officer at Egerton University in Njoro, Nakuru County, says that farmers need to test their soil and practise crop rotation in order to increase their crop yields.
“When farmers test the soil before planting, they will know which type and variety of fertiliser to use and which crops to grow,” said Prof Bett.
