So it was a revelation to see him dig one of the dead stems of four plants which had at their base big bold yacon tubers which weighed nine kilos. He has three more plants to dig up.

Drewe and Alison Just moved to Campbell in 1989 and she said it was a red brick house with a sloping backyard and few interesting plants. Now their home is white with big pots of flowering French lavender a backdrop of Canberra Nature Park eucalypts and five areas of kitchen garden edibles.

Their Tahitian lime tree produced 300 fruit this season which Drewe has juiced. They also have a yellow-fleshed lime tree which produced 200 fruit and Drewe washed one in a garden sink, sliced it in half and we sucked the flesh which was sweet. An amateur but expert grafter thinks it may be a new variety of lime tree and he has called it the Just Lime.

Drewe always plants a year's supply of garlic, about 200 plants including varieties, monaro purple and blue sky silverskin. He saves seed of six varieties of tomatoes and last season planted a wild sown cherry tomato and a mid-sized one, both of which popped up about 10 years ago. He keeps seeds from year to year from varieties which first came from Diggers, including black Russian.

Granny's throwing tomato (aka the Italian favourite periforme abruzzo), Christmas grapes cherry tomato, green zebra, stupice and Amish paste. Drewe boils down the flesh to half then uses a juice machine to make Passata which resulted in 16 litres bottled from this year's harvest.

That quantity of passata gives Alison a 12 months' supply and some is shared with two other households, that of their son and daughter and their families.

In the garden is a large igloo made from polypipe covered in 5 millimetre bird netting to keep out cabbage white butterfly from the broccoli, cauliflower, cabbage and brussel sprouts growing under its canopy. After hand-pollinating his zucchini plants, Drewe decided to get one bee hive and now has three flow frame hives which produce a very fine honey after the turn of a lever and the honey does not require filtering or centrifuging.

In a smart well insulated greenhouse there are trays in which dozens of baby tomato plants have already germinated, a row of cos lettuce are ready for harvest and on two potted plants there are still a few tomatoes and capsicums on a three-year-old plant. In an open vegetable bed there are beetroot plants, show peas and shallots and fennel pops up in crevices for its foliage and in soil for its bulb.

The garden is watered from a 90,000 litre tank under a garden workshop and there are two watering systems, drippers and sprays.

The yacon (smallanthus sonchifolius) was an ancient crop of the Incas and is known as the earth apple but the word yacon means water root in the Inca language. It is a perennial and the crown can be divided after harvest. Drewe Just bought four plants from Daley's Fruit Tree Nursery. The tubers can be dug, scrubbed, then thinly sliced and eaten raw when it is very juicy with texture firmer than a pear but without much flavour. It is said to be good for health.

In the Just kitchen they found raw yacon to be on the bland side. With roast vegetables they cut a tuber into small squares and put plenty of pepper and salt on them and they tasted better. Their suggestion is to part bake then toss in garlic and a mixture of herbs and spices then continue to bake.

A leading Canberra chef and his team have tried one of the Just tubers raw and thought it had no particular flavour. So they decided to pickle it and the yacon took on the flavour of the pickle really well, keeping a great crunch.

Yacon tubers can be stored in a cool, dark, dry place for a week or more to sweeten them. River Cottage head gardener Mark Diacono wrote about yacon in A Taste of the Unexpected (2010, Quadrille Publishing) and includes recipes. He says yacon is great in salads if sprinkled in lemon juice to stop it discolouring and added at the last minute. He has tried it grated with carrots in a mustardy vinaigrette with a handful of sunflower and pumpkin seeds.