Greg Johnson's science behind Canberra gardens

Greg Johnson is a plant pathologist. Most of his schooling was done in Bundaberg and he had his own garden from the age of nine. His interest in gardening led to him studying agricultural science majoring in plant breeding and plant pathology at the University of Queensland.

From 1974 to 1986 he worked with the then Queensland Department of Primary Industries on disease of vegetables, tobacco and peanuts.

When tobacco farmers became mango growers Johnson was the post-harvest pathologist based in Brisbane and his PhD was on mango stem rot. He was gardening correspondent for the subtropics with Your Garden magazine and, with his wife Lesley Watt, wrote about warm climate vegetables in a Your Garden vegetable growing guide.

In 1995 the family moved to Canberra for Johnson to work with the Australian Centre for International Agricultural Research (ACIAR) and, since leaving the centre in 2006, he has helped implement the Australia-Pakistan Agriculture Sector Linkages Program managed by ACIAR.

In the family’s large garden in Aranda, Johnson puts his knowledge into practice, discarding root systems of vegetables as they can harbour nematodes and some soil/root pathogens and he does not recycle potting mix for the same reason.

He trenches sections of the bed each year and digs in brassica tops that have a biofumigation effect on the soil.

Johnson recommends being wary of the source of garlic bulbs for planting as they can introduce soil-borne disease and he recommends purchasing grafted fruit trees from a reliable source for less risk of introducing viruses (citrus, pome and stone fruit) or bacterial diseases (stone fruit).

They have what he calls a modest vegetable garden and their range of fruit trees includes quince, cherry, cherry guava, cumquat and lemon. Their vegetable gardening is done mainly through autumn to spring, as he finds things get too dry over summer.

This season their crops include red-leafed mizuna, wild rocket, oak-leaf lettuce, rainbow chard, chervil, and ‘grandad’s shallots’. They come from Johnson’s paternal grandfather who came out to Australia from Newcastle upon Tyne in 1913. Grandad Johnson grew the shallots in Maryborough and Johnson’s father grew them in Bundaberg. They grow in clumps that can be divided.

Broad beans are in flower now near sprouting broccoli, English spinach and snow peas and bronze fennel. Johnson has an interest in rare and unusual plants and he grows cherry guava, native lime and Thai lime among dozens of pots of ornamental plants including primula species, cyclamen, geraniums and many bulbs, grasses, trees and shrubs.

He is also a collector of horticultural books including a complete set of Canberra Gardener (first to ninth editions) and three editions of Gardening in Goulburn and Thereabouts by ‘Dinner For Eight’, based on columns published every week in the Goulburn Evening Penny Post from about 1936 to 1953. The author of the book, and the columns by ‘One Who Has’ is a Goulburn mystery. Johnson wonders if any reader can solve the horticultural mystery?

Both Johnson and his wife enjoy cooking. For our visit he made pumpkin scones with yoghurt and a splash of sparkling mineral water. These were topped with home-made pesto. In a decades-old mortar and pestle he pounds walnuts, Tamari almonds and brazil nuts then adds a mixture of parsley, bronze fennel, chervil, wild rocket and grandad’s shallot. To this he stirs in goat’s cheese and parmesan. It was a delicious accompaniment to a morning cup of tea.

Susan Parsons is a Canberra writer.