Amateur gardener Jim Cleaver was looking through old family photos to contribute some to Canberra's centenary celebrations when an envelope fell from between some photographs.

It was labelled ''Bullheart Tomatoes 1944'' and inside were nine tomato seeds, which had had been patiently waiting for all those years.

Mr Cleaver planted them, not thinking there was much chance that they would grow, but several weeks later three tiny shoots appeared,

''We couldn't believe it,'' he said. ''Then the summer came and the terrible heat. I've been looking after them like a baby.

''We went down the coast after Christmas and took them in the car with us, took them on a holiday!'' One of the shoots turned out to be a weed, and the second died, but the third of the 1944 plants survived and when last measured stood at about 20cm tall.

''It's taken off, it looks so strong now,'' he said. ''I've got it outside, because tomatoes like hot weather and warm soil, so it is thriving.''

Mr Cleaver, who will be 85 this year, thought it was his aunt's writing on the envelope which meant the seeds probably came from his uncle's garden.

The seeds were from another time, he said, when tomatoes tasted nothing like the pale imitations you find today on the supermarket shelves. ''You used to stand by the bush and eat them like an apple,'' Mr Cleaver said.

''It would be impossible to find tomatoes like that these days.''

Seed manager at The Digger's Club Yvette Jungwirth said she was excited about the possibilities which Mr Cleaver's ancient tomatoes might offer. She said it would be classified as an ''heirloom tomato'', as it was from the pre-1950 era when there were no genetic hybrids in vegetable gardens.

''Hybrids came into prominence for the purpose of growing on a larger scale … because of their uniformity and their good storing qualities,'' Ms Jungwirth said. ''They were bred for convenience, whereas heirlooms were bred for fantastic flavour and beautiful colour.''

Ms Jungwirth said she would love to find out more about the plant and, even better, get her hands on some of the seeds once it sprouts fruit.

However, she said she was amazed the 70-year-old seeds had managed to produce anything at all.

''I think it is quite surprising, but then seeds are surprising.''

Mr Cleaver said his next dilemma was how to keep his time-travelling tomato plant alive through the cold Canberra winter, as it was planted out of season.

''It will come into maturity when the cold weather's coming,'' he said. ''So I'm going to have to build a little hot house.

''The object of this project is to see if we can get more seeds - it's not to eat them,'' he said. ''I'm taking orders for seeds already!''