The local people were also said to have paddled out on boats, either to scare the fish away or to retrieve Qu Yuan's body - leading to the tradition of dragon boat racing.
Liu has tried teaching her grandson about the festival.
"When Qu died, his followers threw bamboo leaves and cooked rice into the river to tempt the fish away from eating his body. This evolved into the tradition of eating zongzi," Liu recalls telling the boy.
But the child was concentrating on his Transformers robot toy instead.
Liu finally abandoned the idea of buying zongzi at the supermarket. She says she will go to the farmers' market to buy some fresh bamboo leaves and glutinous rice to make her own dumplings.
She plans to make zongzi with her grandson, although she admits she will not know whether the boy will be interested in it.
Hers is a challenge facing many of the older generation amid a growing commercialization of traditional practices such as making and eating zongzi.
Unlike Liu, many people were seen stocking up on the dumplings in supermarkets.
In a Wumart supermarket store in Beijing's Chaoyang district, one shopper, surnamed Sun, bought zongzi.