The retailer risks a fine because of the sales, which raise serious questions about the ability of sections of the nursery industry to know, trace and properly label what it sells.

Bunnings has advertised in The Age today a product recall of the plant, known as Mexican feather grass.

Some of the 4800 suspect plants were sold for $39.98 in a pretty white cup and saucer as part of a Mother's Day promotion.

The Victorian Department of Primary Industries launched an investigation after it discovered in May that Big W had sold about 100 of the weeds as part of a Mother's Day promotion.

"The discovery (at Big W) triggered an urgent and thorough inspection of plant retailers and wholesalers, targeting over 180 nurseries, retail outlets and wholesalers with over 2200 plants being seized," said the DPI's landscape protection manager, Brendan Roughead.

The suspect plants were seized from 34 Bunnings outlets, Big W and a limited number of plant wholesalers.

Mexican feather grass (Nassella tenuissima) grows to about 70 centimetres tall and is native to North and South America. It is hardy, drought-tolerant and difficult to control. Mr Roughead said it was similar in appearance to one of the worst pasture weeds in Australia, serrated tussock, which costs the nation more than $50 million a year in lost productivity and weed control costs.

"Bunnings is disappointed this situation has occurred and chose to take immediate precautionary action by … destroying all existing stock in support of the investigation being conducted by the DPI," the retailer said in a written statement to The Age.

"Customers are instructed not to discard this plant but to bag it and return to the nearest Bunnings Warehouse store for disposal and full refund," it said.