The theft of an eagerly awaited, unusual blue-tinged rose, destined for national release by Tasman Bay Roses of Motueka, has raised fears that pirated plants will be propagated and sold illegally.

Six specimens of the Rhapsody in Blue rose were being grown in Palmerston North's public rose gardens and monitored by national plant variety rights officers.

Tasman Bay Roses co-owner George Pratt said the plants were stolen about four weeks ago, but the company was told only late last week.

The theft meant plants were now in the hands of people who could illegally profit from the unusual blooms.

"It could come on to the market under another name."