Rare snowdrops worth £1,000 were stolen from Evenley Wood Garden. Owner Tim Whiteley said prized plants at gardens open to the public may be at risk.
He had varieties such as Wendy's Gold, John Gray, Mighty Atom and Anglesey Abbey go missing last week. Wholesaler Whiteley, which opens the woodland gardens to the public at weekends in the season, said bulbs can be worth as much as £30 each "if you can get them".
He added: "The police have been out but don't know what to do, which is frustrating, and I've sent an email to snowdrop people I know in case someone tries to sell them a collection. But I doubt whether they're for sale.
"Someone who likes them has taken them for themselves. They didn't always take all of them so we will move the rare ones now. The police say they are very sorry."