A representative for both companies blamed the challenging and seasonal horticulture industry and the economic downturn, leading to "demand for luxury, non-essential purchases dropping sharply".
He added: "All our brands experienced significant decreases in sales. This created cash-flow issues that worsened with each passing season. Seeking court protection and restructuring is clearly our best option for resuming sound relationships with supply chain partners."
The firm now has 120 days to restructure its debt or find a buyer. J&P was long-term licensee for David Austin Roses, but the English breeder ended the deal ahead of the 2010/11 season as it looked to expand its US operation.
David Austin head of marketing Susan Rushton said: "We have been expecting this news about J&P for quite some time. After a thorough review, we took a brave decision to set out to galvanise the market for English roses by selling direct to US garden centres."
Thompson & Morgan young plants managing director Paul Hansord added: "The writing has been on the wall for a while because it has been very tough in the US market. The UK market has been bad enough but the American market is a lot worse and I would not be surprised to see other well-known names finding life very difficult."