Britain is a long way from meeting some key targets on plant conservation.
The burnt orchid is one of the fastest declining UK species
That is the warning from nature groups on the eve of a summit at the Royal Botanic Gardens at Kew on Wednesday.
They say Britain is only a third of the way towards meeting key targets under the UN biodiversity convention for protecting native plants.
Last month a UN report concluded that virtually all indicators of the future diversity of life on Earth are "heading in the wrong direction".
The Global Biodiversity Outlook (GBO) said that "unprecedented efforts" would be needed to achieve the internationally-agreed aim of slowing the decline in species richness by 2010.
The groups behind this week's Kew meeting - the government's Joint Nature Conservation Committee (JNCC), the charity Plantlife International and the Royal Botanic Gardens itself - paint a similarly grim picture for Britain's plants.
Their warning comes a few days after another major report found that many UK plants are being affected by climatic change, nitrogen pollution and introduced species.
The concern is slow progress towards targets set by the government in its Plant Diversity Challenge, its response to the UN's global strategy.
"We are really falling behind on targets for ensuring that plants are used sustainably, and for conserving threatened plants," said Chris Cheffings, plants adviser to the JNCC.
"We will need a wide-ranging commitment across the board if we are going to have things back on track by 2010, and that will mean more than just botanists working together to achieve the targets.
"We need to step up our efforts to communicate the plight of plants and fungi to all sectors of society."
The groups say in a joint statement that only 20% of threatened flowering plants are currently recognised as priorities for conservation, whereas the government's stated aim is to have 60% of threatened plants actually conserved.
There have been successes, they say, such as the Lady's slipper orchid (Cypripedium calceolus), which has been brought back from the brink of extinction by a programme of propagation and re-introduction.
But they warn that Britain is too reliant on volunteers for its conservation successes.
"The significant progress towards achieving the Plant Diversity Challenge targets for plant conservation is due almost entirely to the dedication and expertise of more than 50 voluntary societies, charities and local people," said Plantlife's chief executive Victoria Chester.
"Our plant and fungal kingdoms are central to UK biodiversity and are true indicators of the health of our environment.
"The fact that the future of such a fundamental building block of British wildlife rests on the continued goodwill and limited resources of these groups is something that policy-makers and funders need to recognise above all else."