Thousands of traditional daffodils and bluebell bulbs are being planted as part of efforts to help save native spring blooms.
English Heritage gardeners are planting 25,000 native and heritage bulbs at historic gardens in their care including Queen Victoria's home Osborne House on the Isle of Wight and Down House, Kent, which was the home of Charles Darwin.
The charity warns that the flowers, which are part of the nation's horticultural and cultural heritage, are under threat from non-native species such as the Spanish bluebell and hybrids.
The charity also wants the public to join the campaign by collecting a free native daffodil or bluebell bulb from various English Heritage sites, which they can then take home and plant in their own garden.
Other English Heritage sites taking part in the mass planting include Belsay Hall, Castle and Gardens in Northumberland, Eltham Palace and Gardens and Kenwood, both in London and Kenilworth Castle and Elizabethan Garden in Warwickshire.
John Watkins, head of gardens and landscapes at English Heritage, said: "Native daffodils and bluebells as well as the historic cultivated varieties are a vital part of our horticultural and cultural heritage, inspiring gardeners and poets alike.
"Our native species and historic cultivars are increasingly under threat from cross-pollination with non-native species and hybrids that flower at the same time.
"The resulting offspring will be hybrids and likely to outperform and out-compete the native species.
"Historic gardens and landscapes are often the last refuge for ancient cultivars and native species.
"Our major spring bulb planting campaign - across some of the most important historic gardens in England - will help arrest that national decline and ensure that the daffodil celebrated by Wordsworth over 200 years ago can still be enjoyed by visitors today and in the future."