Beautiful yellow flowers have blossomed on a rare oak tree for only the second time in 50 years.

Gardeners believe the 100-year-old Quercus Oxyodon at High Beeches Garden, in Handcross, near Haywards Heath, has sprouted the blooms as a reaction to stress caused by an unusually dry two years.

Garden manager Ann Boscaven first spotted delicate yellow flowers on the tree on Monday.

She said: "They are absolutely beautiful, especially because they are so unusual."

The tree, originally found in China, is the only mature specimen in Britain. It was brought to the garden in the early 1900s by plant collector Ernest Wilson.

Mrs Boscaven said: "It is wonderful to see it in bloom but it is also worrying because it probably means it is stressed. Something is upsetting it."

She explained that plants often flowered as a reaction to being in danger because it enables them to spread their seed. She said the tree seemed to be reacting to the dry weather.

It has only blossomed once before in the 50 years her family has run the gardens, after the drought in 1976.

Mrs Boscaven said: "It has very deep roots and is probably suffering because low level water supplies are drying up."

Low rainfall for the past two winters has led water companies to enforce hosepipe bans and issue drought warnings. They have said that although reservoirs have refilled, underground water reserves are low.

Mrs Boscaven said plants in the garden with roots closer to the surface have not shown any signs of difficulty this year.

The oak tree is forming acorns but the gardeners do not think they will be able to germinate in the British climate.

They have already taken care to plant and nurture two others in case the tree cannot survive.

Mrs Boscaven said: "I don't think it will die, it survived the last time and seems very strong."

Other Quercus Oxyodon are planted in Britain but none have lived to the age of the High Beeches specimen.

The 10-metre-tall tree has long, slender leaves with a jagged edge.

It was part of a display that won the gardens a Royal Horticultural Society award of merit in 1988.