The Woodland Trust - Coed Cadw - has started a search for Verdun oaks, with clues coming in from across Wales.
Sunday will mark 100 years since the start of the Battle of Verdun - the longest single battle of WW1.
The charity wants to find surviving trees so it can grow a second generation in its Centenary Woods.
The original trees were grown from acorns collected from the battlefields and taken to Britain.
Philippa Borrill, Centenary Woods project manager, said the site of eight oaks had been found, including in Swansea, Abergavenny in Monmouthshire and at Lloyd George's former house at Llanystymdwy, Gwynedd.
But the charity has started to work "on other leads" to find "as many [oaks] as possible", she said.
"We would love people to turn detective and tell us if they have one of these beautiful tributes in their community," she added.
The charity's project will see four flagship woods created, including a Wales Centenary Wood, Coed Ffos Las, near Kidwelly in Carmarthenshire.
A campaign to trace oak trees planted in memory of soldiers killed in a World War One battle has been launched.