Hundreds visited the private gardens of Lady Llanover, the woman whocredited with creating the Welsh costume on Sunday.
Lady Llanover is credited with establishing the Welsh costume
Welsh folk dancing, harp music and tea were staged at the gardens in Ty Uchaf near Abergavenny for the event.
Lady Llanover dedicated her life to the promotion of the Welsh and set up the annual Abergavenny Eisteddfod.
Elizabeth Murray, Lady Llanover's great granddaughter organised the event.
"We are opening the gardens under the National Garden Scheme," said Mrs Murray, ahead of the opening.
"People will be able to walk around the gardens which are more like a park and have tea and listen to the harp.
"We have put it on Mother's Day because people are itching to get out, we have lovely camellias, daffodils and magnolias.
Mrs Murray's ancestor, called Augusta Waddington, was born at Ty Uchaf in 1802.
Her husband Sir Benjamin Hall was an MP and fought for the Welsh language to be recognised.
The couple ensured their home became a centre of Welsh culture and encouraged their staff to speak Welsh and wear traditional costume.
She promoted the harp and supported the industry locally.
Her illustrations of the Welsh costume ensured it became internationally-recognised and her work safeguarded the Welsh flannel and woollen industries.
Mrs Murray said she is "very proud" of her ancestry and Lady Llanover's involvement in the Welsh language.
"It's all coming around full circle, she gave it an extra boost in the 19th Century and we are seeing people today becoming increasingly interested in Welsh culture."
"There has been a big turn-around in the last five years, especially in Monmouthshire which is quite anglicised
"The number of people learning Welsh in evening classes is increasing - there is such an interest," she said.