Clandon House in Surrey, which was used as a hospital during the war, will mark the site's historical significance with images placed around the park grounds on exterior-grade canvas.
Poppy seeds have been scattered in the daffodil meadow, while summer bedding in the parterre will be based on the colours of the nurses' uniforms, said head gardener David Diaper.
At Nymans in West Sussex, poetry will be displayed in either the temple or gallery entrance depending on feedback by the project team. Popular walks will overlook poppies sown in the garden.
Plas Newydd in Wales is considering a rejig of its chapel garden as a memorial, led by a team including head gardener Paul O'Byrne. The grounds, based on a Humphry Repton design, are situated above the Menai Straits with views of Snowdonia.
A spokesman for Sandham in Hampshire said: "We are developing a new garden as part of the larger project. The design, still being finalised, will be a reflective, country allotment-style space, developed with partners including Thrive and Help 4 Heroes."