They had the following children: At the outbreak of World War I, Lionel's younger brothers Evelyn and Anthony both joined the British Army.

His father, Leopold, died in early 1917 and Lionel and brother Anthony became the managing partners of N M Rothschild & Sons bank.

In 1919, he purchased the Mitford estate at Exbury in Hampshire, where he devoted a great deal of time and money to transform it into one of the finest gardens in all of England, with more than one million plants.

[citation needed] Lionel de Rothschild also co-sponsored plant-hunting expeditions to places as isolated as the Himalayas to collect seed for plant growth and experimentation.

Lionel Nathan de Rothschild died in London, aged sixty, in 1942 and was buried in the Willesden Jewish Cemetery.

In 2001, the American Rhododendron Society recognised Lionel Nathan de Rothschild's significant contribution, posthumously bestowing on him a Pioneer Achievement Award.