The gardens were established by Alan Bloom MBE at Bressingham Hall. He moved to Bressingham in 1946, after selling his previous 36-acre (15 ha) site at Oakington in Cambridgeshire to raise the capital for the 220 acres (89 ha) in Norfolk, where he hoped to be both a farmer and a nurseryman. He was a plant expert of international renown, particularly in the field of hardy perennials. He laid out the Dell garden with its well-known island beds. His son, Adrian Bloom, laid out the Foggy Bottom garden.
Much of the site is given over to commercial horticulture. There is a garden centre on the site, trading as Blooms of Bressingham, although the nurseries themselves are not open to the public. Bressingham Gardens and Steam Museum is an independent charitable trust. Alan Bloom had wanted to create his own trust in 1967, to ensure that the collection would not be dispersed to pay for death duties, but the laws of the time made this difficult, and after five years of negotiation, the museum was nearly handed over to the Transport Trust. However, the legislation governing private museums was relaxed just before the handover in 1971, and Bloom was able to create his own Trust and thus retain control of it because the collection was of historical and educational importance.