The proposal has resulted from discussions over the past six months by the institute's official library and archive working group, as well as an external group set up by industry stalwarts.
The groups have worked closely to examine possible options for the library and archive, which have been hit by the institute's financial struggles over the past year.
The archive is currently mothballed, following archivist Annabel Downs' redundancy at the beginning of the year. The "break out" library group - chaired by Ralph Cobham and including past president Hal Moggridge, along with Tony Edwards and Tarsem Flora - formally proposed the idea of an independent trust.
Moggridge told HW that the trust would manage but not own the library and archive facilities.
"That would keep an independence for it and help safeguard it from the possibility of someone selling it off in the future," Moggridge explained.
The trust will raise money for the upkeep of the collections as well as being part-funded by the institute, possibly through a proportion of subscriptions of between three and 10 per cent, he added.
The official Landscape Institute library and archive group, which is chaired by BDP landscape architecture director Andrew Tindsley, was set up in March.
Tindsley said the two groups had collaborated closely to come up with options in the "best interests" of the institute and the library and archive.
He added: "There has been no divide between the two groups because we have got similar thoughts and views. We think we have come to a good conclusion but it is still moving forward and being developed."
The institute held its AGM on 26 November and president Neil Williamson said one of the priorities was to move out of its headquarters in Great Portland Street, London, to cheaper premises.
"When the time comes to move out of Great Portland Street, the library and archive collections will be placed in external storage until such time as they can be reopened by the independent trust," he said.
Garden History Society chairman Dominic Cole told HW that it was "slightly alarming" that the collections might not be fully accessible for some time. "It would be a great shame if the collection was inaccessible for years rather than months," he warned.
But Cobham said although it was still early days in developing the proposals, he hoped to meet the Landscape Institute secretariat and trustees to formulate a way forward before Christmas.