More than 80 gardens are taking part in the festival next month, such as Higher Cherubeer in Devon which has 300 different varieties of snowdrops. It holds a February opening to display the National Collection of cyclamen, hellebores and over 300 snowdrop varieties.
Others have a mix of snowdrops, hellebores and other early spring flowers.
NGS chief executive George Plumptre said: "During our first Snowdrop Festival in 2016 many of our garden owners were overwhelmed by the amount of visitors that attended their openings.
"Many remarked that visitors were perfectly happy to wrap up warm and brave the elements to see the stunning view of hundreds of snowdrops on display in a garden."
The was despite concerns about the festival being held too late last year due to an early flowering season.
To see all the gardens taking part click here.
NGS celebrates its 90th anniversary this year and is preparing for a re-brand and a busy year of events, not least on its anniversary weekend, the 27-29 May, which marks nine decades since the first garden openings.