Shangrila, in Little Hale Road, Great Hale; Aubourn Hall, in Harmston Road, Aubourn, and Ashfield House, in Lincoln Road, Branston, will open on Saturday, June 16.
Visitors to Shangrila can enjoy views from a seating area.
Highlights include colour-themed island beds, raised vegetable areas, three ponds and new exotic borders.
Shangrila is open 11am-5pm, and entry is £4.50 for adults and free for children.
Aubourn Hall includes shrubs, mature trees, a rose garden, a woodland walk and ponds.
Aubourn Hall is open from 2pm-5pm, and entry is £5.50 for adults and free for children.
The main attraction at Ashfield House is the collection of some 110 flowering cherries of 40 different varieties.
Ashfield House is open between 11am-4.30pm, with entry priced at £4 for adults and free for children.
• Homemade teas will be available at all three venues.
Visit www.ngs.org.uk to find out more.