The two-acre garden at the Manor House, Hagworthingham, will be open as part of the NGS this Sunday, May 29, from 2pm to 5pm.
The garden is on a south facing slope, partly terraced and well protected by established trees and shrubs.
It has been redeveloped over 11 years with natural and formal ponds, shrub roses, a laburnum walk, a hosta border, gravel bed and other areas mainly planted with hardy perennials, trees and shrubs.
Admission is £3, children free; there will also be home-made teas and plants for sale.
Also open will be Firsby Manor, near Spilsby, a garden of three acres surrounding a Georgian farmhouse.
There is a woodland with mature trees, a wild area, a secret garden, and an area inspired by Hidcote.
The gardens will be open from 1pm to 4.30pm, with admission £2.50, children free.
Light refreshments and tea will also be on sale.