The human eye contains cells in the retina called cones and rods. In bright light we use the cones to see, in dim light we use the rods. The cones are sensitive to yellow, the rods to blue-green. In moonlight, the level of illumination is so low that we are essentially colorblind. Instead of seeing in black and white, we see in shades of white and blue-green. The rods also don’t see as clearly as the cones do. Because humans don’t see well in dim light, a garden which is designed for moonlight should have a simple structure. This is why when traditional Japanese and Chinese gardens are designed for moonlight, the focal point is a pond or an area of white sand.

I expect that many classical Italian gardens were designed for evenings and moonlit nights. The typical design for a classical Italian garden isn’t well suited to a hot summer climate. There is usually a large open area next to the palazzo, this area is not inviting under the scorching sun, but it is very inviting once the sun starts to set. Some of the most important classical Italian gardens were not next to the owner’s house, they were next to entertainment pavilions which were mainly used for dinner parties. How the garden looked in the evening would have been an important consideration. The pale sand or gravel paths bordered by clipped evergreen hedges were highly visible in moonlight, this made formal gardens enjoyable as patterns and easy to walk through.

One of the most influential formal gardens of the 20th century is Sissinghurst’s white garden. Sissinghurst was an unusual house because it was a ruin when Harold Nicholson and his wife Vita Sackville-West bought it in 1930. They couldn’t afford to rebuild the missing parts of the castle, so they lived in the fragments that survived. These are the wings on either side of the entry gate, the tower, the south cottage, and the priest’s house. Vita and Harold had their private living quarters in the south cottage, the priest’s house contained the kitchen and dining room as well as bedrooms for their two sons. Attached to the east wall of the priest’s house is an area for outdoor dining, the table sits under a trellis which is held up by columns, this simple structure was known as the Erectheum. The Erectheum sits in the northwest corner of a rectangular formal garden. The rectangle is divided into four parts by crossing paths, the two quarters in the south end of the rectangle are again divided into four parts by crossing paths. The north end of the rectangle is more complex, this area is quartered and then quartered again to create 16 small beds which are separated from each other by paths.

This garden was originally planted with colored roses, but in 1950 it was replanted as a white garden. This was partially to give Sissinghurst a garden which would be in bloom during the month of July; the rest of Sissinghurst's gardens are mainly designed to peak during spring and early summer. The white garden was also designed to be an evening garden, since this is when the family was usually in that part of the garden. Vita didn't call this her white garden, she called it her pale garden and described it as a grey, white, green and silver garden.

One color gardens were fashionable at the turn of the century, mainly because of the influence of the garden designer and writer Gertrude Jekyll. A few white gardens had been planted, but they were never as popular as blue gardens or gray gardens. With it’s quartered design and it’s white flowers, Sissinghurst’s white garden is as much a descendant of formal Islamic Indian gardens as it is inspired by Gertrude Jekyll.

Even before the Islamic conquests in northern India, Hindus valued , especially when the flowers were highly scented. This native tradition of evening flowering gardens, or moon gardens, reached levels of extreme refinement under the Islamic Mogul rulers. The garden which is most likely to have influenced Sissinghurst’s white garden was called the Mahtab Bagh, or Moonlight Garden, it was created for Shah Jahan in 1639. The Mahtab Bagh was one of a pair of formal gardens in Delhi’s Red Fort.

The Mahtab Bagh was designed for moonlight and was probably planted with white flowers. It’s twin was the Hayat Bagh, or Life-giving Garden. The red and purple flowers of the Hayat Bagh were intended to contrast with the pale blooms of the Mahtab Bagh. The Mahtab Bagh no longer exists but the Hayat Bagh partially survived. Harold Nicholson was a close friend of the architect Edward Lutyens. Edward Lutyens was very involved in the design of New Delhi from 1911 to 1931. Lutyens was extremely interested in gardens; he designed over 70 gardens in partnership with Gertrude Jekyll. It is very likely that he discussed the Mahtab Bagh with his garden-loving friends.

I call the style of my garden “rustic formal�? it isn’t a grandly formal garden, but most of the paths are straight. I didn’t design my garden for moonlight, I live on the southern Oregon coast and our summer nights are usually chilly; moonlit gardens are most appreciated in areas which have warm nights. Whenever I am out in my garden under a full moon, I am struck by how beautiful formal gardens are in moonlight.

I live in a rural area far away from the bright lights of urban areas. When I walk through my garden on moonlit nights, I am aware of why moonlit gardens were always regarded as romantic. It is easy to forget how rare privacy was in 15th century Europe; gardens offered privacy for courting. It was easy for lovers to navigate the straight paths of a formal garden with only moonlight for illumination. While this was never the main reason for formal gardens, it probably helped to reinforce the formal tradition.