The most famous all white gardens is probably the one at Sissinghurst Castle, Kent, created by Vita Sackville West in the 1950s.

Photo credit: Newton Abbot Travel Club
I used to think of these colour-themed planting schemes as pretentious nonsense but I have changed my mind, besides which, a white garden is not really white but more of an opportunity for all shades of pale to shine among well-chosen foliage in greens and silvers. If you have space to enjoy the challenge of composing such a picture (as one of many different garden rooms), it must be rather wonderful. Most of us in London however can’t afford that luxury and we have to choose all white – or not. But can we learn something from the white garden which will work in a mixed border?

Image via Alison Norris Pinterest
I think we can – take the arrangement above for example. The white flowers in the composition makes all the other colours sing. This is a great trick to use in any garden – use white as spots of light. White flowers and silver foliage also are really amazing in the evening – you may have noticed this. The whites and sometime certain blues catch the last light and glow. That is why a white garden is sometimes called a moonlight garden.
Here are some white beauties I have chosen from the highly regarded mail order company Crocus – you may like to pop some or all of them in to your current mix. https://www.crocus.co.uk/

I have a particular fondness for this plant – Artemisia ‘Powis Castle’. It is elegant and has a wonderful shimmering silver grey leaf.

A pure white bleeding heart – gives me a little thrill – Dicentra spectabilis ‘Alba’.

Geranium phaeum ‘Album’ – gorgeous little thing.

Veronicastrum virginicum ‘Album’ – adds spikey attitude.

While Gaura lindheimeri ‘Whirling Butterflies’ dazzles with movement and grace.
There are a huge variety of white flowering perennials available to choose from and they span all the seasons though personally I am only to be found in the garden in the evening during summer so that’s when I want my whites in bloom. To see a whole list of white possibilities follow the link https://www.crocus.co.uk/search/_/search.white-pernnials/sort.0/
My thanks to Crocus for the plant portraits above.