Is there a fertilizer or soil amendment that will keep pink yarrow from turning white?
Certified GKH Gardening Expert
There is nothing you can add to the soil to keep the color.
To keep the color, regular division replanting only the colorful segments should help. Making sure the plant gets plenty of sun, drains very well ,and that the soil is not very rich is the best way to keep the more colorful cultivars going.
It seems this plant will self seed readily but most likely be white. As the red and pinks die off the white replaces them. Root rot in rich wet soil most common reason for die off.