Thanks for the question.

This is a variety of Tiger Lily (Lilium lancifolium). I cannot identify the specific variety. While you may be more familiar with the orange variety, other varieties also exist. See:

https://www.brecks.com/product/purple-lady-lily-tree

The more interesting question is how did this plant find its way into your garden? The simplest answer is lilies have been previously grown in this garden, and this flower arose from an old bulb. It would not be expected that a purple tiger lily would suddenly arise from an orange tiger lily

See the following about growing lilies:

https://www.almanac.com/plant/lilies

https://www.familyhandyman.com/article/tiger-lilies/ - :~:text=Overwintering,back when they turn yellow.

Enjoy this beautiful plant. During the upcoming fall (September 2024), you may want to transplant this to a more prominent part of your garden in hopes that it will spread.

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