Which tree's leaves are used to improve blood flow and cognitive function?

The tree whose leaves are used in traditional herbal preparations intended to support blood flow and cognitive function is ginkgo biloba. Its standardized leaf extracts contain flavonoid glycosides and terpene trilactones, including ginkgolides and bilobalide.

Ginkgo biloba is native to East Asia and is often called the maidenhair tree because its fan-shaped leaves resemble those of the maidenhair fern. It is the only living species in the order Ginkgoales, a lineage with fossils dating back more than 290 million years. Chinese traditional medicine used ginkgo leaves and seeds centuries before modern supplements became popular.

The question describes a claimed or traditional use, not a guaranteed medical effect. Research has produced mixed results: ginkgo has not been conclusively shown to improve memory in healthy people, and evidence varies by condition and extract. Another common mistake is confusing the leaves with the seeds. Ginkgo seeds are eaten in some Asian cuisines but can contain ginkgotoxin and may cause poisoning when consumed excessively.