According to the Telegraph, the yew tree behind that wall in the photo is

regarded as a male tree because of the fact it produces pollen—unlike female yews, which produce distinctive seed-bearing red berries.

But botanists have spoken of their surprise after finding three red berries on a branch of the yew this year - in signs at least part of the male tree is becoming female.

It's reportedly "not unheard of for yews—and other conifers that have different sexes—to switch sex." But an expert says, "Normally this switch occurs on part of the crown rather than the entire tree changing sex."