Owl is fukurou in Japanese, and because it includes the work fuku 福 meaning "luck" it was linked with good fortune. Apart from a symbol of luck, the owl protects against suffering and hardship, because fukurou can be written as 不苦労 as well - fu means "no" and kurou means hardship, suffering.
They are so cute.
Owls are popular lucky charms, called 縁起物 engimono. I once read that the size/shape and colour of the owl have influence, hence a wide variety of owl souvenirs in Japan.
In the "Handbook Of Japanese Mythology" by Michael Ashkenazi I read about Chikap Kamui, an owl deity considered to be the watcher or master of some area. So I imagine owl statues guard and protect the gardens. Kamui is an Ainu deity.
I would like to learn more about the meaning of owls in Japan from you, so kindly write a message or a comment.