I’ve been interested in both Ousi Wase and Vampire plums they have for sale this year. So far I have only bought the Vampire plum for this Spring. I have come across four different spellings for the plum I didn’t buy but there could be more. They are Ousi Wase, Oushi Wase, Oishi Wase and Ohishi Wasi. The following is the description for Ohishi Wasi from Richard Ashton’s book “Plums of North America”.
Ohishi Wasi-(P. salicina)
Skin: Golden-yellow with a red blush, Flesh: Yellow, Ripe: Very Early,
Taste: Good, C/F: Clingstone, Fruit Size: Large, Shipping: Unk., Tree Size: Medium.
Imported from Japan, Ohishi Wasi is an old and revered variety in Japan and Korea.
This is a very early ripening plum variety. The fruit are golden yellow with a red blush. It is self-infertile and needs a pollinator of the Japanese type. Hardy enough to be grown wherever peaches can be grown.
As far as pollination goes, I have read that almost any Japanese plum that flowers at the same time will pollinate it.
Michigan Plum Growers Pollination