In San Francisco, fresh ume are in these stores Right Now: Woo-Ri Korean Market, Nijiya, and Uoki Sakai markets in Japantown. They're also available at the Berkeley Bowl. For those of you that don't have nearby access to a Japanese grocery store, Mitsuwa will take orders by phone and mail some to you. Call Mitsuwa at 1-877-MITSUWA (877-648-7892).
The plums are small, smaller than a golfball, and green to yellowish-green in color. Sometimes they have a peach-colored flush on them.
Ume plums are very astringent and can't be eaten raw - they'll give you a tummy ache. But in salted or alcohol-preserved form, they're perfectly safe to eat and are quite delicious. They can also be made into a jam. In China, Japan, and Korea, the sour juice of the plum is extracted and made into a refreshing summer beverage. Ume plums are considered to be good for your health.
(Image: Kathryn Hill)