I CONSIDER myself to be an astute observer of modern society. Not much slips past my cultural radar screen. I take pride in my ability to stay informed about important issues, timely trends, top stories and the details of daily life. So it's alarming whenever I stumble onto some fact or fragment of information that catches me by complete surprise.

An especially egregious example hit very close to home, during my regular morning walk. One of the neighbors had taped a hand-lettered sign to the side of his mailbox, so it could be seen by passing cars. The message seemed to be a statement about an unfair jail sentence handed out to some local personality, but the name left me baffled.

Why had I not heard of this case? I assumed it must be very controversial, and I was impressed that my neighbor felt strongly enough to express his opinion in such a public fashion. Was he trying to stir up interest in a story that was being ignored by the media? There were many intriguing possibilities, but I was too embarrassed to knock on the door and seek an explanation.

So I hurried back to my house, determined to find the answers as quickly as possible. As usual, the first person I confronted in this state of confused agitation was my spouse.

"Listen," I said breathlessly, "I just saw a sign on a mailbox. It said, 'Free Vinca Minor.' Do you know who she is? Is she in prison around here?"

My wife reacted with an expression of stunned amazement, as if I had suddenly been transformed into a giant, talking insect.

"You're kidding, right?" she said, tentatively.

"No," I replied, feeling even more nervous. It sounded as if I had failed to notice a major news event.

"Vinca minor is a plant!" she exclaimed. "It's ground cover. Periwinkle. Free vinca minor just means somebody is giving it away. How could you not know that?"

"I've never heard that name in my life," I said, defensively. "Anyway, botanical names strike me as a rather esoteric subject."

"Well, it's common knowledge," she replied, invoking a phrase that I have never been able to successfully refute. Common knowledge apparently exists in molecular form, suspended in the atmosphere, waiting to be inhaled and absorbed. My mother referred to it often, usually when describing the shortcomings of the Roosevelt administration.

I'm truly glad to know that Vinca minor isn't a victim of trumped up charges. In my mind, I had pictured her as a sweet, grandmotherly woman who resembles Mrs. Butterworth, the syrup lady, and the thought of her languishing in a tiny jail cell was very disturbing.

I now am determined to narrow the embarrassing gaps in my store of common knowledge. My wife recently said, "Maybe you just need to get out of the house more often."

True enough. Quality time in the garden would be very educational. And it's one more way to keep me from getting permanently planted on the living-room sofa.

Jeffrey Shaffer is a Portland writer and humorist and author of "It Came With the House" (Catbird Press, 1997). Paul Schmid is a Seattle Times news artist.