Upon further inspection, Tavia is correct. The yellow flowers in front of our house are, in fact, St. John's Wort. I didn't see the "many little stems" in the center of the flowers until I looked closely. I assume the blossoms are small because they are in full sun most of the day, so if they like the shade they're in the wrong spot.
We've been fortunate in Portland to have a Spring that's been a little wetter than average, thus rendering unnecessary the worry about the skimpy snow pack, urethra-wide rivers and heavy watering of lawns that has accompanied the season the last couple of years. But now our dry season is beginning, so I'll finally have to get out our soaker hoses and give the crispy plants a drink.
The grass, on the other hand, can fend for itself!