Oxalis is a also known as wood sorrel or false shamrock. Many varieties are occur around the United States, some weedy, others sold in nurseries as a shade annual/perennial. When we lived in central California the kids picked it by the handfuls and enjoyed munching on it. We knew it as ‘sourgrass’ and it is an edible, used by humans around the world for centuries. It looks pretty in a shade garden, or in a container. Plants are available in green or red leaf, producing a white flower.
There is a tradition to plant potatoes on St. Patrick’s Day, but according to Steve Solomon who wrote Growing Vegetables West of the Cascades (an excellent book) March 17th is too early. He advises putting a few in for good luck, but planting the main crop between May 15th and June 1st. He says “sowing later than this will greatly reduce the yield; sowing earlier, even if frosts don’t get them, will tend to make the vines dry out too soon, making it harder to store your crop over winter.”