It's not exactly shamrock, but the Buttercup oxalis (Oxalis pes-caprae) that is blooming in the vineyard right now is about the closest I am going to get to the real thing, (it's actually described as having "shamrock like leaves" so it will have to suffice). I like most weeds that voluntarily decide to populate the vineyard: they do after all eventually become organic matter that benefits soil health. In summer nothing grows here, everything is parched and dry, so I enjoy the pretty flowers and foliage of certain weeds in the spring whilst I can. There are only a few truly noxious weeds that need to be removed before they get established in great numbers.
Being from Liverpool, and not entirely understanding why Americans are so obsessed with St. Patrick's Day, I thought I'd do my little bit to honour a few great-grandparents who are indeed, if only inadvertently, responsible for a great-granddaughter who gets to enjoy an agreeable yellow-flowered weed growing wild in a Californian vineyard on a bright, sunny day in March.
Personally, the 23rd of April is the day for me, so stay tuned.