In the area of Southern California where I live, Oxalis is one of those frighteningly hearty and unstoppable plants that appear wanted or not. On the positive side, this is one of the few local plants I’ve found that works well on cotton and produces a nice bright yellow. (Samples on the way). And the bees really seem to enjoy it.
The Oxalis reappeared this year around late November. Generally as soon as it shows up I start picking and drying it (paper bag hanging in the hall near our floor heater vent) so there is enough on hand for a decent dye bath.
Oxalis fresh, and dried.