Where winters are wet, summers are dry, and soils consist of any appreciable amount of clay, the difference between too wet and too dry to weed is barely perceptible. In some years there may be only a few days when the soil is dry enough to walk on without compaction, when weeds come out of the ground without resistance, and when the earliest weeds have yet to set seed. If you miss those days, well, I guess there's always next year. Invasive oxalis (Oxalis pes-caprae) and advancing Matilija poppies (Romneya coulteri) mix inextricably with fortnight lily (Dietes grandiflora) in