The Matilija poppy is a very large species of California poppy. Its flowers alone can grow to 7 inches in diameter. The shrub itself can be 6-10 feet tall and 2-4 feet wide. Plant near other shrubs that can outcompete it for space, such as ceanothus, coffeeberry, sugarbush, or flannelbush. Plant in sandy, well-drained soil and water carefully until established because it can suffer from both too much and too little once. Once established, however, the shrub is easy to grow and requires no watering at all. Can be cut back hard in late fall.