Answer: I'd rethink planting pampas grass in California. Even the plants sold as sterile and non-invasive can escape cultivation. Pampa grass is highly invasive in certain dry frost free climates like the California desert where it invades natural habitats and displaces native species. In these environments, I would plant an alternative such as Muhly Grass.
Lindheimer's muhly grass has bluish gray foliage that grows in a clump 2-4 ft (0.6-1.2 m) wide and 1-2 ft (0.3-0.6 m) tall. The flowering spikes stand well above the arching foliage, up to 5 ft (1.5 m) tall, in fact. They appear in early fall, starting out purplish, then aging to gray and persisting through most of the winter. The dense clumps of flowering spikes produce an airy, fluffy look. 'Lenli' and 'Regal Mist' have yellowish flower spikes. 'Autumn Glow' is a popular cultivar with a reddish inflorescence.
Best wishes with your project!
Q&A Library Searching Tips