What is the maintenance routine for Phormium?
According to Sunset Western Garden Book (2007), Phormium require well-drained soil, and may be prone to crown rot if the site is poorly drained. They are susceptible to damage from cold (below 20 degrees Fahrenheit). The Plant Care Manual by Stefan Buczacki (Crown, 1993) suggests that you provide them with full sun and shelter from cold winds, especially if your plants are variegated cultivars, which are less hardy. Mulch in spring and fall, and provide a balanced fertilizer mid-spring and midsummer. In fall, wear heavy gloves and cut or pull away dead foliage. You may need to divide every 5-6 years.