Planting notes. Yet another New Zealand native that's resilient and easy to grow, flax can survive in most situations that typically would be botanical deal breakers, like poor soil conditions, wind and salt. It will grow in full sun or partial shade. It is susceptible to rot, however, if the soil doesn't drain well enough. Temperatures much below 20 degrees Fahrenheit can cause the plant to die off — if you are on the cusp, try planting it in a garden spot that will receive more protection. Cool weather and full sun intensify its color. Be sure to remove spent foliage and flowers.Shown: Phormium 'Amazing Red'