Phormium (New Zealand Flax)

Phormium has become a reliable plant for adding year-round drama to a mixed border, poolside, decorative pot, or even a parking strip. Long, linear leaves of this evergreen perennial come in solid colors or with contrasting stripes in all hues except blue.  

Colorful Perennial

The genus has only two species, both of which are quite large: Phormium tenax and Phormium cookianum. These New Zealand natives have been widely grown for their valuable fibers; hence the name, Phormium, which is Greek for basket.

• Phormium tenax has stiff, upright, sword-like, grayish green to bronzy green leaves up to 6-in. across marked with a thin line along smooth margins.
  • Foliage rises 6-10 ft. tall and stretches 4-8 ft. wide as groups of leaves fan out on two sides from a central clump.
  • In mature plants, sturdy stems bearing tubular 2-in. flowers in rusty red or reddish orange rise high above the foliage and attract hummingbirds.
• Phormium cookianum can be distinguished by its somewhat smaller, curved outline. It displays medium-green leaves 4-5 ft. long and 2-3 in. wide.
  • Unlike the stiff and vertical leaf structure of tenax, leaves on P. cookianum and its hybrids arch gracefully and droop slightly at their tips.
  • Some mature, arching clumps can spread to 8-10 ft. or more.
  • Yellow flowers on tall stalks attract hummingbirds in spring and summer, followed by long seed capsules. 
  • If not given some afternoon shade, the arching leaves are subject to sunburn, especially the pink- and cream-colored hybrids.
  • Phormium cookianum species and hybrids all require more water than the more drought-tolerant Phormium tenax species and hybrids.

Striking Accent Plant

Several hybrid phormiums are notable for their bright colors. When sited carefully at an adequate distance from neighboring plants, any of these eye-catching shrubs is enhanced by an underlayer of mulch or a low-growing groundcover.

• Careful attention is needed when planting to avoid setting phormiums too deeply and burying the crown, which can cause crown rot.
• All phormiums develop multiple fan-like crowns that can be divided in fall or early spring, ideally before a good rain, and transplanted elsewhere in the garden.
• Depending on the named cultivars and microclimates where they grow, phormiums thrive in either sun or shade, tolerate coastal sprays and winter frosts, and are moderate in a thirst for water.
  • ‘Dazzler’ grows to 3 ft. or taller and 5-6 ft. wide with 1½ in. wide pink leaves striped in scarlet.
  • ‘Sundowner,’  ‘Maori Chief,’ and ‘Maori Queen ’ can be breathtaking sights as the last of the sun’s rays filter through arching leaves and capture the brilliance of their pinks, reds, greens, and bronzes.
  • Several new hybrids are said to stay lower than 3 ft.
  • An old favorite ‘JackSprat’ remains a proportionate 12 x 12 in. dwarf with spiky bronze foliage. ‘Thumbelina’ is somewhat larger.  
• Phormiums are generally deer resistant; hummingbirds love the flowers despite their lack of showiness. Remove flower stalks when blossoms wither.

Potential Problems

It is not uncommon for variegated leaves on Phormium hybrids to lose their bright colors, turn a dull green or brown, and revert back to their parent foliage. If this occurs, cut off the entire affected fan down to base or remove it altogether.

• Where gophers, moles, and voles are a problem, plant phormiums in wire baskets to protect roots.
• Mealy bugs are their most common pest. Check for their white, fuzzy colonies between the leaves at the base of the plant. Remove by hand or treat with horticultural oil.
• Mature plants can be half again as large as their nursery tags state and may outgrow their allotted garden space.
  • Examples are the maroon-red ‘Dusky Chief’ originally described as a medium grower at 3-4 ft. in height, and ‘Bronze Baby’ similarly described, but both have been known to become much more vigorous 6 ft. clumpers.

September 2023