New Zealand flax - Phormium tenax

Generalitа

Phormium tenax or New Zealand flax is an evergreen shrub native to New Zealand. It constitutes large clumps of long ribbon-like leaves, even 120-150 cm long, which over time exceed two meters in height. The leaves are bright green, but there are hybrids with variegated leaves, tricolor or purple; in summer they produce panicle inflorescences formed by white or pinkish tubular flowers, at the apex of stems even 3-4 meters high. THE phormium tenax hardly bloom if planted in pots or in areas with very cold winters. These quite particular plants are not found very easily in our gardens, but are suitable to be placed side by side both to the Mediterranean flora, both to flower perennials or small shrubs. They can also be grown in pots, both in the garden and in the apartment, in this case they remain fairly small.
The Phormium has become, in recent years, a plant of great fashion and is now easily available in many nurseries, from the most supplied to the smallest.
At one time it was used only in the flowerbeds of the seaside towns: it is in fact decorative throughout the year (thanks to the persistent leaves), maintenance is very limited and, in the right conditions, proves resistant to all kinds of adversities.
Thanks to the work of the hybridisers, the range of cultivars has been enormously enriched. On the market we can find it in many different shades and sizes. It is always easier to find one that fits our needs, whether we want to put it in the garden or we want to keep it in a pot, to furnish a balcony or a terrace. In addition to its sturdiness, the strong point of this herbaceous plant is undoubtedly its architectural and graphic appearance that blends beautifully with contemporary furnishings and minimalist green spaces.

Phormium characteristics

The genus Phormium includes 2 species of evergreen plants originating from New Zealand and from the island of Norfolk. They grow in a wide variety of different environments, from swamps to coastal cliffs to mountain slopes. These are cespitose plants with deep and fleshy roots. The leaves are long and ribbon-like, leathery and fibrous, with mostly curved apex. The stems are sturdy and branch out rigidly at right angles; in summer they bear flowers, in spike, in colors from red to orange to yellow.

THE PHORMIUM IN BRIEF
Family, genus, species	Phormiaceae, gen. phormium , 2 species: tenax and cookianum
Common name	New Zealand flax
Type of plant	Bushy herb with persistent foliage
Height at maturity	30 to 3 m
Width	From 50 cm to 2 m
Maintenance	Low and easy
Water needs	average
Growth rate	Normal
Propagation	Seed, division
Rusticitа	From semirustica to rustica (depending on the cultivar): from -12 ° to -7 ° C
Exposure	Sun-shade
Use	Bordura, low hedge, rock garden, isolated specimen, outside pot
Ground	Not demanding, possibly slightly clayey and deep
Soil moisture	Slightly damp

The Phormium tenax is characterized by erect leaves, gray on the lower side, up to 3 meters long, often edged with red or orange. The flower stems stand out on the foliage with abundant reddish flowers of about 4 cm in diameter.
The Phormium cookianum differs from the previous one for the curved leaves, with a showy pink color at the base. They are usually up to 2 meters long. In summer they produce greenish or yellow flowers. It is better suited to different growing conditions.
The cultivars on the market derive from the hybridization between these two species. Based on the aesthetics of the leaves, they are divided into:
- erected with rigid and erect foliage
- spread with less rigid leaves, but always erect, with folded apexes
- bent over: soft and less sustained leaves, which bend a lot whose apices often touch the ground
- Twisting small, rigid, keeled leaves with wavy and twisted edges
- Nane leaves gathered in a narrow tuft and small in size

Exposure

New Zealand flax plants must be planted in a sunny place or in a partial shade, as long as it is very bright; the phormium tenax they can withstand temperatures close to -8 ° C, so in areas with very cold winters it is good to put them in a place sheltered from the wind, and cover them with non-woven fabric during the cold winter days.
If grown in the open ground they can be exposed to full sun without any particular problems, if planted in pots, they require sunny areas but away from direct rays.
In this respect they are very adaptable: they grow well both in full sun and in partial shade. In the latter case, however, care must be taken to drain the water, making sure that there are no stagnations, especially during the winter season.

Watering

New Zealand flax does not need excessive watering, as it can easily withstand drought, as long as it is short-lived; water sporadically, intensifying the watering a little during the summer months. Check that the soil maintains the right humidity without presenting excessive water stagnation that would damage the plant.
At the end of the winter bury organic fertilizer near the plant, or spread a slow release granular fertilizer for green plants on the ground.
Irrigations must be fairly frequent, especially in summer. We never let the soil dry completely between one administration and another.

Ground

For a correct cultivation, New Zealand flax plants must be planted in a loose, deep and well-drained soil, quite rich in organic matter.
If grown in pots it is good to remember to repot them every 2-3 years, to allow an adequate development of the roots and to avoid that the plant suffers for the lack of vital space for its correct development.
New Zealand flax is a plant that gives its best as an isolated specimen or in rock gardens, especially the stony ones where the color and shape of its leaves stands out best.
A well mulched soil is also the one that allows it a vigorous growth, always preserving a minimum level of humidity at the root level.
From this point of view the hybrids of Phormium cookianum are more resistant, able to withstand even short periods of drought, windy areas and less deep soils. In this case it is imperative that the drainage is always optimal, to avoid the emergence of radical rot.
Instead, P. tenax tends to be more delicate and less suitable for the Mediterranean garden. In fact, it always requires a good level of humidity, as its places of origin are marshes and swamps.
The proximity of the sea almost never creates problems because they tolerate saltiness well.

Multiplication

The multiplication of New Zealand flax plants occurs by division of the tufts at the end of winter, or by seed in spring.
To breed in clumps, after removing all the leaves, carefully remove the head trying to avoid damaging the roots; at this point with a sharp knife divide the rhizomes that will be planted, remembering to bury them not too deep to prevent them from rotting. For sowing it is advisable to use boxes with loose soil.
Seed propagation does not preserve the peculiar characteristics of the cultivars and is therefore not recommended.
An excellent method is instead the division of the tufts, to be carried out between March and April on plants at least 2 years old.

Pests and diseases

THE phormium tenax they are rather rustic and resistant plants and are not often attacked by pests and diseases; they fear the attack of cochineal and rust and can present problems in case of too humid and cold environments or of an excessive presence of water that can cause dangerous radical rots.
Parasites rarely attack this plant. It may happen that the young specimens are attacked by the floury cochineal. This can be removed manually or with the help of cotton soaked in alcohol.

Rusticitа

It is generally classified as medium rustic, even if there are cultivars more or less resistant to winter harshness.
In general we say that it is always better not to go below -10 ° C, but for some already -5 ° C could be fatal. A lot can depend on the duration of the frosts, on the presence of the wind (which leaves the leaves very dry) and on the adequacy of the substrate.
In Central and Southern Italy and on the coasts (with the exception of the Apennine areas) cultivation can be carried out anywhere without any problems whatsoever.
In the Po Valley we opt for the most resistant, if possible, and choose a sheltered location. The ideal is to place them near a wall facing south. The preparation of a thick mulch is essential. Small plants can be covered with a double or triple layer of non-woven fabric or transparent plastic. Alternatively it is possible to cultivate in large pots to be moved in a cold greenhouse during the winter.

How to plant the Phormium

Planting can be done in autumn (in areas with mild winters) or in spring (in northern regions).
How to proceed?
They are usually found for sale in pots.
We work in depth the soil to make it soft and airy. If it is too compact, remove it and incorporate a good quantity of leaves, sand and a few handfuls of well-seasoned manure. On the bottom of the hole we prepare a thick gravel-based drainage layer. Insert the plant so that the collar is at the same level as when it was in a vase. We compact with the remaining soil and we irrigate, continuing assiduously for at least the first month, in the absence of rain.

Crop care

• It is necessary to remove the old leaves at the beginning of spring (or possibly cut them all at ground level, so that they are completely renewed).
• From the beginning of the season to the autumn, to stimulate growth, it is advisable to distribute a balanced fertilizer for green, liquid or granular slow release plants.
• Every two to three years it is essential to proceed, at the end of winter, with the division of the clumps, whether the plant lives in full ground or that it lives in pots. In particular, intervention after flowering is necessary. The tufts that have flowered, in fact, perish in a short time and it is good to eliminate them in order to let the younger ones grow, created around them.
• We always check that the surrounding soil is well mulched, especially in summer: this will help keep the roots fresh, spreading water supplies.