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Phormium cultivation

06 Oct 2005

This page: Soil requirements - Frost protection - Propagation - House plants

 

Soil requirements

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Phormiums appear to grow well in most types of soil but, as with many other plants, a moist but well-drained soil generally gives best results. In some gardens they are planted along the sides of streams or around pond edges where they seem to grow very well. 

They grow best in a sunny position although they will tolerate a fair amount of shade. Their tough leaves are quite resistant to desiccation so in the garden they rarely need any extra watering.

For plants in containers almost any general-purpose potting compost seems to give good results. If peat-based composts are used, it is necessary to add slow-release fertiliser granules, or to feed occasionally with a liquid fertiliser.

When growing well, phormiums soon fill the pot with roots and do not apparently suffer from being pot-bound. However, for best growth it is sensible to move the plant to a larger pot when roots are seen growing out of the bottom holes.

 

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Frost protection

 

Phormiums have a reputation for being slightly tender, but in Devon we have not yet lost a plant, despite frosts which commonly reach -5C. Phormium tenax and some of its cultivars have been used extensively in gardens, public parks and along urban roadsides for many years with great success. We have seen plants of Phormium tenax growing unprotected in the far north of Scotland. (Durness)

During a frosty night the leaves of phormiums tend to curl in at the edges and become narrow and slightly twisted. As the day warms up they flatten out again. The parts most sensitive to frost damage appear to be those which were produced late in the year. Frequently, the base of the central leaf (i.e. the most recently formed part) gets frosted and the result is that this leaf collapses and dies. The older leaves are less susceptible to damage although the yellow and pink variegated types often develop brown spotting.

In our experience, the plants recover in the spring and the damaged leaves are soon replaced by new ones. Old, damaged leaves can be trimmed off once the plant is growing well.

Some of the Phormium cultivars, especially those derived from P. cookianum, are less hardy but, provided that they are not kept in small pots which can freeze solid, they will probably survive most winters without protection. In more northern areas they may need extra protection.

A well drained soil and a good mulch around the base of the plant will probably go a long way towards preventing problems. The base of the plant can be protected in the winter by covering it with bracken or straw or even a good heap of bark chips. Bracken tends to stay in position if it is intertwined between and around the leaf bases while straw may need to be held in position with netting or string pegged to the ground. Some protection can be gained by growing evergreen ground cover plants around the phormiums.

Plants in containers can be moved to a sheltered area or into a cold greenhouse for the winter or, if this is not possible, the pots can be protected by wrapping them in bubble insulation plastic or by plunging the pots into a larger container filled with bark chippings or something similar.

One wall of our house faces southwest and in the winter we stand many of our potted phormiums along this wall. During the daytime it absorbs warmth from whatever sunlight there is and we find that overnight the temperature tends to remain several degrees warmer than in more open areas.

There is always the possibility that a very severe winter could cause major damage to outdoor plants.

 

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Propagation

 

Phormiums are best propagated by division. Healthy plants soon grow into a large clump as new fans of leaves develop around the older ones. These eventually develop their own roots and can be detached from the parent plant. It is possible to cut pieces off a large plant without actually digging it up but it is difficult to do this without losing most of the roots from the cutting. It is probably better to dig up the whole plant then divide it into several pieces using a spade or knife.

Plants growing in pots can be un-potted, freed of most of the soil and small sections broken off. The roots can be carefully teased apart leaving as many as possible attached to each offset. The pieces can then be planted separately.

It is probably best to cut back some of the leaves of the young plant to reduce the water demand while it is getting established. Even if all the roots get broken off, most pieces will root again if kept moist.

 

 

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Phormiums as house plants

 

Phormiums are best grown outdoors with a free root run but small, potted plants can be used as indoor plants in a sunny window or conservatory. Under these conditions they tend to grow slowly and the colours are usually paler than normal but they do make an attractive display and contrast well with other indoor plants.

We find that the varieties with upright leaves, such as 'Sundowner' and 'Dusky Chief' do well indoors. The leaves of the arching type varieties tend to grow thinner and softer and after a few months the plant begins to look rather bedraggled.

The twisted-leaved varieties such as 'Surfer boy' have relatively tough leaves and they last well indoors.

All types are probably best brought indoors on a temporary basis and returned to the garden after a few months.

 

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