Growing Phormiums in Pots With Full Planting Guide

Last Updated on April 9, 2024 by Real Men Sow

Phormiums, the exotic-looking evergreens that look like swords, are easy to grow. These plants are great for containers, gravel gardens, and sunny borders. They are an eye-catching feature with their curious, striking flowers that tower above mature clumps in the summer.

How To Start Growing Phormiums In Pots

Choosing Phormiums

The height and color of Phormiums is what makes them so popular. Some forms, such as Phormium Sundowner and Phormium Tenax Purpureum Group, have an upright growth habit. These plants can reach more than 2m (6 2/3 feet) in height. You can plant them at the border. Other forms, such as Phormium Platt’s black and Phormium ’Jester’, have arching leaves that grow to 1.2m (4ft). They are great for border highlights and container plantings. They form slow-growing clumps which make them great for focal point planting and gravel gardens.


Most plants are hardy for the average UK winter, but it is possible to damage your plant in colder winters or in northern areas of the UK. Mulch and wrapping can help prevent this. You should check the label to see the hardiness of the plant. Some plants, like Phormium “Duet”, can be affected by low temperatures. Others, like Phormium Tenax Purpureum Group, can withstand temperatures up to -10°C.

Buying phormium plants

You can buy container-grown plants all year. To ensure that the plant is appropriate for your garden, check the label to see the height and spread. Even though they can be sold as small plants at first, phormiums will quickly grow to a large clump over a few years.

Planting Phormiums In Pots

When to plant phormiums

Phormiums are not hardy so it is best to plant in spring. This allows the plants to establish before the weather turns cold or wet. Although it is possible to plant in the summer or early autumn, late plantings are more susceptible to cold and wet damage.

Where to plant

When choosing the right spot for your plant, keep these things in mind:

  • Phormiums thrive in sunny borders that are protected from the prevailing cold winds.
  • If you live in the colder areas of the country, it is best to grow near a south-facing wall or fence.
  • Soil that isn’t prone to getting wet in winter
  • To ensure that the plant is appropriate for your situation, check its height and spread.
  • To prevent phormium leaves from smothering other plants, leave plenty of space

Soil preparation

Phormiums mostly prefer evenly moist soils, regardless that they’re drought tolerant after being established. You should improve the soil of the planting area by putting a bucketful per square meter of bulky organic matter like garden compost or a manure-based soil container

How to plant

There will be a temptation to plant them deeper to protect its base from frost damage, however, don’t give into it. Make sure to plant them at the same level when you’re going to plant them in a container.

Phormiums in pots

Phormiums are a striking plant that can be the focal point for containers because of their structural and functional properties.

  • Planting up in spring requires you to increase the size of your container each year by 5cm (2in), all around the root ball.
  • You should aim for a container size of 45-50cm (18-20in), cm in depth and width. This should be enough for cultivars that reach 1.5m (5ft) height. If larger cultivars grow, they will need a bigger container. Otherwise, they can become too heavy and may fall over during windy spells.
  • Use a peat-free multi-purpose compost without John Innes potting soil. To improve drainage, mix in perlite or fine-grained horticultural soil – about 10% volume
  • The clumps can become congested over time and may benefit from being divided in spring.  

General Care For Phormiums


  • Newly planted phormiums should be watered during dry spells (especially in summer) during their first year of life after being planted in the ground.
  • If plants aren’t growing well, they can usually withstand drought. However, it is possible to water them during extremely hot or dry conditions.  
  • Container-grown phormiums can be more susceptible to drought damage. Therefore, pots should be used regularly to ensure that the compost is not too dry.

Feeding phormium plants 

  • Apply a general fertilizer to plants in the ground like fish blood and bones after planting in spring then follow the manufacturer’s directions.
  • To encourage new growth, you can feed and mulch your plants with organic matter like garden compost or manure-based soil conditioning if they are having trouble establishing or were damaged by the harsh winter.
  • Only if they are in poor health, mature plants don’t need to be fed often.
  • Regular feeding container-grown plants from late spring through midsummer with a liquid feed is a good idea. To provide food throughout the season, you can also add slow-release fertilizer powders to the top layer of compost in spring.

Winter protection

Although phormiums can withstand most winters, they may need some protection.

  • Protect the base with mulching with a layer of 7.5-10cm (3-4in), dry mulch such as bark. Proceed to remove the mulching in spring
  • If you live in colder areas, wrap the top growth with fleece.
  • Container-grown plants should be moved to a more secure position, such as near the house wall.


Because Phormiums can be grown year-round, they don’t need to be pruned. However, older clumps may benefit from some spring cleaning.

  • Remove any winter-damaged, old or withering leaves in spring. Wear gloves and pull them by hand.
  • While you are spring cleaning, remove the flower stems from the base of the plant.
  • If they have suffered severe winter damage, don’t hard-prune clumps. Recovery may take a while.
  • Consider lifting the clumps and dividing them in spring if they become too big.


Propagation by division

By dividing the clumps of phormiums in spring, it is simple to propagate them. Split the leaf fans and roots, then pot them up. You can divide the sections into larger pieces and plant them in prepared soil.

Growing phormiums from seed

You can also grow phormiums from seeds if you are looking for a little more challenge. However, the resultant plants will likely be quite different from the parent plant in terms of shape and color.

  • Sow the ripe seeds in spring by collecting them. Simply cover the seed lightly with vermiculite/compost and store at 18°C (64°F) in a propagator.
  • Germination can take up to a year

Problem You Might Encounter When Growing Phormiums

Cold damage

Frost can cause damage to Phormium during cold winters

  • Remove all cold-damaged foliage in spring
  • Only prune the plants if they are badly damaged. To encourage new growth, feed the plants with Grow more or any other general fertilizer. Remember that the recovery may take a while.
  • Wrapping and mulching can provide winter protection.
  • You might consider moving the plant to a more suitable spot that is protected from cold winds and hard frost.

Phormium mealybug

Phormium mealybug can cause black spots on leaves (sooty mold) or white fluffy deposits at the base of leaf fans.

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.