Last updated on April 27th, 2022
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Phormiums are very strong plants, perfect for windswept gardens and coastal areas. These are no tender houseplants and they can easily tolerate -5°C easily, even -10°C if you take some precautionary measures, such as putting a good layer of mulch around the base of plants in winter. Many people in the UK learned this the hard way in 2013 when a very cold winter killed many Phormiums in gardens throughout the UK and Ireland, however, this could have been avoided for most, although we can always learn from these past mistakes.
As previously mentioned, all they need is a lot of dry mulch around the base and in between individual shoots if you have a lot of side shoots. Having large clumps of mulch gives a degree of protection, even if this large clump of mulch gets moved about by the wind. This gives you very simple protection against harsh weather and if you learn just one thing from this growing guide, this should be it.
How to grow Phormiums
Plant in fertile well-drained soil where possible
Phormiums grow best in full sunlight but will tolerate semi-shade too. They need moist, well-draining soil. They will perform well planted in many different types of soil that are otherwise considered poor, as long as you add granular, nitrogen-based fertiliser on a regular basis during the growing season. These are very greedy plants so if you feed them well they will grow incredibly quickly.
There are many varieties and colours to choose from
You get a beautiful display of colourful foliage no matter the variety you choose, not just in the leaves but in the flowers and the seed pods once they are of a good size. The leaves have strong strips that look like colourful rainbow bands of yellows, reds, greens, and oranges running up and down, depending on the varieties of which there are many to choose from. The flowers are rich red in colour and the seed pods are hunter green.
Propagating Phormiums by division
Phormiums are so strong and hardy that you might find you want more of these plants in your garden. If this is the case you can easily propagate it by dividing a strong plant in the spring. They are probably one of the easiest shrubs to propagate and they can literally propagate themselves.
How to divide Phormiums
When you go to do this you want to dig around the plant being careful not to cut into the roots and then gently pry away the side shoots from the main clump.
You will notice the side shoots immediately because they will have developed their own rooting systems. You can easily transplant them (if they have their roots) into smaller pots such as 9cm pots, keeping them for a year in those smaller pots in a greenhouse or in a warm area with indirect sunlight such as a cold frame. Once they establish themselves you can move them back outside.
Dividing pot grown Phormiums
You can also use the same process (as above) for Phormiums grown in pots by simply removing small side shoots and potting them into their own pots. If you only have large pots you could plant two or three baby plants into one pot and they will be just as happy.
Pests and Diseases
These are so strong that they’re generally pest-free which is the good news, and those they get don’t usually cause many problems and are easily treatable.
Even rabbits seem to walk away from these plants. One thing that can happen if you have an older plant is that mealybugs can make their home around the base, however, most of the time if you grow them outside any regular birds and other wildlife that visit your garden will control the pest problem naturally.
If you are growing them in pots or containers and you have an issue with mealybugs it can change the aesthetic appeal of the plant, in which case you want to squash the bugs by hand or treat them using an insecticide.
Remember that mealybugs lay large quantities of eggs inside of the foliage so you might have to use an insecticide regularly to get rid of the issue.
No matter what, Phormiums are an incredibly easy plant to grow and you get so many colourful leaves amongst the different varieties. Anyone who lives along a coastal area and is struggling to get something growing should absolutely turn to this one and it will remain strongly in place, even surviving the UK frost. Just don’t forget to add a good layer of mulch around the base for winter, especially if the forecast is extreme like it was back in 2013.