Why is my tree fern dead?

Before I start, I am going right back to basics. Why? Because there is a difference between knowing and understanding. Knowing why your tree fern has died is one thing - too cold, too dry or both. But understanding how this has killed off your precious, and usually expensive tree fern will prevent you from the ignominy of having to explain why that ugly, dried out trunk is doing 'pride of place' in your garden.

You could be unlucky and find that your tree fern has been attacked by some catastrophic fungal infection. But lets face it, it is unlikely and if you do have an fungal disease it has probably taken hold because the plant has become weakened. Tree ferns are tough, if they weren't then they wouldn't have survived the past 80 million years.

Dicksonia antarctica
Firstly, and tree ferns aside, put your hands up if you can tell me how many tree species can survive if you cut their roots off?

Secondly, how many regular ferns can survive if you cut their roots off?

Ignoring all those wiseacres who mentioned mistletoe - which still has a root system otherwise it would fall off its host tree - the answer is none. So why do so many of us believe that tree ferns are perfectly capable of surviving, in fact thriving without roots? This is probably down to our perception of the plant when we first purchase one. Tree ferns have had their root system sawn off when they are imported to our country and yet we witness with our own eyes that they are still capable of throwing up strong shoots from the crown - a miracle indeed!

How is this possible? Well, within the fibrous trunk there is a series of thick tap-roots that run from the crown of the plant, down to the base of the plant. Because the original thick head of foliage has also been removed to prevent these roots from drying out during transportation, there is enough water and carbohydrate in these internal tap-roots to power out one last round of fronds.

Typical garden centre specimen
Of course, watering both the crown and the entire length of the trunk will allow the root system to take up the necessary amount of water required to survive, but don't forget that without an complete and operating root system you are going to need to water the trunk in this way up to three times a day. Even more if you have positioned your tree fern in full sun!

The next issue is nutrition. How many times have you seen tree ferns kicking around your local plant retailer with stunted and pale green fronds. Too many in my experience. Look at any images of tree ferns in their natural environment and you will see thick, dark, luscious green foliage. Look in the garden centre - and perhaps even your garden - and you will see something that looks like a neglected, yellow bonsai on a stick. So what has gone wrong? It goes back to the root system and watering. Without a soil based root system the tree fern is unable to take up the macro and micro nutrients that it requires to grow. No nitrogen, no chlorophyll, no growth.

Unfurling tree fern frond
Therefore it is not enough to water regularly, you need to feed regularly too. If you are forgetful than place a small handful of controlled release fertiliser - such as osmocote - in the crown. If not, water the tree fern with a water soluble fertiliser such as Miracle-gro. There is no harm doing both.

Get this right and your tree fern will have enough water and fertilizer to support itself until it has regrown a root ball large enough to support itself without your help.

Back to overwintering. I am not going to go into the details of how to protect tree ferns over winter as this has already been covered in a separate article. However, I will say that if your tree fern is relatively new and still without an effective root system you will still need to water during warm spells. Forget this and you can still end up with a dried out husk when you remove your winter protection. In my northern European garden I have a habit of removing the protection during the day when it is reasonable warm so that I can water and then replace the protection before nightfall.

For related articles click onto:
Grow Tree fern Seeds
How to Grow Painted Ferns
The Devil's Hand Tree -  Chiranthodendron pentadactylon
What is Air Layering?
When do Tree Ferns put out New Fronds

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