How fast do Dicksonia antarctica tree ferns grow in the UK - the saga continues

On 4 April 2014 I published a update on the growth rate of the Dicksonia antarctica tree fern in my Plymouth garden.  Two years and three growing seasons further on it's time for another update.

Measured this afternoon in now stands at 46.5 in / 118cm from ground level to the height of the growing point.

Dicksonia antarctica in the rear garden 20/10/2016

This represents a fairly moderate slowdown in growth since I last reported.  Graphically it can be represented as follows:

Dicksonia antarctica trunk growth rate in inches

Still not too bad.  There are many shrubs and dwarf conifers that can't manage this amount of height extension despite ultimately growing larger than the Dicksonia.  It can probably be explained by two factors.  Firstly trunk extension is being matched by a increase in trunk girth and this all takes energy. The fronds are larger and heavier, requiring a thicker stem for support, so the earlier growth spurt is beginning to diminish.  Secondly, watering and feeding has been reduced over the last couple of years.  I've had other preoccupations and constant attention has diminished.  Taken together, growth has slowed a little.  Still encouraging, though.  Plant a number of young (cheap!) sporeling ferns in a lightly shaded spot, nurture well and 15 years later you could have a grove of specimen plants with nearly 4ft stems and their palm like rosettes of fronds.

Dicksonia antarctica tree fern growth in the UK - an update

Three years ago I posted an entry on the growth rate of Dicksonia antarctica, the hardiest of the tree ferns.  You'll find the original here but, to summarise, I reported a growth rate of about 32in /  81cm of trunk growth in 9 years from a young, trunkless fern - with a measured rate of about 22 in / 55cm of trunk growth in the 4 years between 2007 and 2011.

Time for an update.

This morning the trunk, from ground level to the level of the growing point, measured 43in / 108cm.  Three seasons more growth have added another 11 in / 27cm in extension.  The trunk itself has thickened, with the beginnings of a broader base at ground level.

Dicksonia antarctica trunk - April 14th 2014

Slightly slower growth than previously reported, but, with four data points, it's given me a better estimate of the rate of growth of these elegant, palm like ferns.  I've revised my estimate down slightly to about 3.5-4in / 8-10cm per year.  Of course this is only based on a sample of a single plant that has spent the latter part of it's life in a fairly exposed, sunny spot.  Plants in moister, more sheltered positions in the Cornish valley gardens must have a faster growth rate.  Even so it's still quite impressive for a plant that is still very commonly advertised as growing less than 1in / 2.5cm per year.

After a few warm days the new season's growth has already started.  Here's a quick grab shot of the new fronds beginning to unroll in the centre of the trunk apex.  Poor quality but it's a bright, sunny day and worming my through the rather prickly old fronds to get a hand held shot imposed certain constraints on composition.  I'll do better when the clouds roll over and I've tidied up the dead old growth from the 2012 season.

Dicksonia antarctica fronds beginning to unroll in mid April

In the previous post I speculated that I might celebrate my 70th birthday under a crown of fronds starting above the 6ft / 180cm level. Seven more growing seasons at the revised growth rate leaves me a little short - but not by much.  I might just have to live a little longer to enjoy it.

How fast do Dicksonia tree ferns grow in the UK?

I have two tree ferns in the garden.  One Dicksonia antarctica, one D.fibrosa.  Having said that, the D.fibrosa has not yet re-emerged from it's winter defoliation so I may have lost it.  It was only small, a cheap purchase from Morrison's supermarket a couple of years back.

Dicksonia antarctica, on the other hand, came through last winter in good shape.  All the top growth was completely frosted but the trunk and new croziers survived -8C without protection.  I've  had this one for about 9 years now.  I bought it a as a tattered baby, no trunk, half a dozen fronds, discarded in an end of season garden centre sale.  £2 it cost me.  It's now considerably larger.

How much larger became fairly obvious when I cleared the dead fronds earlier this year.  It's managed about 32in /  81cm of trunk growth in 9 years.  In it's early years it wouldn't have made much growth so a better measure is gained by comparing these two photos.  The first I took in June 2007, the other this morning.

July 2007

May 2011

Roughly reckoning it's made about 22 in / 55cm of trunk growth in 4 years.  Not too bad for a tree fern that's often quoted as growing 1 in / 2.5cm per year.  OK, a sample of 1 is hardly statistically significant.  Add to that the fact that I live in a generally mild, moist area of the UK and it could be said that the growth rate is unnaturally high.  However, the plant is in a fairly exposed position, not cossetted in damp, sheltered woodland, and needs daily watering in drier weather - which should slow it down a bit.  So maybe 5-6in / 12-15cm a year isn't a bad estimate.  Which has two implications.  Firstly, if it survives I should be able to celebrate my 70th birthday under a crown of fronds that start more than 6 ft / 180cm above the ground.  Secondly, it's possible that some of the venerable plants in Cornish valley gardens aren't quite as old as everyone thinks.

Here's a photo of the whole plant.  The fronds are still unrolling so it's not quite at full extension and, with the loss of last years growth, the head isn't as full as it will hopefully be by late summer.

It's in an area of the garden that I'm now busily renovating - but it will be one of the centrepieces in the finished layout.

A final word:

Yes, I could have bought a trunked plant, unrooted or rooted.  But I didn't have the money.  At around £40 per foot a 4 ft plant (the extra would be needed for planting to ensure stability) was beyond my plant buying budget at that time.  It still is.