The Cordyline Confusion
A short dissertation on the famous muddle between
Cordyline australis and Cordyline indivisa.
Angus White, Architectural Plants, Cooks Farm, Nuthurst, Horsham,
W. Sussex, RH13 6LH, U.K.
Chamaerops No. 3, published online 23-11-2002
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It's the Real Thing: Cordyline indivisa.
Cordyline australis is the well-known Torbay Palm,
Cabbage Tree, Tikouka, or' the one with long thin leaves coming
out of the top'. It's not a palm, it comes from New Zealand (australis
meaning southern, not Australia) and it can be seen growing in many
parts of Britain, from window boxes in Bayswater to the north coast
of Scotland. It's only reliably hardy on the Atlantic seaboard but
people have devised various cunning methods for protecting it against
severe frost so they can grow them in places they really shouldn't
be able to. They grow like weeds and despite their annoying habit
of being cut down to the ground by severe cold every few years,
are virtually impossible to kill. New shoots will nearly always
appear from the apparently dead stump and the selection of just
one (i.e. the removal of all the others) can result in spectacular
growth by the end of the growing season. Their extraordinary tenacity
to life is well documented in various anecdotes in their native
country: stories of New Zealand settlers building Cordyline Log
Cabins, going off to do a spot of pioneering, and returning to find
their home had turned into an impenetrable thicket of plants. And
of logs being washed out to sea for weeks, being flung up on the
beach, sprouting, rooting and flourishing.
So - that s the familiar Cabbage Tree we all know
- Cordyline australis. Cordyline indivisa (the Mountain Cabbage
Tree indivisa refers to its reluctance to divide after flowering)
is the close relative, also from New Zealand, that one reads about
when searching for more information about Cordyline australis. It
s always rather briefly referred to with typically dry descriptions:
'lvs. sessile, sword shaped, 6ft long, 7" wide, forming a head
12ft across' and followed by dismissive little phrases like 'only
suitable for the very mildest gardens. Somehow there's always an
unmistakable hint of a suggestion that you'd have to be pretty weird
to want a monster like that in your garden. Wrong pal - it s not
us that's weird but you who are as dull as ditchwater. Cordyline
indivisa is one of the most wonderfully spectacular and dramatic
plants that can be grown in temperate Europe and there s plenty
of evidence to show that it s as frost hardy, if not even more so
than C. australis. It appears that quite a lot of horticultural
research is done not in the field but in the pleasant surroundings
of The Royal Horticultural Society's library at Vincent Square in
London, where myths, legends and half-truths can be perpetuated
through generations of reference books and generations of people,
all quoting each other.
Being aware of its existence and little more, my
first encounter with C. indivisa was tantalizing glimpses behind
Roy Lancaster of several magnificent specimens, during a TV broadcast
from the garden at Mount Stewart in Northern Ireland. The image
of those extraordinary plants endures to this day, but attempts
at gaining more information about them was largely unsuccessful
until a visit to the garden at Inverewe in northwest Scotland in
May 1987, following the ghastly winter that walloped (i.e. killed)
most of the Cordylines throughout the country. Arriving in the car
park we were met by the horrible but by then familiar sight of soggy,
floppy, brown and smelly Cabbage Trees all over the place. And yet,
within a few paces in the garden itself, a row of perfectly healthy
indivisas. Quite clearly, in this case, indivisa had proved itself
able to withstand very low temperatures with considerably more success
than australis. Unfortunately, I was unable to find anyone to show
the remotest interest in this remarkable discovery that so clearly
contradicted all the accepted wisdom on the subject (us Exoticists
are still a tiny minority amongst plant lovers) until, later that
year, I met Roy Cheek, who was (and still is as far as I know) head
of horticultural studies at Cannington College in Somerset. He was
one of the few people I had ever met who shared the same psychological
disturbance as I - he actually liked Yuccas. Not only that, he knew
what Cordyline indivisa was and concurred with me on the subject
of its being hardier than australis and quoted one or two instances
of witnessing this rarely cultivated plant surviving frost that
had turned C. australis to spinach. He spoke of it growing at considerably
higher altitudes than australis and that common sense dictated that
it was bound to be hardier. That same year I managed to acquire
some plants from Bill Spink at the Palm Farm in Humberside. For
some reason I had it in my head that they liked the shade, so the
new plants were placed in a shady spot in the greenhouse where they
languished and died. Only later did I discover that they re hopeless
in shade and hate high temperatures!
When we started our nursery in 1988, Cordyline indivisa
was to be one of our essentials, so we imported large quantities
of seed from a supplier in Western Australia. We sowed them, they
all came up like mustard and cress, and grew at a rate that we really
weren't prepared for - alarmingly fast. Urged on by our initial
success we ordered even larger quantities of seed this time from
New Zealand. Again they all came up like mustard and cress and we
rubbed our hands with glee at the thought of all those hundreds
and hundreds of little Cordyline indivisas. The only trouble was
that they weren't hundreds of little Cordyline indivisas; they were
hundreds of little Cordyline australis. Recrimination ensued - you
sent us the wrong seed and you - native Kiwis - should be ashamed
of yourselves, can't tell the difference between a Cabbage Tree
and a Mountain Cabbage Tree. Eventually we let the whole thing drop
and acquired another lot from a third source. The suppliers were
absolutely positive that the seeds came from Cordyline indivisa
(as did the previous lot), from Hawkes Bay, no doubt about it. This
time the confusion began to reveal itself: the seeds all came from
one plant but as they grew, it was clear that about 70% were C.
australis, and only 30% C. indivisa.
During research I had done at the R.H.S. library,
I'd looked up every reference I could find to Cordylines in the
R.H.S. journal, going back to its birth in about 1840. The historical
confusion was quite clear: The plant C. indivisa was known from
Cook's second voyage in 1773 but it wasn't introduced until about
1850 when, not unreasonably, plants from seeds labelled C. indivisa
would themselves have been labelled as such, even though they looked
like C. australis - the difference would not have been known about.
It doesn't require much imagination to begin to understand how such
hideous confusion between two species could be wrought. It's also
clear that there was a certain awareness of this confusion at the
time because between about 1870 and 1900 there were several references
to a plant called 'C. indivisa (vera)' or the true Cordyline indivisa.
When you add to all this the fact that most European nurseries (from
whence cometh most plants that end up in English Garden Centres)
still sell C. australis as Cordyline indivisa (which it ain't) or
as Dracaena indivisa (which is not a valid name for anything) and
are completely unaware that there are other species of Cordyline
other than the one they call Dracaena - one begins to understand
the nature of the mighty muddle.
The cause of all the confusion then became clear:
Cordyline australis has 'dominant genes'. This means that when the
two species hybridise (which they frequently do) the progeny is
likely to display more of the characteristics of the C. australis
parent than those of the C. indivisa parent. Indeed, in our experience,
often showing virtually no characteristics of C. indivisa at all;
extremely dominant genes!
* * *
Having sorted out that particular problem, a few
general words on the subject of cultivation seems to be appropriate.
We, in the business, get a tremendous amount of
feedback from our customers about the cultural requirements of the
plants we sell. As a result of the cold spell in February this year
in particular, we've learned quite a lot more about the frost hardiness
of the Cordylines, and one thing that's apparent is the connection
between the rate of growth and their ability to withstand cold.
Slow-growing plants seem to be much hardier than fast-growing vigorous
plants. Talking this over with a number of interested people, a
trend began to emerge: those who had been eulogising about the vigour
and general wonderfulness of their Cordylines were the same ones
who were now lamenting their sad departure.
A severe frost when the temperature drops to, say,
-10¾C, can cause the centre of a Cordyline to rot. This can be prevented
by simply tying up the leaves with string, so the older leaves protect
the tender growing point. Very simple and highly effective. However,
even if that isn't done, pull out the rotten centre, give it a squirt
of fungicide (to prevent the rot from getting any worse) and, showing
its usual tenacity for life, the plant will carry on producing new
leaves, eventually recovering its perfect composure. BUT, if the
temperature falls much below, say, -12¾C, the part which is then
at risk is the not-yet-woody part of the trunk just below the leaves.
If that fleshy part is damaged by the cold, then the plant is lost,
other than its ability to grow again from the base. In cold conditions
like these, wrapping up the top part of the trunk and all the leaves
with some sort of insulating material is the only form of protection
- easy, for the resourceful Exoticist!
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