Palms for Europe's Zone 8
There are so many palms for us to try in the temperate
areas of Europe. Don lists a dozen or so, that in his experience,
should do well here, and gives invaluable advice to help them succeed.
Don Tollefson, 599 California -Avenue, Venice, CA90291, USA
Chamaerops No.25 Winter 1996/97
Zone 8 contender: Ceroxylon quinduiense, cool growing
'Wax palm' from the Andes
USDA Plant Hardiness Zones
A system of climatic classifications based on an area's average
extreme lows (AEL's). This factor is found by dividing the sum of
yearly lows of a particular area by the number of years for which
records are available (minimum 30 years). Zone 8 relates to areas
with AEL's of between -6.5ûC and -12ûC, (10ûF to 20ûF) and, in Europe,
covers most of France, N. Spain, the colder parts of Britain and
Ireland, NW Germany, Netherlands, Belgium, coastal Norway, N. Italy
through former Yugoslavia to N. Greece.
Throughout the world, the west coasts of all of the
continents maintain a mild USDA Plant Hardiness Zone 8 climate much
farther north than their zone 8 counterparts on the east coasts
of those same continents. Incredibly this enables west coast palm
enthusiasts from the northerly most coastal tip of Europe and the
Pacific Northwest of the USA to establish palm collections as much
as 900 to 1000 miles farther south than their counterparts on the
east coasts! This phenomenon is probably due to the counter clockwise
rotation of the earth as it revolves around the sun which also results
in the west coast's comparatively dry summers with limited summer
heat, mild wet winters and frequent marine inversions as contrasted
to hot, wet, humid summers with warm nights and clear skies on the
east coasts of those same continents. With these conditions identified,
it becomes apparent that there are many likely new palm species
worthy of trial along these northerly west coasts as well as proven
Zone 8 east coast palm species that require intense summer heat
(which is lacking on northerly west coasts) by providing heat artificially.
Examples of proven east coast zone 8 heat-requiring palm species
are Livistona and Sabals.
One likely solution to the lack of west coast summer
heat is the post planting technique of installing individual cold
frames around these species until the palm is established. This
requires installation of supports wrapped with plastic which may
need to remain for two or three years, arid there is no guarantee
that the palm will continue to survive once the cold frame is removed,
but for sure, the cold frame will provide the necessary level of
intense summer heat to make that final determination. Cold frames
easily provide an increase often to twenty degrees on a sunny day,
more than enough to boost the temperature to a level which facilitates
palm photosynthesising even the most stubborn palm species. The
Zone 8 east coast species that perform without intense summer heat
should require no specific post planting techniques, although some
form of post planting technique is generally beneficial for any
Palm growing success at any location or in any climate
requires selecting correct species of palms for the climate zone,
coupled with their size and condition at the time of planting them
in the ground. In terms of size and condition, a large, substantially
root bound five gallon size (20 litre/lO" pot) is recommended.
In terms of species there are no less than thirty palm species worthy
of trying in Europe's zone 8, some of which are new arrivals, untested
as of yet while others are simply those which have not been utilised
much in the past because they require too much summer heat. Some
species worthy of trial are as follows (in alphabetical order):
Brahea armata, B. bella (=B. dulcis) and B. dulcis.
Brahea armata, B. bella and B. dulcis are perhaps the most cold
hardy of the Brahea genus. They require more summer heat than is
customarily characteristic of Europe while they are young, so they
will require individual cold frames to compensate for the lack of
summer heat. How they will do in the long run without post planting
techniques is uncertain, but they should do extremely well once
they obtain some size. They are wonderful, slow growing fan palms,
many of which exhibit blue and glaucous leaf colours, adding to
the intrigue of any palm collection.
Butia capitata. It is difficult to imagine this pinnate
palm not surviving in many parts of Europe. It prefers summer heat,
so will benefit from an individual cold frame, although it will
survive without one. They grow slowly but steadily during the cool
parts of the year so they should survive and do quite nicely once
estab lished. They are lovely palms that lend that tropical ambience
that can only be provided by pinnate frond palms and exhibit an
off-green colour which adds to the contrast of any palm collection.
B. capitata is a proven staple in other Zone 8 areas, and should
be a welcome addition to European collections.
Ceroxylon alpinum, C. quindiuense and C. ventricosum
C. alpinum, C. quindiuense and C. ventricosum are partial crownshaft,
pinnate palms which show tremendous promise for cool climates. C.
ventricosum is the only one of the three that has so far endured
the heat of Southern California, where it simply seems too warm
for C. alpinum and C. quindiuense Further north. however, in the
San Francisco Bay area, both C. alpinum and C. quindiuense grow
easily. There is no question that both will grow much farther north,
having survived as far north as they have been tried, and could
possibly survive the winters of Zone 8 Europe if someone would simply
try them. They are large, majestic palms, which have the unusual
quality of looking their best in the winter, serving as a counter-balance
to the declining of other species due to seasonal change. The problem
with these species is that seed availability is sporadic, but specialist
seed dealers and nurseries do massage to collect and distribute
seed of them from time to time and a collector could expect seed
of these species within a year from the time of request placement.
Actually, any Ceroxylon species is worthy of trial in Europe, and
it would seem that some of them would be as cold hardy, or even
more cold hardy than the three mentioned above. Several Ceroxylon
have been available over the years from both high and intermediate
elevation locales, so with a little luck and vigilance, Ceroxylon
could soon be simmering in your collection.
Chamaedorea microspadix C. microspadix is a surprisingly
tough pinnate palm in terms of cold hardiness, particularly considering
its misleadingly delicate and tender appearance. C. microspadix
have survived 3 degrees Fahrenheit (-16ûC) with little or no damage.
It's fact, there have been periodic claims that it is more cold
hardy than Rhapidophyllum hystrix. but probably not. R. hystrix
is clearly the "king of cold." C. microspadix is not a
small palm like many think. It can grow to nearly twenty feet in
height, and can create quite a large, spectacular clump of attractive
green bamboo-like stalks creating the lush, tropical ambience which
is the objective of many palm enthusiasts. C. microspadix does not
require intense summer heat to survive, but is rather content to
grow in cool conditions.
Chamaedorea radicalis C. radicalis is a delightful-looking
small palm that takes severe cold without complaint. It is comparable
in cold hardi ness to C. microspadix, but I have never heard which
of the two is officially more cold hardy. They 1)0th seem far more
cold hardy than necessary to survive in much of Europe. C. radicalis
is a welcome addition to any garden, and it will probably perform
similarly to Trachycarpus fortunei in that it will likely produce
viable seed, but in a much shorter time period. C. radicalis grows
even better thais C. microspadix in a cool climate and has known
to push new growth with practically no warmth available. There are
many other Chamaedorea species worthy of trial, but start with these
two. They are proven. Some European growers contend that C. metallica
is also quite cold hardy while others claim that it cannot withstand
temperatures colder than 25 degrees F. (4ûC).
Chamaerops humilis var. cerifera. Only recently introduced
into cultivation, "Cerifera" is the blue variety of Chamaerops
humilis Chamaerops humilis has long been a standard in many European
gardens, but the "Cerifera" variety has proven to be at
least as cold hardy as C. humilis, easily hardy enough for success
in cold locales. Imagine the addition of the new colour of this
palm into your collection.
Dypsis (Chrysalidocarpus) decipiens. D. decipiens
is a pinnate leaf palm which is almost certain to flourish in parts
of Europe. Of all the recent Madagascar entries, D. decipiens has
proved to be the most cold hardy to date. It routinely survives
temperatures in the teens (Fahrenheit) (-7 to -10ûC) showing no
signs of damage, and is more than ready to test lower levels of
cold hardiness. D. decipiens is drought tolerant, doesn't require
excessive summer heat and tolerates cold whiter rain and wind. Sound
like the palm of your dreams? It probably is. D. decipiens is also
an exciting entry for the European collector because it is an exceptional
palm in terms of beauty and size. It is a gorgeous lime green colour
with a bulbous, self cleaning crownshaft., exceeding 50 feet in
height in habitat. Imagine, a palm as majestic as a Royal, growing
in London, Valencia, Rome or the Cote d'Azur! D. decipiens has the
ability to crown Europe as what it is, a wonderful place to grow
Juania australis. J. australis is another pinnate
leaf palm known commonly as the "Robinson Crusoe palm"
from Robinson Crusoe (Juan Fernandez) Island off the coast of Chile.
It is a gorgeous, lime green, partially crown shafted palm that
grows to about 40 feet in height. There is no doubt that it will
survive far south, and probably will do just fine in much of Europe.
Side by side, J. australis has fared equally as well as D. decipiens
when confronted with cold. The problem is with obtaining seed of
this palm. The last time I can recall seed of this species being
available was when Southern California Palm Society member Brad
Carter visited Chile and Juan Fernandez Island about three years
ago, and returned with over 2000 seeds and such a story to relate
indicating just how difficult it is to obtain seed of this rare
and magnificent beauty. I would really like to see a second sponsored
excursion sending Carter back to Chile and Juan Fernandez Island
for the purpose of collecting Juania australis seed once again.
Jubaea chilensis J. chilensis should perform well
in milder parts of Europe. It has no difficulty with winter cold,
and is as cold hardy as Butia species, but will survive even lower
temperatures. Be warned that although this palm is a behemoth, it
is also a slow, slow palm in terms of growth rate. This is a palm
that you should consider as your legacy to palm cultivation.
Livistona australis, and saribus Many growers have
tried Livistona without success, but almost without exception the
Livistona species was L. chinensis This is the much more common
species, but it is not nearly as cold hardy as L. australis and
L. saribus which are almost identical in terms of cold hardiness.
Both enjoy hot summer periods, so be prepared to utilise post planting
techniques to fulfil this requirement. After they are established
they should grow slowly but steadily in cool conditions. L. saribus
has large, showy thorns and a burgundy colour to it making it quite
Nannorrhops ritchiana N. ritchiana is allegedly one
of the two most cold hardy palms, the other of course being Rhapidophyllum
hystrix. It likes heat in the summer, but does not demand it, and
performs satisfactorily in a cool climate. It is a low. clumping
palm and its most notable quality is the fuzzy brown suede-like
tomentum that forms on its leaf sheaths.
Rhapidophyllum hystrix. R. hystrix is unanimously
acclaimed as the most cold hardy palm known. It is a small palm
with the major problem for Europe being that it demands summer heat
for survival. It requires post planting techniques to survive in
many parts of Europe. R. hystrix, Nannorrhops ritchiana and Sabal
minor are palms that will survive in USDA Plant Hardiness Zone 7,
so with a little artificial heal they should survive quite nicely
Parajubaea cocoides amid P. torallyi These are beautiful
pinnate palms that could be considered long shots. In terms of cold
hardiness. P. cocoides does not fare as well as Juania australis
or Dypsis decipiens, but a metre high specimen was growing in London
until this past year when it met its demise due to an unusually
cold winter. P. torallyi has not been officially tested, although
preliminary speculation is that it is far more cold hardy and faster
growing than P. cocoides Predictable enough, right! But aside from
that, both P. cocoides and P. torrallyi are incredibly beautiful
palms, and if you can get theism, you should.
Ravenea glauca R. glauca is a gorgeous small pinnate
palm from the highlands of Madagascar, reaching heights of 10 to
20 feet. It has survived temperatures in the low 20's F. (around
-5ûC) as a seedling. in USDA Plant Hardiness Climate Zone 9a. Additionally,
it showed no damage whatsoever, and in view of this, coupled with
the fact that it was merely a seedling at the time of this exposure,
strongly suggests that R. glauca is a very serious candidate for
growing attempts in colder climate zones. If it does survive. bear
in mind that there are other palms that grow in the same highlands
of Madagascar and might possess similar cold tolerance.
Sabal etonia, S. mexicana, S. palmetto and S. minor.
S. minor is the most cold hardy species of this genus of cold hardy
palms. All Sabal are worthy of an attempt in Europe, but for certain,
try S. minor. Sabal demand intense summer heat, something that is
characteristic of all Sabal and perhaps more so than any other genus.
and something that is in short supply in most of Europe. Therefore,
success will require post planting techniques. Always remember that
Once these plants are established with post planting techniques
they should continue to grow, albeit slowly, and always remember
that "Sabal may grow slowly, but time passes quickly".
Trachycarpus martianus T. nanus. T. takil and T. wagnerianus
Trachycarpus species have long been a staple of European palm collections,
and any Trachycarpus species is worthy of trying and should stand
a high probability of surviving. In England. there has been success
with all of these species. The superb thing about this genus is
that it does not require summer heat to thrive, and if anything,
grows best in cool summer areas. In short. it is perfectly suited
for most of Europe. They are also ideal in that they can endure
a substantial almost of winter cold and rain while they are young.
making it possible to raise them in a semi-protected position without
going to the trouble and expense of a greenhouse or some similar
growing environment. However, we must never lose sight of the fact
that the goal is to grow beautiful, exotic tropical-looking palms
outdoors year round. and not to discover which palms are the easiest
and most convenient to grow. This - has already been done so if
we have to exert a little extra effort to succeed with new palm
species it is well worth it.
Trithrinax acanthocoma T. brasiliensis and T. campestris
These three are surefire growers for Europe. They are by no means
overly elegant, but they lend a complimentary tropical look when
grown in combination with Trachycarpus fortunei that far surpasses
the look provided by two or three T. fortunei alone. In fact one
of the favourite conditions which advanced palm enthusiasts consistently
identify is the look provided by several different palms species
grown in proximity with one another, in preference to the look provided
by several palms of the same species grown in proximity with one
another. To obtain this look it is imperative to discover new palm
species that will survive and look good in European palm collections
and the genus Trithrinax is in the same category as the genus Trachycarpus
in that they are easy and convenient to grow there, probably not
even requiring a greenhouse.
A couple of final notes. It is most important to remember
that the best palm size for planting outside in the ground is a
substantially root bound five gallon (20 litre/10" dia. pot).
'Substantially root bound' means more roots than soil upon removal
from the container, and the root and soil mass is almost like a
block of concrete. The most common error committed by an enthusiast
is to cheat a palm out of its pre-planting preparation by planting
it before it is ready, and when it is too small to respond to the
trauma of being transplanted from a container into the ground, and
then unable to withstand the rigours of the first winter. The most
horrifying expansion of this error is doing so with a non-rootbound
palm in which soil falls off its roots as it is removed from the
The other thing to remember is that with individual
cold frames, a palm that requires intense summer heat can obtain
a reasonable size in two or three years, rather than the twenty
or thirty years without an individual cold frame. This is not a
typing error, heat makes an incredible ten fold difference and an
individual cold frame provides that heat and once a palm obtains
a reasonable size, it will no longer require the same level of heat
to maintain that same level of growth so it will grow beautifully,
even though its cold frame has been removed. This also enables the
process of growing these species in root control bags in a cold
frame until they reach a substantial size, and then removing them
and planting them outside or transplanting them into boxes until
they are ready to be planted outdoors in the ground.
13-07-20 - 15:03GMT
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