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 -6.5C and -12C, (10F to 20F) 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.

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 (-16C) 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. (4C).

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 -10C) 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 palms.

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 striking.

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 in Europe.

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 -5C) 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 container.

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.

 

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