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Dr. Frankensteins Palms - Cold Hardy Hybrids

Nigel Kembrey, UK
Chamaerops No. 46, published online 18-03-2003

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X Butyagrus nabonnandii (Butia capitata X Syagrus romanzoffiana), originally donated to Huntington Garden in San Marino, California by Dr. Merrill Willcox.
Photo by John Strazicich.

I have been an exotic gardener for approaching 15 years, having been inspired by Richard Darlow's exotic garden, which appeared on Gardener's World one winter day. I have tried just about all of the available cold hardy palms, but the only two pinnate palms I can grow are Butia and Jubaea. Butia is a wonderful palm, but is slow, putting on about five leaves a year, whilst Jubaea (my favourite palm) as we all know puts on only two leaves a year in our climate and takes forever to reach any decent size. I have been aware of hybrid palms for some time but they never seem to be available. I don't know whether this is because the purists don't want to encourage them or simply because they are rare and unobtainable. They do seem to be available in the USA for those who want them, and there are large specimens dotted around both Europe and the USA.

We are fortunate that Butia is the nymphomaniac of the palm world, seeming to hybridise readily with other members of the Butiinae subtribe. There are several Butia hybrids available to the cold hardy palm grower, each with its own set of attributes. I am by no means an expert, but have been following developments in this field with interest, enabling me to provide an overview of the different hybrid varieties as follows.

Butia X Jubaea or Jubaea X Butia. Imagine a Jubaea sized palm that grows at Butia speed and is equally as cold hardy. This particular cross works both ways with either plant able to receive pollen from the other. It is generally thought that Jubaea X Butia is the more attractive palm. This is one of the earliest hybridisations to be successfully completed and there are several mature specimens throughout the world. The plant varies but some of the better specimens tend to be Jubaea sized with recurved leaves but more importantly grow with vigour and are capable in a warm climate of producing seed after 15 years as opposed to 40 years for the true Jubaea. The seed from the Jubaea X Butia are viable and several palms throughout the world now produce F2 seed so the palms should become more readily available. The F2 seedlings tend to be quite variable. Butia X Syagrus. Also called Butyagrus or the Mule Palm. This palm grows very rapidly in a warm climate and can look incredibly beautiful. The growth habit varies considerably. The seed is sterile, hence the name Mule palm. Unfortunately the palm is a disappointment in cool climates, it proved like Syagrus to dislike our cool conditions and refused to grow. One development, though, is the discovery that Mule pollen is viable and this can be backcrossed with Butia to produce Butia X (Butia X Syagrus) and Jubaea X (Butia X Syagrus) also called X Jubutyagrus, the former will revert to a much more Butia like plant, but will hopefully retain some of the vigour and characteristics of the Syagrus whilst being more cool tolerant. There is one in Florida which Merrill Wilcox referred to as "surprisingly growing much more quickly than a dozen or so adjacent Butyagrus, but not such an attractive palm, and not as fast as Jubutyagrus". It is uncertain why these palms are faster than Butyagrus, there are many possible explanations, but the most likely is the fact that Butyagrus growth slows considerably in Florida in winter ,whereas Butias and Jubaeas do not, so it is likely that the extra injection of Butia or Jubaea genes enables the plant to grow at lower temperatures which is very promising for those of us in a cool climate. It should be pointed out that results of this cross are likely to be very variable.

Butia X Parajubaea This is a recent hybridisation, with plants only becoming available for the first time in recent months. The earliest crosses have been made with Parajubaea cocoides as there are seemingly no Parajubaea torallyi in the USA capable of producing pollen. The seedlings display remarkable vigour and will become very impressive palms I am sure. With Parajubaea growing rapidly in cool conditions, this particular hybrid has incredible potential for our cool climate, with none of the drawbacks encountered with the Butia X Syagrus. The only remaining question is its hardiness; Parajubaea cocoides does not succeed where the temperatures fall much below -3°C and one wonders just how much extra hardiness the cross with Butia will impart. I am quite sure, however, that future crosses with Parajubaea torallyi will be much hardier and will prove a huge winner in our climate.

There are also further possibilities. I know that seed from a cross of Butia X Allagoptera has recently been collected, and with Lytocaryum and Polyandrococos also members of the Butiinae subtribe, I am sure that attempts will be made to hybridise these wonderful palms in the future, which may or may not be successful. All members of this family show some resistance to cold so the prospects are good. Polyandrococos is like a dainty Ceroxylon but unfortunately very rare. There is also the prospect of backcrossing the above hybrids against Butia or other Butia hybrids in many different combinations which may also produce some further exciting palms. Sooner or later if enough pollen is thrown at enough palms, maybe a super fast and super hardy pinnate palm could be created. I know that Jubaea X Parajubaea is to be attempted in the spring, possibly the most exciting of them all!


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