Parajubaea - Palms with Altitude

An in-depth look at all the species in this exiting genus, slowly becoming more widely available.
by Imtiaz McDoom-Gafoor, London, UK
Chamaerops No.33 Winter 1998/99, published online 26-09-1999

Left: Parajubaea torallyi var. microcarpa, near Potosi, Bolivia, at about 3200m.
Right: Parajubaea sunkha, near Vallegrande, Bolivia, at about 2500m.

There are three species of this beautiful, high altitude palm from South America growing in the mountain ranges of the Andes in Ecuador, Bolivia and Colombia. They are Parajubaea cocoides, Parajubaea torallyi and Parajubaea sunkha . Although rarely grown outside their natural habitat, they offer the possibility of growing another pinnate leaf palm in the milder parts of western and southern Europe which are not subject to temperature extremes.

P. cocoides is grown in Colombia and Ecuador between 2500 and 3000 m. elevation. It is only known from cultivated sources and is possibly a cultivated form of P. torallyi. The cool Andean climate sees little seasonal variation in temperature throughout the year with day temperatures barely into the low 20's c., and frosts occur at night. In Britain it has been grown to a 3 ft seedling which succumbed to -5c (24f) in a London garden. However, it has survived -8c (18f) in both Italy and northern California but was completely defoliated so perhaps its lowest endurance is somewhere between these two levels.

P. torallyi is widespread in Bolivia growing between 2700 and 3400 m. elevation. It is considered the hardiest of the three species as it originates in a climate with more distinct seasonal variation in temperate than Ecuador and also grows at a higher elevation. The climate regularly sees lows of -7c (20f) in the Bolivian Andes during the July and August winter months. Growing in sandstone mountains at the unbelievable altitude of up to 3400 m makes this the highest elevation palm in the world! It is possibly faster growing than cocoides but is still rarely grown outside of South America.

Some similarities are found between cocoides and torallyi such as habit. They both have smooth and tall stems, long petioles and regularly arranged leaflets. There are also two forms within the torallyi species - P. torallyi var. torallyi and P. torallyi var. microcarpa, which differ in both fruit size and the shape of the endocarp. They are restricted to steep inter-Andean valleys where they grow amongst spiny vegetation between 2700 and 3400 m. elevation. Here they are separated by several mountain ranges and influenced by distinctive climatic conditions. A third species was described as recently as 1996 - Parajubaea sunkha. "Sunkha" refers to the abundance of fibres the palm produces which the local people use for many purposes such as making rope and baskets. It grows in dry valleys in semi-deciduous forests also in Bolivia at the lowest elevation of the three species, 1700 up to 2200 m elevation. It is unlikely to be in cultivation anywhere outside its natural habitat and very little is known about it.

The potential of Parajubaea - particularly P. torallyi - in a cool temperate climate such as mild coastal areas of Britain and Ireland influenced by the Gulf Stream, northern Spain or parts of western France lies in two areas. Firstly, its appearance gives this palm an elegant, tropical look. The feather leaves are graceful, wispy and arching, shiny green above, greyish white beneath, on a tall, very slim trunk resembling Cocos nucifera, the coconut palm, to which it is related. It is also related to Jubaea chilensis from Chile which is reflected in its name - Parajubaea . More importantly, it has a degree of frost tolerance, especially the Bolivian species, which have a more leathery texture, perhaps an adaptation to its colder environment.

The two biggest problems are firstly getting hold of seeds and secondly germinating them. Cocoides seeds have been available before and appear regularly in seed catalogues but torallyi is much more difficult to obtain although the Seed Service does offer them occasionally. The next problem is germinating them - they have a low germination rate. It can take anything from six months to several years.

The seeds of torallyi are extremely large and heavy - bigger in size than an extra large walnut shell with three distinct ridges. P. torallyi microcarpa, has much smaller, smoother seeds with only faint ridges. The hard outer shell - the endocarp - contains the endosperm from which the seedling germinates. It is important to leave the whole seed, if fresh, in a warm, dry place for at least two months before even attempting germination. This allows the endosperm to loosen from its tough, outer shell and aids germination. The seeds can be soaked in a weak fungicide for two days and then placed just below the soil surface in a loose, open mixture, kept moist in a warm place. It is also possible to break the endocarp with a hammer or file down the extremely hard, wrinkly shell, making several wedges in it to allow moisture to enter it to aid germination. However, be warned that the hammer method may damage the endosperm if the blow is too hard as I discovered myself with several crushed seeds flying everywhere, which I promptly ate! The endosperm looks and tastes like the flesh of a miniature coconut with a sweet, pleasant taste and it is indeed often found for sale in the open markets of Ecuador.

My P. torallyi seeds took about a year to germinate. They are currently growing in a mixture of pure horticultural sand, bark chippings and perlite in containers measuring six inches diameter by sixteen inches depth - that's not a typing error, the containers really are that deep. This is because once the seeds germinate they send out a strong, penetrating taproot that goes directly downwards before top growth commences. It is important that the seedlings have a deep root run and as such specialised container sizes are almost impossible to obtain, I'd visit a hardware store and buy some plastic drainpipes. These are then cut to the length required, with a bottom made up with drainage holes and filled with an extremely free draining but moisture retentive mixture.

Apart from its unsuitability for container culture due to its need for an unimpeded root run, the single root system does not regenerate if damaged so it should never be transplanted once planted out. However, this has to be weighed against its vulnerability as a seedling in a cold climate and therefore a three or four foot plant might be a good size to plant out, with winter protection should prolonged freezes threaten.

Another limiting factor to successful cultivation outside its natural habitat is excessive summer heat, and especially hot or humid nights - day temperatures of 32c (90f) would be too high. This palm is not adapted to tropical or sub-tropical climates where it will rot and decline rapidly. The key is cool night temperatures, which is crucial to strong, vigorous growth. It should be grown in fertile, well-drained soil in full sun from an early age but must be carefully acclimatised.

Once it germinates that's most of the battle won. It grows remarkably fast and is easy to look after - not prone to any pests - the seedling fronds are tough and leathery. Since germinating each of my P. torralyii seedlings has produced three, lanceolate leaflets. One robust seedling measured 2 ft long but only 2 ins wide after only 12 months growth. Growth stopped indoors in late October with decreasing light levels but they start showing signs of growing again by early February. Its origins in a cool climate is evident by its willingness to grow during the nights and in the cold spring when temperatures are low. It is a pleasant change to see a palm growing fast when others like Sabal or Syagrus only really start growing when it is very hot.

Growth occurs rapidly after about three years, especially if planted out and freed from the restrictions of pot culture. Cocoides flowers and fruits after only twelve years in such diverse countries as New Zealand and Italy, underlying its adaptability to Mediterranean type climates. I've seen both cocoides and torallyi growing indoors as young plants in the temperate house at Kew Gardens. They looked identical although labelled differently. In general terms it is possible to identify which species your seeds are by examining the ridges on them. Both sunkha and cocoides have less obvious ridges on the endocarp. Torallyi var. torallyi seeds have three prominent ridges while var. microcarpa has three inconspicuous ridges.

A small Parajubaea is also planted outdoors at Kew in the Duke's garden although it is very difficult to see in summer, as there is a big, leafy tree in the way. It is easier to see in winter as the tree is deciduous. It survived last winter's mild temperatures without damage, helped by an extremely protected position between two brick walls.

Parajubaea may never be available commercially in Europe. The lack of seed, coupled with its erratic and lengthy germination, and its dislike for pot culture, makes it an unsuitable choice for nurseries demanding fast moving product lines. Purchasing seeds will probably remain the best way to gain access to such a tropical looking palm. It is another of those new, experimental palms from high altitude mountain ranges of the world like Caryota 'himalaya' and Ceroxylon - not yet assessed in colder climates but all requiring similar growing conditions, that can endure moderate frost, can thrive in cool summers and are highly ornamental.

 

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