Russian Science

Kiril Donov writes about amazing hardy Trachy's in Bulgaria, and speculates about a dark reason for their extraordinary resistance to cold.
by Kiril Donov, Plovdiv, Bulgaria
Chamaerops No.38, Spring Edition 2000

Bulgaria is located in southeast Europe, north of Greece. I believe we have here the hardiest palm trees in the world. There are 4 trees (Trachycarpus fortunei) in the historical museum’s yard in Plovdiv. Their age is about 50 years. They produce seeds every year, and occasionally something very funny happens - they change their sex in different years. The tallest palm, a male plant, has twice changed its sex and produced seeds, but all of the seeds have been lifeless. These 4 plants are the first palms living outdoors in Bulgaria. From their seeds we have our population of Trachycarpus, surviving with no problems at temperatures below -28C (-18,4F). The absolute minimum temperature in this area is -31,5C (-24,7F). Unfortunately, the people in the museum are not very friendly; if anyone visits the museum and wants to see the palms, he will meet a stone wall. They probably hate the palms because more people visit them than the museum! One version of how the palms came to be there is that a man who used to work there planted them. However, when I visited the museum again in the beginning of November and talked to the person in charge, he said that he planted the palms in 1973. When I visited the museum for the first time in 1989 he had said that nobody knows when they were planted, and that when the Russians had come in1944 the palms were already there. So, we really do not know what is the truth. For the last10 years he has been cutting the flowers and the palms haven’t produced seeds, but last year I saw about 3000 seeds hanging on the female tree and arranged to buy all of them.

I was very surprised to see that each of the four palms grew more than1m trunk last summer. The highest palm is 7m tall and has been there for 50 years. A meter of growth is really amazing! How is this possible? Here’s my theory. The city of Plovdiv was established by trackians some 4-5 thousands years ago, before the Greek and Rome empires. It is located in Trackian lowland at150 m above the sea level. The nearest mountain is15-km away (Rhodopa Mountain). But in Plovdiv there were 7 hills, with about 350-m height. The people have already destroyed 3 of them, but the other 4 still remain like mountains in the lowland. All buildings were located on the hills. The historical museum is on one of those hills, on a huge slope. There is a big support stone wall, 3m in height, and a small place with even surface. There live the palms. The climate in Plovdiv is very dry in summer and the palms have never been fertilized nor watered, or so said the staff there. But last summer they were provided with some water, as the whole year had a lot of rain and snow. Suddenly there were weeds like trees on the field. So, it is possible that the extremely slow growth of the palms is caused mainly by the drought, as any signs of cold damage are not often seen. The soil available to them is very limited, maybe no more than a big pot. It dries out very quickly when temperatures reach 25C (77F).

I have had the same experience with my own palms. During the first years I didn’t provide any water or fertilizers in summer and they had very slow growth with small leaves. The last 2 years I made irrigation systems and they grew like crazy. Four years ago I gave a friend of mine 2 small palms, about 30cm tall, 3 years old. He planted them outside in late autumn. They survived with no problems at all. Today they have about 60cm of trunk and leaves probably bigger than the parent plants—in only 4 seasons! Those 2 palms came from seeds from the Four palms in Plovdiv. In those 4 winters they didn’t have any leaf damage, even when the temperature was -22C (-7,6F). We just didn’t have lower temperatures to test them. Last thing ... many people say that palms should not be replanted in the ground any deeper or higher than they were found. I’d like to tell you that I always do this. If the soil is not very heavy, I always plant the young palms 10-30cm deeper. In one year the plants grow over the surface again. I’ve found this is the best protection, and I’m doing it this year in my new palm nursery too. My friend planted his 2 palms more than 40 cm deeper.

Bulgaria, with an area of 42,855 square miles (110,994 square kilometers), is a little smaller than Greece. The country is divided into two parts by the east - west chain of the Balkan Mountains. The climate of Bulgaria is continental, with warm summers and cold winters. In the southern portion of the country, which is tempered by Mediterranean influences, and along Bulgaria’s Black Sea coast the winters are comparatively mild. The climate is on the whole favorable for agriculture, but it is too cold for the growing of citrus trees. The summers in Bulgaria are very hot - daytime temperature +35 to +40C (95-105F) sometimes +45C (113F). The spring is quite short (1 month) and autumn quite mild. Our winters usually bring frosts with no more than -7 to -8C (16-20F), but it is normal for temperatures to drop down to -20 to -25C (-4 to -13F) at least once. Temperatures go down below -25C (13F) at least once per three winters, and once per 5-10 winters down to -28C (-18,4F) and below, although it is very unusual for these heavy frosts to last more than a week. Temperatures have been observed to drop down to -28C (-18,4F) not less than ten times during the last 40 years. My own palms once survived very successfully at -28C (-20F) and several times at temperatures down to - 25C (-13F). Generally, however, our winters are really mild: +5 to +15C (41-59F); but, with the above mentioned exceptions, we go directly into Europe’s hardiness zone 6 and below.

It is not only my opinion that in Bulgaria we have developed a variety of Trachycarpus fortunei which could survive at lower temperatures than the original plants. All of the palms grown today in Bulgaria are produced from seeds that were produced by the palms in the historical museum’s yard in Plovdiv. I wanted to have the same success with my Washingtonias, even with my Chamaerops humilis, but all of them died during the winter of 1998/99 at -22C (-7,6F). This year I am trying to grow Sabal minor, Jubaea chilensis, Butia capitata, Phoenix canariensis, Chamaerops humilis and Washingtonia filifera outdoors with some heating. The winter frost in Bulgaria is dry. Usually there is no need to use any protection, or else the results could be worse. The only protection I use for my palms is from the wind. I put hay or straw around the trunk and that is all. Of course the protection is not applied to Trachycarpus fortunei, but to any other palm. One-year seedlings could be used for planting outdoors, or even seeds, but when using 3 year or older plants, results will be much better and faster. We suppose that there is some genetic change, because 10% of the seedlings are not able to survive at very low temperatures (D.Kozarov, Ph.D. work in 1996). (Mr. Kozarov wrote in his Ph.D. work about Trachycarpus fortunei in Bulgaria that his palms have survived -29C (-20,2F), recorded at the palms location.) Also, different plants feel frost differently. Plants that are planted at the same age, on the same day, and in the same conditions are not developing equally.

I am so sure about palm hardiness, that last year I decided to create a hardy palm nursery. It’s a kind of revolution for Bulgaria to grow palms in the open ground, but I’m growing all my palms outside after their second year of age. I grow the palms exactly like any other trees here. My nursery is located in the area of Plovdiv (4-5 km away from the city) in open field, with strong west winds and each year minimum temperatures of -20C (-4F). The absolute minimum temperature is -31,5C (-24,7F) recorded about 50 years ago. Average precipitation is 600 mm per year.

Two summers ago we had many strange things here. Many plants died at once with no reason. Other plants grew like crazy, like never before. There was a war in Kossovo, 500 km away from here. I read in newspapers that NATO used bombs containing uranium. I don’t know if the bombs caused something (our government said nothing), but my Grandmother lost the tomatoes in her garden for first time in her life (75yrs.old). I just remember that the same happened when the nuclear reactor in Chernobyl exploded. But then the tomatoes were giants.

You know, we had very close relations with the Russians, also with their science. We don’t know if our palms are the result of their science and therefore if even more incredibly hardy palms could be found there. I know that before 1956 it was an obligation for the scientists to develop subtropical plants that are able to live in our climates! In result there are many cold hardy plant species available now. In Bulgaria they tried to grow even Citrus and Date palms too, but soon gave up. The 4 original palms I mentioned could have been brought from Russia. Of course they could be from anywhere else. They also could have been developed here influenced by our local conditions. We do not know yet. But I have decided to realize my dream to see palms everywhere in Bulgaria.