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Do you remember the tree urchin?

February 15, 2019

Back in 2012 I was amazed by the tree urchins, i.e. the fantastic red galls on Dipterocarpus tuberculatus. As it turned out, the insect responsible for this gall is indeed the aphid-related Beesonia dipterocarpi (Coccoidea) as discussed back in 2012.

A few months ago I was contacted by a research team who wanted the Dokmai Dogma gall picture for a publication. Being old and aware that my private library and photographs probably will end up in a waste bin, such a request was of course granted.

On Tuesday the article by Schultz, Edger, Body and Appel was published in Nature/Scientific Reports and contained their splendid research on the molecular biology of gall formation. In conclusion, the researchers showed that insects hijack the floral genes of the leaf cells to make a fruitlike structure which protects the insects rather than seeds.

Most cells in any multicellular organism contain the entire genome/DNA to encode the entire organism, i.e the cells of your toe have the blue prints to make your liver and brain. Since the leaf cells have the genes to make any plant structure including flowers and fruits, the insects unlock these dormant genes and start making structures resembling fruits or pistils.

How they unlock the dormant genes is still an enigma. One hypothesis is that their saliva contain plant hormones, but that would imply suitable receptors on the leaf cells’ outside membranes which seems unlikely, so it could be even more intricate, i.e. the insects manipulate the molecular locks inside the plant cell.

Is this research for nerds only? If we figure out how the insects unlock dormant genes in specialised plant cells, we might learn the trick and unlock dormant genes in specialised human cells, with huge medicinal applications such as making a new kidney or liver from your own white blood cells!

Eric Danell

Ton kwaw luang

February 14, 2019

The native orange-flowered form of Butea monosperma (ton kwaw) is the drought- and fire-resistant province flower of Chiang Mai. Its flowers are heavenly beautiful in December-January.

When I visited our beloved Dokmai Garden last July (off Butea’s flowering season) I walked past a site where I many years earlier (2007) planted a rare yellow cultivar of this monsoon species. During my years until 2013 it was always a sad looking rod with a handful of flowers, and since I did not notice it last summer I concluded it was dead. This cool season Khun Densak sent me a photograph of massive blossom in a tree so big he had to use a ladder to reach the flowers.

Last summer I apparently walked past its massive trunk without realizing it was my former shy juvenile. Many trees demand several years of establishment, and this sapling was planted in a sector which we never irrigate. The reason for selecting such a dry site was that monsoon natives do not bloom normally if their natural weather cycle is tampered with. A drought is needed for a massive blossom. It is also interesting to remember that the sad looking rod survived the overflow of the nearby quarry during the wet year of 2011, another unique feature of monsoon plants. In fact, indoor pot plants in the West are often of monsoon origin, being adapted to cope with long droughts and occasional floodings.

Huge and yellow Butea monosperma flowers are crowded on the bare branches. This is an example of a splendid ornamental for the dry garden where you save time, money and water by not irrigating. Other colourful tree species planted nearby in this dry corner are e.g. Delonix regia ‘Smather’s Gold’, Cochlospermum vitifolium, Jacaranda mimosifolia and Bolusanthus speciosus.


The old sign of the yellow Butea monosperma is now back to mark the site of a revered member of the Dokmai Garden, now twelve years of age. Its yellow flowers adorn the Dipterocarpus tuberculatus leaf litter.


Eric Danell

Santol pie

July 26, 2018

We are now back in Sweden, where an unusual drought with temperatures at 32-35 centigrades makes us feel just like home (in Thailand).

We brought back a santol fruit (Sandoricum koetjape, Meliaceae) from Dokmai Garden, where our trees grow without the need for irrigation. According to a Japanese study it is an important fruit for wild elephants in the Khao Yai National Park, and during our stay in Chantaburi province near Cambodia I saw various macaque monkeys eat the fruits. It has an interesting flavour reminding me of rhubarb, although its value as a fresh fruit is inferior to that of e.g. longan, mango and banana.

Different sources describe the fruit as a berry, drupe or capsule, indicating our limited knowledge of tropical fruits. My own conclusion after anatomical studies is that this is a fleshy indehiscent capsule where each seed is surrounded by a white and soft aril (sensu lato). This aril is difficult to remove from the seed.

I was curious if a santol dessert pie would be as delicious as a rhubarb pie. We therefore experimented with good results. The acidity of baked santol is weaker than that of rhubarb while the texture is more firm but not crispy. The reddish pieces had a meat-like resemblance.

Below is the recipe for the santol pie which we, after an initial sensory tasting, served with vanilla sauce.

1. Peel one mature yellow fruit with a potato peeler. Cut around the equator with a knife and twist the fruit so the seeds detach from one half. Remove and discard the seeds including arils from the other half. Cut the two seedless halves into thick slices.

2. Add the fruit slices to the bottom of an ovenproof dish greased with margarine.

3. Disperse 30 ml sugar and 5 ml ground cinnamon on top of the fruit.

4. Use your hands to mix 4 dl wheat flour with 200 g margarine and 30 ml sugar into a crumbly texture. Cover the fruit with this mixture.

5. Bake in the middle of the oven at 225 centigrades for 20 minutes.


Same girl and same tree 68 months later

July 20, 2018

In 2009 one of Dokmai Garden’s native pink shower saplings (Cassia bakeriana) lost its entire crown due to borers. I took the decision to cut the dead wood, leaving a pathetic stump and hope for a miracle. Three years later a new shoot had sealed the wound and replaced the crown. In the picture below my daughter Mia, at that time 8 months old, showed the position of the scar.

I thought the recovery was quite remarkable, but for how long time would the tree survive the ordeal? In the recent picture below, Mia, now 6 years and 4 months old, shows the same scar in the same tree.

So far so good! However, many trees die to faulty pruning, and even a professional cut can become infected, so this tree has been lucky.

As to the forest you see behind Mia, twelve years ago those trees were pencil-sized seedlings and all of them fit into the luggage compartment of a car. Children grow quickly!

Eric Danell

Old and new friends

July 19, 2018

So nice to meet old and new friends yesterday, representing e.g. the British Royal Horticultural Society, orchidology, plant physiology, marine biology, the Expats Club, oil industry, Thai agriculture and the Lanna Royal family. Avid gardeners from Australia, Esan, Lanna, Sweden, Switzerland, UK and USA mirrored the cosmopolitan Chiang Mai.

Since we all appreciate the rainy season the sky blessed us with a break in the rains so we could enjoy the discussions and Thai food outdoors. Absent friends may use the free app Curio xyz to home in on Chiang Mai and Dokmai Garden to see and read about some of our trees.

We thank everyone for joining!

Just back from the excursion at Dokmai Garden. From the left: Mia and Eric (Dokmai gardeners), John (New York marine biologist), Leif (board member of the Chiang Mai Expats Club), Mark (a Californian nursery man settled in Chiang Mai) and his wife H.R.H. Mae Nai (Lanna Royal family).

Organic treats from Dokmai Garden: lime (Citrus aurantiifolia), kalamondin (Citrus x microcarpa), caranda (Carissa carandas), banana (Musa acuminata (AA) ‘Gluay Khai’= ‘Sucrier’), mango (Mangifera indica) and santol (Sandoricum koetjape).

Cheers, Kate and Eric

Black bears in the trees

July 16, 2018

Upon our arrival to Chiang Mai and our beloved Dokmai Garden I noticed a multitude of large, black and hairy larvae on the trunks of our trees. They reminded me of black bears or skunks from a Walt Disney movie. The same larvae were observed in great numbers also in the nearby jungle at Opkhan and at a local tree nursery.

During my five years in Thailand I never noticed it before. I asked the manager of the nursery if she knew what they are, but she only used the northern Thai word for a caterpillar in general.

Since I was slightly worried this was a harmful pest, I began watching the larvae. The first observation was that they appeared on all sorts of unrelated tree species which is quite unusual. A tree’s chemical defence is often so advanced insects usually have to specialize in certain genera or families of trees. In this case they thrived on most trees, including e.g. mango, strychnine and golden shower from different plant families.

Secondly, the larvae did not eat leaves, nor wood, still they spent several days on the trunks of trees. A close look revealed they were actually feeding on the trunk, but not damaging the bark.

The anatomy of the larva, i.e. leg arrangement with anal claspers indicated it was a Lepidopteran, a moth. As it turns out, this larva is most likely a lichen moth, probably the diurnal Macrobrochis gigas (Erebidae).

Relieved these bear-looking larvae just feed on lichens, algae and cyanobacteria covering the tree trunks, I now enjoy their presence. The hairs are most likely irritating so I should follow the weaver ants’ precaution and not touch the larvae, but they are cute!

The reason insects some years appear in abundance is due to a fortunate combination of ideal weather and low numbers of natural predators, disease and parasitoids. A peak in population density is usually followed by years of declining numbers due to increasing numbers of natural enemies and disease.

In conclusion, there is no reason to worry. Relax and enjoy this rare moment. Soon they will grow up and fly away.

Eric Danell

See you at Dokmai Garden on Wednesday, July 18th 2018!

July 11, 2018

Dear friends of Thai flora,

At present we stay at Dokmai Garden during vacation. To catch up with friends and colleagues we invite you to a social gathering at Dokmai Garden next Wednesday, the 18th of July 2018 at 5 p.m. We offer snacks and refreshments, and Eric will demonstrate the tree app Curio xyz. Kindly let us know a day in advance if you wish to come: at

Most welcome!

Kate and Eric