Tree Climbing Gear Procurement by NParks in Gebiz

Quotation no. / Reference no.: NPB000ETQ19300154 / NPB000EAR19301614

INVITATION TO QUOTE FOR TREE CLIMBING GEARS USED FOR WORKFORCE SKILLS QUALIFICATIONS (WSQ) COURSES BY THE CENTRE FOR URBAN GREENERY AND ECOLOGY (CUGE)

ISA Certified Arborist Prepatory Programme (Singapore) and ISA Certified Arborist Application (US and Other Countries)

About 8 years ago, it was acceptable to have a diploma in arboriculture or equivalent, plus 2 years of relavent experience in order to be accepted into the ISA Certified Arborist Prepartory Programme (see Table 1). This is programme is a series of classes facilitated by the National Parks Board in Singapore, which a candidate could go through before taking the exams to become an ISA Certified Arborist. Taking the classes could increase the chances that the candidate would pass the exams. Fast forward 5 years, around year 2017, the prerequisite changed to that of a two-year degree in arboriculture plus two years of practical experience. How many people in Singapore would have such a degree and even if one had the inclination to attain it, one would have to obtain it overseas. As for the four-year degree "in a related field" - what would constitute as related?

Table 1. Comparison between the requirements in 2012 and prerequisites in 2020 for the entry into Singapore's ISA Certified Arborist Prepartory Programme.

In the US and other countries, their statutory boards does not organise prepartory programmes for potential ISA certified Arborists, but rather the country Chapters, associate organisations or interest groups. ISA just administer the applications, exams and certification. It has stated the eligibility of candidates who wish to apply for the exam (see Table 2). Almost the same as the Singapore requirements, ISA require degree holders to have either a two-year associate degree with 2 years practical experience or four-year bachelor degree with 1 year practical experience. But what is lacking in the Singapore requirements is the "Assessment-Based Certificate Programs (Diplomas, Certificates)" category. "900 hours of assessed training" could be roughly 1 year of full-time study/training, and 1800 hours of assessed training could be roughly 2 years of full-time study/training.

Is the ISA Certified Arborist Prepartory Programme in Singapore leaving out candidates who do not have two-year or four-year degrees?

Table 2. Comparison between the eligibility to apply for the ISA Certified Arborist exam and prerequisites in 2020 for the entry into Singapore's ISA Certified Arborist Prepartory Programme.

Avocado Trouble Shooting

A homeowner planted three avocado trees on his property, and his are the only avocado trees in his neighbourhood but they are not fruiting. The varieties are Hass, Gwen and Pinkerton, as he is after the flavour and had a aversion to green skinned varieties. The trees were flowering as usual, and the foliage were green and does not show signs of drought stress.

Avocado trees have perfect flowers meaning the male and female parts are in the same flower, so Dendro's assistant was wondering if it could self-pollinate. Dendro explained that the male and female part are not active on the same tree at the same time, a flowering behavior known as synchronous dichogamy. There are two types of varieties: A-varieties that open their flowers as female in the morning and as male in the afternoon, and B-varieties that open their flowers in a vice-versa manner. During the male phase, the stamen is upright and during the female phase, the stamen lays flat around the stigma.

The detectives observed that the client's trees are A-varieties, as their visit was in the afternoon and the stamens are all upright. The three varieties planted by the client were determined to be A-varieties, and cannot fruit without B-varieties around. Dendro explained that more A-varieties are cultivated but B-varieties are necessary to pollination.

Hence, if the client wishes for his trees to bear fruit, he would have to plant B-varieties like Bacon, Fuerte or Zutano. A new breeding program from the University of California is evaluating two new B-varieties - 'Nobel' and 'Marvel' - that produces a black, Hass-like fruit.

Additional reading: Arpaia, M.L., A.E. Fetscher, and R. Hofshi. Avocado Flowering Basics. University of California Agriculture & Natural Resources. http://ucavo.ucr.edu/Flowering/FloweringBasics.html

Arboriculture's Transition into a Profession

The August 2019 edition of Arborist News had an article on the history of arboriculture and how it became a profession for arborists, but I am not going to summarise the part on history. But I do want to touch on the character below.

John Evelyn, an Englishman, published  "Sylva or, a Discourse of Forest Trees" in 1664 and called for increased tree planting and restoration of woodlands to ensure the nation's economic wellbeing. So just you know that certain country leaders were not the first to have that idea. Mr Evelyn at that time observed that tree pruning practices are poor and thus trees were full of defects. He advocated that pruning to "avoid the bark and branch tearing" and "avoid cuts close to the bole".

The author of that article (Shane A Lanigan, Chartered Arboriculturist) recalled in the 1971 being taught to make flush-cuts in order to "prevent fungal infection" and facilitate "fast and complete wound occlusion". It took Alex Shigo with books published in the 1990s and early 2000s to teach modern arborists to cease flush-cutting.

This recommendation was often forgotten, and it seemed that our industry education and standards have advanced and regressed at the same time.

Flush-cuts of tree, photo taken on Jan 2012.

Another angle of the same flush-cuts, photo taken on Jan 2012.

Back to the USA. From the early 1920s, the practice of arboriculture florished and in 1924, scientists and practitioners came together for the first 'Shade Tree Conference'. Shade tree is a "code name" for ornamental trees. An organisation not unlike a society was formed and named National Shade Tree Conference (NSTC) in 1928. In 1946 the NSTC created a fund for research and members presumably benefitted from the research. In 1961, the organisation changed its name to the "International Shade Tree Conference" and in 1976, it became the International Society of Arboriculture (ISA). Certification of arborists was first offered in the USA in 1992.

The "Certified Arborist" programme was made available in Singapore I believe in 2005, which was facilitated by the National Parks Board (NParks). After almost 15 years of seeking scientific knowledge from this esteemed society and scientists from elsewhere, I think that NParks and its arborists had made a positive impact in general on the trees under their care.

Getting the Point of Ceiba speciosa and Ceiba pentandra

Dendro the detective decided to visit a friend who was managing a rather tropical garden. The friend is an arborist and he planned to climb up a Ceiba speciosa (Brazilian silk floss tree) to do crown cleaning of some deadwood for aesthetics. The detective looked up the crown with his binoculars and handed it to his friend to have a look too. There were thorns on the branches and upper trunk, but no thorns from ground level to about 12 meters up. If the arborist had anchored his climbing line on one of the thorny branches, it could be disastrous. Thorns seemed to be an adaptive feature in Ceiba speciosa to deter damage by browsing animals when the trees are in juvenile stage. As the tree gets older, the thorns could weather off. The arborist made a note to himself to take some time to look at the upper scaffold branches with binoculars before deciding to climb or not. In this case, he decided to rent an aerial lift.

Ceiba speciosa (Brazilian silk floss tree)

Silk Floss Sky View. Photo by www.flickr.com/photos/tinyfroglet

Silk Floss Tree. Photo by www.flickr.com/photos/tinyfroglet

Ceiba pentandra (Variegated), Variegated Kapok tree at Gardens by the Bay - The lower trunk on the left seemed to be devoid of thorns but the right still have some thorns.

 Same variegated species at Hortpark - thorns still present on lower trunk.

On the upper trunk and branches as well.

Signage of the tree at Hortpark.

 Some species of Ceiba in the Flower Dome of Gardens by the Bay.

A non-variegated Ceiba pentandra (Kapok tree) at Gardens by the Bay. Appeared to have no thorns anywhere but some bumps though.

 

 A Ceiba of unknown species with menacing thorns on the lower trunk at Singapore Botanic Gardens. In the vicinity of the dry/cactus garden.

Changi Airport Interior Trees

 Interior landscape like the above gets changed from time to time according to the holidays or themes. The plants and trees would get some time in an outdoor nursery to take up natural sunlight when they are not on display.

 But how about trees that are permanently planted indoors like this Heteropanax fragrans (Fragrant Aralia). Taken on 12 Nov 2017 at T4 presumably shortly after opening.

Same tree after almost two years. Taken on 19 Sep 2019.

 Another tree of the same species looking deprived of sunlight. It had some artificial lighting to help it, although its not much help.

 Ficus benghalensis (Indian Banyan) looking balanced even though one side is facing natural sunlight.

 Ficus maclellandii (Alii Fig), which I mistakened for Ficus celebensis (Weeping Fig) initially. One side of the tree seemed to have more leaves than the side facing away from the natural sunlight.

 The tree was topped at some point to prevent the apex from hitting the false celling.

I did not get the name of this tree despite the name tag being on the tree. Does not look like Heteropanax fragrans or Ficus species. Still looking good presumably due to the natural sunlight from the clear roof.

Specialised Palm Fertilisers (Part 2 of 2)

Another possibility that palms may suffer from nutrient deficiency is that too high or low in soil pH may cause some nutrients to become unavailable to plants. There are pH probes and pH testing kits out there to find out.

Nutrient availability according to soil pH, with the optimum for plants in general being pH 6.2-7.3 (Source: https://ucanr.edu/sites/Salinity/Salinity_Management/Effect_of_salinity_on_soil_properties/Effect_of_pH_sodicity_and_salinity_on_soil_fertility_/)

For palms, the pH range for optimum availability of nutrients is even more narrower, between pH 6.5 and 7. Of course, there should also be organic matter in the soil. Soil organic matter (SOM) serves as a reservoir of nutrients, water retention, structure stability, cation exchange, regulate pH and bind SOM to soil minerals.

Here are some palm fertiliser products that I came across. Product names are changed to protect the innocent or otherwise.

1. "Migo" Palm "Food" - contains magnesium, iron and manganese. Other micronutrients are unknown. The shaker version is NPK 8-2-12 and Palm "Tree Food" version is NPK 8-4-8. 

2. "Rigo" Palm and Fern organic fertliser is 6-1-1-4 (4 refers to Sulphur as Sulphate, and also contain 1.3% Calcium). Contains blood and bone. In alkaline soil, Calcium carbonate  in the blood and bone will further increase the pH of the soil and reduce availability of N, P and most micronutrients. "Natural" sulphate of Potash is... mined from naturally occuring potash deposits in Europe. Not high anough potassium and other micronutrients it needed.

As a side note, a fertiliser could still be considered organic even if it contains mined potash (potassium). As a side side note, the name "potash" came from the phase "pot ash", which is how farmers obtain potassium a long time ago. They burn logs in clay pots to obtain its ashes, and spread it in their fields - hence the name potash.

3. "Higo" slow-release palm fertiliser has 15-15-15+2Mg plus "trace elements"... and works well with a "booster" liquid. If it is comprehensive enough then why would it need an add-on booster? 

4. "Sigo" is the one of the most complete and honest fertiliser suitable for palms and it is actually an Osmocote (slow-release) product, which says on the label that its for "Pots, Planters and Indoors". It clearly lists down the analysis, which contains nutrients that are essential for palms - K, Mn, Mg, and B.

Nutrient analysis:

N - 15.3%

P - 2%
K - 12.6%

S - 9.8%

Ca - 0.3%

Mg - 0.3%

Fe - 0.2%

B - 50mg/kg (0.005%)

Cu - 125mg/kg (0.0125%)

Mn - 150mg/kg (0.015%)

Mo - 50mg/kg (0.005%)

Zn - 38mg/kg (0.038%)

 

 Nutrient analysis of the Osmocote product - "Sigo"

A similar controlled-release fertiliser with very different nutrient analysis - "Bigo"

Turns out that palm do not need much phosphorous. Higher amount of micronutrient does not mean better for plants. Nutrients not absorbed by the plants and held by the soil will be leeched away. And that might pollute groundwater, streams and lakes.

Specialised Palm Fertilisers (Part 1 of 2)

Fertilisers for palms are specialised in the way that there was supposed to be nutrients that they need more than other type of plants included in the formulation. The palm fertilisers are supposed to have higher amounts of K, Mn and B, and I would add Mg and Mo as well. Some say Fe... but I am not too sure but let's say it should be included as well.

Table 1. Macronutrients and selected micronutrients that should be in fertilisers that claimed to be specialised for palms, and their mobility within plants and soil.

The nutrients and functions in plants are listed as follows (Source: CPH course notes, 2019)

Nitrogen - Component of nucleic acids, DNA, RNA, proteins, hormones, enzymes and chlorophyll

Phosphorus - Component of nucleic acids, ATP, DNA, RNA... The highest levels of P in young plants are found in tissue at the growing point. As plant matures, most P moves into the seeds, fruit or both.

Potassium - Maintenance of ionic balance in plant cells, operation of stomata, help plants adapt to environmental stresses (e.g., higher drought tolerance, better resistance to fungal diseases and insect pests).

Potassium deficiency in Caryota palm (Source: http://idtools.org/id/palms/symptoms/factsheet.php?name=Potassium+Deficiency)

Magnesium - Key component of chlorophyll, enzyme activation.

Magnesium deficiency in Phoenix palm (Source: http://hort.ifas.ufl.edu/nutdef/report19_Mg-MG.shtml)

Boron - Key component of cell walls and formation of pollen tubes, involved in movement of carbohydrates in pants, enzyme synthesis.

  

Boron deficiency causing bent crown and truncated leaves in palms (Source: http://shadetreeexpert.com/palm-trees/)

Iron - Component of enzymes, needed for chlorophyll synthesis, enzyme activation (nitrogen fixation is effected by enzymes called nitrogenases).

Manganese - Involved in photosynthesis to free oxygen from carbon dioxide.

Manganese defiency causing leaves to appear frizzled (Source: https://www.palmtreepassion.com/mineral-deficiency-in-palms.html)

Molybdenum - Protein synthesis, need for nitrogen fixation for nitrogen-fixing bacteria

Molybdenum deficiency in Brassica leaves causing a "whiptail" appearance, no palm leaf example (Source: https://www.pthorticulture.com/en/training-center/role-of-molybdenum-in-plant-culture/)