Gebiz ITQ for Supply of Arboriculture Equipment and Related Tools

INVITATION TO QUOTE FOR ARBORICULTURE EQUIPMENT, TOOLS, REPLACEMENT PARTS AND MISCELLANEOUS ITEMS
Quotation No.: NPB000ETQ20300010
Closed: 14 Feb 2020
Awarded: 10 Mar 2020

*highlighted in yellow in the tables below means "Awarded".

String Lights on Trees

So it was Christmas and the Detectives were invited to a friend's house. Well, in summary that friend was a Christmas decoration fiend that puts up string lights EVERYWHERE. Around the inflatable Santa, on fake Fir trees, on real maple tree branches, etc. (foreshadowing). After hanging out for a while, cue the crashing of a 15 cm (diameter) sugar maple branch onto the roof. Upon examining the broken end of the branch, the detective noticed a doughnut-shaped break pattern. A relatively smooth and discoloured outer ring made up one-third the diameter of the branch, and the middle two-third was splintered wood (at the centre).

His friend's tradition of putting on string lights and leaving them wrapped spirally around branches have predisposed them to failure. A few inches back from the break was the torn end of string lights with frayed wires exposed. But that wire was sticking out from the inside of the branch. Over time as branches grew, they became girdled, and new wood were deposited over the string lights.
However, string lights could be left up for long periods of time by attaching them vertically along the trunk or axially along the branches.

As for existing string lights completely swallowed up by the wood growth, just cut the wires flush to the bark and leave the lodged wires. If they were to be dug out, it might create an even greater problem. The friend could also - after consultation with an arborist - consider to prune off branches, which have fully impounded wires that would girdle.

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.