Observations at HortPark (and Elsewhere) on May 2019

I am taking the Certified Practising Horticulturist course that stretches over a few weeks (taking a few days each week) over at HortPark. When I say Hyderabad Road no-one knows it, but everyone knows HortPark.

A mistletoe attached to a (once) living brach of a tree. This is showing the cross section, and the haustoria seemed to have formed a "broad-head arrow" to penetrate into its host. Note the darker cells of the mistletoe, and the lighter cells of its host.

A look from the outside. Darker bark belonged to the mistletoe, and lighter bark its host.

I was exploring on mistletoes attaching themselves onto tree earlier here.

Kerriodoxa elegans (White-backed palm), a single species endemic to Thailand. It grows as an understory palm, and thus more suitable in shade.

Butterfly gardens attract bees as well. The lesson here is not to expect one type of insect (most people prefer butterflies) and reject the presence of the other.

The Hort Lawn, where event rentals and wedding photo shoots take place. They have installed the automated mower that I mentioned earlier here.

Note that the tenant (behind the fence on the left) has moved out and there does not seem to be a new one moving in. In 2015, the Hort Lawn was overhauled (which I imagine to some inconvenience to the tenant back then). And in 2017 when I attended a Kombucha making class there, NÓNG was the tenant.

 Floating islands that was on the irrigation pond were removed. They were overgrown with Cyperus papyrus and crowding the other species out.

Floating islands at Pang Sua Pond, Bukit Panjang. No Cyperus papyrus were used here, but mostly Cyperus prolifer.

 Chonemorpha fragrans (Frangipani vine), which is a great alternative as a native climber besides Tristellateia australasiae (Maiden's Jealousy). The origin stated on the label should have read "Singapore, India, and a whole lot of other countries". The leaves looked like that of Beaumontia grandiflora (Easter Lily Vine), but its flowers looked like that of a... Frangipani.

On the way to city centre, and I saw these tree containers along the centre divider at Esplanade Drive. Plumeria rubra and Tecoma stans - great choices as they are both drought tolerant. Diagram from NParks CUGE RTN 01-2017, showing a "downsized version" of the tree container that has an inner diameter of 1.3m and height of 1m.

Containerized Technology: Long Term Observation of the Growth Potential of Container Trees, Centre for Urban Greenery and Ecology, Research Technical Note RTN 01-2017.

There was only one RTN in the year 2017, and no more thereafter.

 Palms that are usually solidary could be nice as a "cluster" palm as well.

Shown here is Bismarckia nobilis 'Silver'

 A self-sown Bismarckia nobilis 'Silver' "cluster" at a plant nursery in Muar, Malaysia. I haven't seen them self-sown in Singapore, and this might be a thing to come.

Livistona chinensis (Chinese fan palm), which is usually solidary has three "branches" here.

 

Strelitzia nicolai (White Bird of paradise) and Tacca chantrieri (Devil flower), both flowering.

Felling of Eucalyptus alba and E. camaldulensis using the "Spider" cherry picker, excavator for grubbing, and Avant loader for hauling of logs.

 

 Tamarindus indicus (Asam tree) that I had wrote about earlier here, which is replaced by a younger specimen.

Hope that the trunk collar is not buried this time.

Climbing Plants Growth Monitoring Over 3 Months

Trial done in year 2013 on true ground, on what seemed like anthropogenic clay loam soil, and covered with compost. Climbing plants were planted in two rows. Measurements over 3 months are as below.

 Row 1

Row 2

 Antigonon leptopus

Argyreia nervosa

 Beaumontia grandiflora (1)

  Beaumontia grandiflora (2) flowers

 Clitoria ternatea

 Congea tomentosa

 Ipomoea tricolor

 Odontadenia macrantha

 Pentalinon luteum (variegated)

 Petraeovitex wolfei

 Podranea ricasoliana

Quisqualis indica

 Saritaea magnifica

 Solandra longiflora

 Stigmaphyllon ciliatum

Vallaris glabra

Excerpts from Singapore’s Climate Action Plan

Nothing to do with trees and plants, but just for my record.

Two screenshots below partially bordered in cyan colour excerpted from Singapore’s Climate Action Plan: A Climate-Resilient Singapore, For a Sustainable Future (2016)
[https://sustainabledevelopment.un.org/content/documents/1549Climate_Action_Plan_Publication_Part_2.pdf]

Photos below with the exception of the two screenshots were taken by me on 13 March 2019.

It has been almost 9 years since this geobag wall was installed at East Coast Park.

 The geobag wall was observed to be undercut by wave action, and was stuffed with sand-filled polypropylene sacks, presumably a stopgap by the park management.

 One geobag heading out to the sea.

Geobag wall seemed to have terminated where there is vegetation.

A large Talipariti tiliaceum (Sea hibiscus)

 A geobag wall at another area along East Coast Park beach, adjoining a Riprap slope. Makes me wonder.

Presumably installed almost 9 years ago too.

As expected of such a hard structure, it seemed to be still solid.

Cinnamomum iners Basal Rot Disease

Cinnamomum iners (Wild Cinnamon tree) seemed to be susceptible to the basal rot disease, which cause trees to die quickly and may fail (topple) suddenly. Matured trees with above 1m in girth have been observed to be inflicted with the disease but not in younger trees.

- Yellow and/or browning leaves
- Signs of wilting
- Crown dieback
- Horizontally and vertically cracked bark on lower part of trunks and trunk flare
- Underneath cracked bark, wood is discoloured

Fungal causal agents that lead to wood rot includes:
Cytospora species, Fusarium solani, Ganoderma species, Clonostachys species, Clonostachys rosea, Gliocladium solani

Cinnamomum iners tree that was lush with healthy leaves before receiving the typical TC pruning treatment - topping off and removing almost all leaves. Shortly after, the tree seemed to have problems growing back its leaves. Most new leaves turned brown and those that did not seemed to be wilting.

 

 Cracked bark in horizontal and vertical pattern.

 

 Closer look.

   

    

Adjacent trees are growing new shoots and leaves, and no sign of cracks in the bark.

(About 3 months after the photos above were taken)

Hopea odorata sapling planted about 1.5m away from the spot where the old tree was. Hope (pun not intended) that this tree would be resistant against the basal rot fungus. Apparently it was forgottened after planting, as it was not watered and defoliation followed.

Chinese Garden - Accumulation of leaf needles at tree base

The below would be an update for this post on de-compacting a tree base:
2017: http://openplants.blogspot.sg/2017/05/accumulation-of-years-of-leaves-and.html
2018: http://openplants.blogspot.com/2018/02/accumulation-of-leaf-needles-at-tree.html

Photos below taken on 4 May 2019

 The tree (Gymnostoma nobile) that I de-compacted the tree base looks good, albeit slightly assymetrical but that tree next was... gone, presumably dead.

From another view.

 Tree base that was de-compacted on Nov 2014.

  Tree base of the presumably dead tree, which was not de-compacted. Signs of dead leaf needles still on it. Could the tree have been done in by the short drought period earlier this year and exacerbated by the compacted tree base?

Drought at SBG Eco Lake. Taken on 8 Mar 2019.

3 Diagnostics of Palms

In the Oct 2017 edition of "Detective Dendro, the diagnostic sleuth", a park manager called up the detectives because one variety of palm at her park seemed to be green and healthy, and another variety of palm had some fronds that looked yellow even with what was claimed to be optimal maintenance. Phoenix dactylifera (date palm) is dioecious (having male and female parts on seperate trees) and the healthy variety is only male. However the variety in question is female, and they had allocated magnesium to their developing fruits, and there were insufficient amount for the leaves. Solution was to prune off inflorescence stalks before fruits start to develop, or increase fertilisation rate for female palms. Use a balance, palm-specific fertiliser at a rate specified on the label, and avoid overdosing, which could induce deficiencies in other nutrients.

In the Feb 2014 edition, the detectives were called over during winter, to look at a  palm (Archontophoenix cunninghamiana) with frizzled fronds, looking like there were withered and burnt. At first, one detective thought that it was obviously due to frost damage. But the park manager shared that the skateboard area near that palm was fairly new, and another detective asked where the construction workers washed out their cement trunk. After digging around the base of the palm for a bit, chuncks of concrete were revealed. The washed out concrete raised the pH to make a more alkaline soil, and that would generally tie up manganese and iron leading to deficiency. Manganese deficiency leads to frizzling and that is commonly referred to as frizzle top. That detective asked the park manager to try a palm-specific fertiliser with at least 2% manganese in sulphate form. She suggested to fertilise the rest of the plantings with general fertiliser to lower the pH.

'Frizzle top'

In the Aug 2013 edition, the detectives were at a beach and noticed a Phoenix canariensis (Canary Island date palm) at the roadside with lots of dead fronds in the crown. The palms showed signs of being maintained as their leaf bases were pruned. However, the same palm in a private backyard does not have browning fronds. Upon closer inspection of the fronds, one-half is dead and brown while the other half is still alive and green. One detective postulated that if one of the petioles was sliced open, the vascular tissue would be dark brown with a pink blush in the surrounding tissues, indicating the presence of Fusarium oxysporum. To be sure, the detective suggested to the city arborist to send a sample to a diagnostics lab. He also postulated that the arboriculture contractor, which city arborist said quoted him low prices, was the culprit. He further shared that Canary Island date palms are very susceptible to Fusarium wilt, which is frequently transmitted through contaminated sawdust and tree sap on saws. The spots that remain on the saw between cuts are easily transmitted onto another palm. Therefore with these palms, hand saws (blades can be sterilised) should be used and not chain saws. Nothing could be done for the palms now that it was infected with Fusarium wilt, as it is nearly 100% lethal. New date palms should not be replaced on the same spot, as they would likely be contracted with Fusarium wilt from the infected soil. The detective suggests to the city arborist that he replace the palms with any other kind of palm that is not Phoenix spp., as Fusarium oxysporum is fairly host-specific.

Possibly of Decay in Trees Wounded by Decay-Detecting Drilling Devices

"The tiny drilling hole closes itself up without any damage to the tree."
- says almost everyone who have used a resistograph or IML-Resi (decay-detecting drilling devices).

A resistograph or IML-Resi is a tool for tree inspections that detect decay in trees, wooden playground equipment, utility poles, and structural wood of houses and bridges. This tool was initially developed for the tree care industry, but its uses has apparently expanded to a few other industries.

It uses a stainless steel drill needle that is 3mm in diameter (head), and 200mm to 1000mm long. When the drill needle is pushed into the tree by the device, the resistance of the wood to it is recorded on a printed graph (in older models) or displayed on a screen that is on the device. Usually two to four drill points were made at lower part of the trunk and trunk flare, and where there are signs of decay such as cavity or mushroom.

 Head of drill needle, note the brad point.

The users of this device would either say that the fibers of the wood closes the drilling hole as the drill needle was retracted, or that the drilling hole left by the drill needle is so small that it is virtually not visible. Or that the drilling hole could be covered by the tree's growth in one or two year's time. The hole may be an entry point for fungal decay, and further excabated by the wood shavings that retain moisture.

To digress a bit, bits of the wood would be sheared off to allow the drill needle to enter further. The friction between the wood and drill bit head would produce wood shavings, wear down the cutting edge, and the integrity of the drill needle as a whole [1].
To digress a bit further, a drill needle for PD-300 could cost S$30 per piece, excluding shipping.

From at least two studies, what they found did not indicate that decay-detecting drilling devices should not be used [2, 3]. Trees that were already suffering from decay within the trees had their "rot cone" extend temporarily when drilled [3]. The compartmentalising ability of the tree and the aggressiveness of the fungus (determined by inoculum potential and colonisation strategy) are of crucial importance [4]. The studies conclude that the use of invasive diagnostic devices are less serious than felling the tree, or to prune major branches and roots, which typically allows fungal decay to set in.

References:

1. Wear Behavior of Drill Bits in Wood Drilling Resistance Measurements:

E. Sharapov, X. Wang, E. Smirnova and J.P. Wacker 2018, Wear Behavior of Drill Bits in Wood Drilling Resistance Measurements, Wood and Fiber Sciences, 50(2), 2018, pp. 13

https://www.swst.org/wp/wp-content/uploads/2017/06/wfs2678.pdf

2. Development of Decay in the Sapwood of Trees Wounded by the Use of Decay-detecting Devices:

Craig Hallam 2004, Development of Decay in the Sapwood of Trees Wounded by the Use of Decay-detecting Devices, Treenet Proceedings of the 5th National Street Tree Symposium: 2nd and 3rd September 2004

https://treenet.org/resources/development-of-decay-in-the-sapwood-of-trees-wounded-by-the-use-of-decay-detecting-devices/

3. K. Weber and C. Mattheck, The Effects of Excessive Drilling on Wood Decay in Trees,
http://www.arbormedics.com/PDF/PDFsample2.pdf, last accessed 7 Apr 2019.

4. Schwarze, F.W.M.R., Engels, J. & Mattheck, C. 2004, Fungal strategies of wood decay in trees. 2nd Ed. Springer, Berlin, Heidelberg.