Trees Please Hamilton

Green Solutions to Air Pollution

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TREE TUESDAY – Mighty Honeylocust


Honeylocust tree on Barton, ripe with seedpods

During inventory sessions we are never surprised to come across a honeylocust. In fact, over 10%, of all the trees we have inventoried are honeylocusts!

Considered a weed tree in many places, the honeylocust grows fast and is ideal for areas that are in immediate need of shade. This is why we often find honeylocusts around parking lots or beside streets. Hamilton’s Street Tree Planting Program offers the tree and its prevalence stems from tolerance to urban environmental conditions such as compact soil, salt, and drought.

Other characteristic features of this tree are its small, plentiful leaflets, and its long twisted seedpods.

The tiny leaflets are known for providing pleasant dappled shade, but are a chore to sweep up when fall comes. We are not calling the leaflets that name because they are small and cute, but because that is their official name. Each row of leaflets along a stem forms a compound leaf. On this picture below, you can easily distinguish the leaflets from the larger compound leaf.


Honeylocust leaflets and compound leaves

The honeylocust seedpods are long and twisted, containing a sweet sap for which the tree is named after. The pods are pale green until they mature in the fall to become a reddish brown. Like other trees, producing seeds is energy intensive, so it was neat to see several honeylocusts exploding with seedpod production on Barton (pictured earlier). When trees are producing seedpods, they are diverting energy away from growth of branches or trunk. Due to this, they will likely not produce large seed yields year after year.


Mature honeylocust seedpods


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TREE TUESDAY – Resilient Trees


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Trees in the Barton Centre parking lot

A struggling maple tucked away in the pavement of Crown Point’s massive Barton Centre retains few leaves. It’s barren branches stick out like accusatory fingers, “why has no one cared for me?” It is not alone. Apart from the hardy honeylocust, many of its parking lot comrades are defoliated or dead. They are isolated from the protection of other trees, and exposed to high levels of road salt, car traffic, heat and wind. Often when a new development is completed, contractors are required to care for the site’s trees for a certain period of time. We have our doubts that, by this point, the Centre’s 200+ trees are not being regularly loved. But perhaps trees are more resilient than we think? 

One way in which trees are able to survive in unfavourable conditions is to regulate their leaf temperature. An interesting National Geographic article explains how tree leaves can keep the same temperature, from tundra to tropics (link below). 

The article features a study of 39 species of trees on the North American continent by researchers at the University of Pennsylvania. These coniferous and deciduous species came from the chilly North all the way to the warm South. The study looked at the ratio of two different oxygen forms in tree rings since the specific ratio is linked to ambient temperature and humidity. Using this air temperature and humidity, they worked out the average leaf temperature of all 39 species to be around 21.4 degrees Celsius. 

The researchers believe that 21 degrees is ideal for photosynthesis, and that the trees aim to have their leaf temperature fluctuating about that point. So how do the leaves roughly maintain this temperature despite varying climates? They heat up in cool weather and cool down in hot weather by manipulating the processes of evaporation and light detection. In the heat, tree leaves bend downwards to avoid light, release water for the cooling effect as it evaporates, and reflect light with little hairs. In the cold, leaves are bunched together to reduce the rate of individual heat loss from each leaf. 


Evaporation is one way leaves can cool down in hot weather

Although many Barton Centre trees are not happy in their environment, they may try employing some of the techniques above to survive. We’re cheering them on!



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TREE TUESDAY – Significant Trees of the World

We recently stumbled across a National Geographic article highlighting the stories of many culturally and historically significant trees all over the world. From the Neem tree of India to New York City’s Pear Survivor Tree, we learn that trees are places of meeting, prayer, protest, hope, and discovery.


Mango Tree, Mozambique. Source: National Geographic

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TREE TUESDAY – What are Those Bumps on Tree Leaves?

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Hackberry Galls found on Kenilworth Trees

If you see bumps like this on your hackberry tree, do not despair! We found these strange protrusions on a hackberry tree planted beside the Barton Centre on Kenilworth. One of our volunteers said that they were caused by bugs laying eggs and feeding on the leaves. Intrigued, we investigated a bit further. 

Turns out our knowledgable volunteer was right. These galls are produced by hackberry gall psyllids – tiny grey bugs, about one tenth of an inch long. The adult psyllids lay their eggs on new springtime hackberry leaves, then the new psyllid feeds on the leaves. In response to this feeding, the tree increases production of plant growth hormone in that area, which creates the galls. These pockets form a nice protective pocket around the bugs so they can eat tree sap within the gall throughout the summer. 

Although the galls can look unsightly and cause concern, they typically do not harm the host trees. Here are a few websites with more information:

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Tree Planting at Amaolo Nature Sanctuary

The Hamilton Naturalists’ Club is hosting a tree planting at Amaolo Nature Sanctuary.  This is an unique opportunity because this sanctuary has limited public access so come check it out!
Due to the very limited parking availability, there will be a school bus charter leaving at 9:30am sharp from Dundurn Castle (look for the school bus in the parking lot)
Questions?  Email Diana at

Amaolo Nature Sanctuary Tree Planting

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TREE TUESDAY – Free Trees for Canada 150

In the spirit of Canada 150 we are giving away free trees to Hamilton residents! We’ve been strolling around the Crown Point Neighborhood delivering flyers (below) to spread the good news. 

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Often on these neighborhood walks we are reminded of the importance of our work. One Crown Point Resident was rather excited to hear about our free trees, tree inventory, and the air quality monitoring initiatives. She said that the City did not have enough air monitoring stations and that the air pollution is sometimes so bad that it makes her feel ill.

We chatted for a while about how our mobile air monitoring program is helping to fill in the gaps of the City stations’ measurements and how we are hoping to increase urban tree canopy since trees trap air pollution and carbon dioxide. We are particularly interested in giving away trees to neighborhoods around industrial areas for this reason. 

You can learn more about the work we do on this website and contact us ( to reserve your own free tree by September 8th. 


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Air Quality Update – McQuesten (III)

A third and likely final full walkthrough was completed in McQuesten.

Wednesday July 26thMcQuesten Aug 14 - 1Wednesday August 2ndMcQuesten Aug 14 - 2.pngThursday August 3rdMcQuesten Aug 14 - 3.pngThursday August 3rdMcQuesten Aug 14 - 4.pngWednesday August 9thMcQuesten Aug 14 - 5.pngThursday August 10thMcQuesten Aug 14 - 6.pngOverall Heat Map (neighbourhood boundary in black): composed of data I collected as well as previous INHALE volunteer dataHeatMap McQuesten Aug 14th.pngTree MapTreeMap McQuesten Aug 14th.png

Reducing public exposure to PM2.5 follows similar patterns to Crown Point. Dust-outs from industrial vehicles result in higher levels along Barton St. between Parkdale and Woodward Ave’s.


This problem can be mitigated through combined efforts by the City to implement more regular street sweeping and through responsible actions by the industry to mitigate it’s impact on their neighbourhood – whether that be through better paving of internal roads, washing of transport vehicles, etc.

PM2.5 levels were generally higher in the busier traffic corridors: Barton St, Queenston Rd, Parkdale Ave. Queenston and Parkdale in particular have almost no tree cover – planting trees along the sides of the road could help reduce air pollution levels.


The Red Hill Valley Parkway is actually a good example of trees mitigating vehicle pollution – the trails just west of the freeway have comparable air quality to much of the low-vehicle density areas of McQuesten.

The story is similar in the southwest gridded region of McQuesten – air quality is generally worse – this could be because of proximity to Parkdale and Queenston, but the scarcity of trees certainly doesn’t help things. OtherTreeArea4.png

Above: Looking north from Queenston Rd, the lack of trees in the southwest region is particularly apparent.

Much of Britannia Ave, as well as Glassco and Adair and the western portion of Melvin tend to be in orange – the air quality has been made considerably worse by the active road re-construction taking place this summer. Some of this is unavoidable – the use of large construction vehicles and tear-up of old road materials are currently necessary parts of road re-construction. However, the dust could be controlled better through wet cutting (using water in combination with the cutting tool) to prevent the spread of silica dust, and ripping up the road in several smaller efforts rather than all at once can reduce dust spread (less time for residents to kick it up by driving their vehicles through it, and less time for wind to carry it through the neigbourhood) and reduce resident exposure time.

A reminder that if you’re living in the lower city, particularly in Crown Point, McAnulty, McQuesten, or the Beach Strip neighbourhoods, and would like to receive a free tree for your property in September – click here.

The Trees Please team will continue meeting in Crown Point and McQuesten in the coming weeks: check out the schedule and meeting locations here.