Tree Taxonomy in Toronto

The city of Toronto has a large (> 567,000) database of the trees that live on public land. There are 246 types of trees and shrubs in Toronto, which is about one quarter of all the tree species in North America. However tropical forests win the diversity crown with tens of thousands of species.

Usually when you start to look at a new dataset its a good idea to look at its overall structure. A quick bar chart in R reveals:

Two things stand out for me. One is the long tail distribution and the other is the most common tree with over three times the number of the next most tree. This is the non-native Norway Maple that was planted in the mid 20th century to fill in the gaps left by the elm trees destroyed by Dutch Elm Disease. It turned out to be a bad replacement.

But I want to see the individual tree types so I tried a scrolling table with proportional colour bars:

Rank Common Tree Name Number
1 Norway Maple 74,668
2 Honey Locust 24,286
3 Colorado Blue Spruce 21,917
4 Crab Apple 20,342
5 Silver Maple 20,127
6 Littleleaf Linden 15,608
7 Linden 15,220
8 Schwedler Norway Maple 13,807
9 Japanese Tree Lilac 13,215
10 Red Oak 11,644
11 Sugar Maple 11,273
12 Red (Green) Ash 11,109
13 Ginkgo 10,836
14 Skyline Honey Locust 10,267
15 Austrian Pine 10,189
16 Freeman Maple ‘Autumn Blaze’ 9,644
17 Shademaster Honey Locust 9,624
18 Crimson King Norway Maple 9,603
19 White Birch 9,009
20 Kentucky-Coffee Tree 8,947
21 White Spruce 8,944
22 Red Maple 7,225
23 Service-Berry 7,138
24 Callery Pear ‘Chanticleer’ 7,040
25 Siberian Elm 6,558
26 Hack-Berry 6,055
27 Manitoba Maple 5,575
28 London Plane 4,627
29 Spruce 4,468
30 Northern Catalpa 4,443
31 Birch 4,279
32 Tulip-Tree 4,270
33 White Ash 4,085
34 Eastern White Cedar 3,951
35 Redmond Linden 3,924
36 Littleleaf Greenspire Linden 3,890
37 Columnar Norway Maple 3,762
38 Norway Spruce 3,311
39 Hedge Maple 3,274
40 Accolade Elm 3,214
41 Emerald Queen Norway Maple 3,121
42 Elm 3,109
43 Maple 3,063
44 Shubert Choke Cherry 2,918
45 Cherry 2,758
46 Bur Oak 2,699
47 Weeping White Mulberry 2,622
48 Ash 2,610
49 Sunburst Honey Locust 2,493
50 Pear 2,466
51 White Oak 2,430
52 Amur Maple 2,413
53 Horsechestnut 2,406
54 Cedar 2,403
55 Scots Pine 2,309
56 Turkish Hazel 2,258
57 Juniper 2,248
58 Apple 2,097
59 Lilac 2,035
60 Freeman Maple ‘Armstrong’ 2,000
61 European Mountainash 1,981
62 Choke Cherry 1,940
63 Mulberry 1,931
64 Saucer Magnolia 1,884
65 Horsechestnut (Ruby Red) 1,792
66 Japanese Katsura 1,746
67 Black Locust 1,744
68 White Pine 1,740
69 Bradford Pear 1,707
70 White Elm 1,662
71 Basswood 1,660
72 Royal Red Norway Maple 1,656
73 Mountain Ash 1,642
74 Yew 1,590
75 Valley Forge Elm 1,556
76 Swamp White Oak 1,543
77 Japanese Cherry 1,512
78 English Oak 1,511
79 Chinese Elm 1,393
80 Japanese Maple 1,353
81 Hawthorn 1,272
82 Plum 1,270
83 Red-Bud 1,269
84 Amur Cork 1,261
85 Tree-Of-Heaven 1,228
86 White Mulberry 1,205
87 Green Mountain Sugar Maple 1,177
88 Oak 1,164
89 European Beech 1,108
90 Douglas Fir 1,082
91 Globe Norway Maple 1,035
92 Pine 1,032
93 Eastern Red Cedar 1,019
94 American Mountainash 1,006
95 Pyramidal English Oak 982
96 Littleleaf Glenleven Linden 968
97 Ohio Buckeye 963
98 Black Locust Purple Robe 941
99 Black Maple 931
100 Balsam Fir 887
101 Black Walnut 837
102 Fir 837
103 Pin Oak 797
104 Zelkova 794
105 Iron-Wood (Hop-Hornbeam) 786
106 European Ash 770
107 Eastern Hemlock 748
108 Black Oak 721
109 Oakleaf Mountainash 721
110 Weeping Willow 667
111 Yellow Buckeye 650
112 Legacy Sugar Maple 646
113 Willow 591
114 Russian-Olive 588
115 Tatarian Maple 582
116 Peach 578
117 Bloodgood London Plane 549
118 Summit Red Ash 546
119 Scotch Elm 512
120 Butternut (White Walnut) 501
121 American Sweetgum 480
122 Poplar 464
123 Yellow-Wood 441
124 Superform Norway Maple 439
125 Ginkgo ‘Autumn Gold’ 422
126 False Cypress 419
127 Ginkgo “Columnar” 410
128 Larch (Tamarack) 410
129 Red Pine 389
130 European Copper Beech 371
131 Marshall Red Ash 370
132 Silver Queen Silver Maple 357
133 Carolina Poplar 355
134 Beech 348
135 Deborah Norway Maple 333
136 Silver Fir 313
137 Pioneer Elm 296
138 Ruby Lace Honey Locust 295
139 Cucumber-Tree, Cucumber Magnolia 293
140 Serbian Spruce 277
141 Sycamore Maple 264
142 European Purpleleaf Beech 252
143 European Buckthorn 246
144 American Beech 242
145 European Birch 238
146 European Alder 235
147 Black Cherry 231
148 Walnut 228
149 Summer Sprite Linden 213
150 Golden-Chain 211
151 Dogwood 205
152 Gum Black 200
153 ‘Autumn Blaze’ Norway Maple 190
154 European Beech “Columnar” 184
155 Freeman Maple ‘Sienna Glen’ 181
156 Chinkapin Oak 177
157 Slippery (Red) Elm 174
158 Black Willow 172
159 Rock Elm 170
160 Trembling Aspen (Poplar) 150
161 Black Maple ‘Green Column’ 147
162 Lombardy Poplar 140
163 European Hornbeam 135
164 Crimean Linden 134
165 Pink Flowering Dogwood 133
166 Black Ash 131
167 Patmore Ash 124
168 White Elm ‘Princeton’ 123
169 Cottonwood Poplar 121
170 Hawthorn ‘Winter King’ 120
171 Japanese Pagodatree 116
172 Corkscrew Willow 109
173 Freeman Maple ‘Jeffersred’ 108
174 Mophead Catalpa 108
175 White Ash ‘Autumn Purple’ 108
176 Freeman Maple ‘Marmo’ 106
177 Summershade Norway Maple 103
178 Freeman Maple ‘Celebration’ 102
179 Blue-Beech (American Hornbeam) 99
180 Japanese Yew 99
181 Dawn Redwood 90
182 Apricot 86
183 White Fir 86
184 Armstrong Columnar Red Maple 82
185 European Cutleaf Birch 79
186 English Walnut 77
187 Karpick Red Maple 72
188 Shagbark Hickory 72
189 Boleana White Poplar 71
190 Alder 70
191 American Smoketree 68
192 River Birch 68
193 Redmond Linden ’Continental 67
194 Sumach Staghorn 67
195 Purpleleaf Cherry 65
196 Hazel 63
197 Sycamore Plane 63
198 European Hornbeam Pyramidal 61
199 Pussy Willow 58
200 Black Spruce 57
201 Hickory 57
202 Yellow Birch 57
203 Grey Birch 56
204 Panicled Goldenraintree, Varnish Tree 48
205 Blue Ash 46
206 Bitternut Hickory 42
207 Siberian Peashrub 42
208 Balsam Poplar 39
209 Sassafras 39
210 European Silver Birch 38
211 Black (Red) Mulberry 37
212 White Ash ‘Autumn Applause’ 37
213 Sargent Cherry 35
214 Jack Pine 34
215 Paperbark Maple 34
216 Cornelliancherry Dogwood 29
217 Hawthorn ‘Tobas’ 27
218 Himalayan Birch ‘Jacquemonti’ 26
219 Butternut Hybrid (White Walnut) 23
220 River Birch ’Heritage 23
221 Flowering Almond 22
222 American Liberty Elm 20
223 English Elm 19
224 Halka Zelkova 19
225 Japanese Elm 19
226 Pin Cherry 16
227 American Hazel 14
228 Mountain Maple 14
229 Shantung Maple ‘Warrenred’ 14
230 Largetooth Aspen (Poplar) 13
231 Whitebeam Mountainash 12
232 Winged Euonymus (Burning Bush) 12
233 Cherry Weeping 10
234 Fall Gold Black Ash 10
235 Laurel Willow 10
236 Silver Pyramid Maple 9
237 Witch-Hazel 7
238 Silver White Poplar 6
239 Amur Maackia 5
240 Davidiana Elm 4
241 Striped Maple 4
242 European Young’s Birch 3
243 White Elm ‘Delaware’ 3
244 American Chestnut 2
245 Bald Cypress 1
246 Black Birch 1

It’s a little scrolly, but the names are clear and I like the colour bars. But there is no sense of relationships between the trees.

Then I saw that Fluorish published a treemap template. This requires a hierarchical structure, which is handy since the scientific names of trees have a hierarchical structure. Part of this name hierarchy includes Family > Genus > Species. Trees in the same genus share more in common in terms of bark, leaf, flower, seed, and general appearance than trees in different genera. With this new tree taxonomy knowledge it was super easy to create a dynamic visualization with Flourish. In the treemap, the size of each rectangle is proportional to the number of that tree species in Toronto’s tree database.

The animation is fun and informative. Some of the less common trees have unreadably small fonts which just goes to show that it’s rarely the case that one type of visualization can do everything.