Corrections to The Sibley Guide to Trees

updated 16 Oct 2009

Here are page-by-page corrections and changes for the Sibley Guide to Trees. This listing will be updated periodically as issues come to my attention. Please feel free to leave comments or send me an email if you notice anything that is not listed here.

p 3 - California Torreya, the common and scientific names should be justified left
p 28 - Red Pine needs a new name to distinguish it from Japanese Red Pine. I propose American Red Pine.

p 146 - Black Hickory caption should say "husk very similar to Pignut..."; Sand Hickory, captions should read "fruit similar to Pignut..." and "twigs similar to Pignut..."

p 179 - Tanoak - caption at bottom right should specify “pale underleaf conspicuous among dense, dark foliage”
p 189 - Southern Red Oak leafy twig, the caption saying “acorn identical to Southern Red Oak” should instead say “acorn identical to Cherrybark Oak”
p 227 - Tung-Oil Tree - leaves should be larger
p 252 - Glossy False-buckthorn includes the three leaves at the top of the column and the map at the bottom. The yellow box of text and the three leaves immediately below that are Ceanothus. The map should be moved up above the box text to make clear that it represents the range of Glossy False-buckthorn.
p255 - Rose Family Intro, near bottom of column 1 should say "Plums and Cherries (Prunus) page 256" [not page 254]
p 302 - Slippery Elm, in the third sentence "fragrant" is misspelled.
page 332 - Intro to maples, the third paragraph begins "All maples have palmately compound leaves..." This should instead say "Nearly all maples have palmately lobed leaves..." And could go on to elaborate that a few species have the leaves so deeply lobed that they are compound, and Boxelder is unique among the maples in having pinnately compound leaves.
p 345 - Mountain Maple underleaf should be rotated with stem down, (same for Vine Maple)
p 392 - First line of text - capitalize Paulownia family
p 393 - Aralia Family, add a sentence saying "Castor-Aralia (p 322) is also a member of this family and should be placed here." [and in a future edition it will be]

Index:
Pignut p 145
Rose Family p 254
And it is suggested (see comments below) that species like Northern White-Cedar and Western Redcedar should have an entry in the index under "cedar". [and presumably there are other examples like this]

Trees with opposite leaves

In the past, tree identification guides have emphasized the presence of opposite leaves as one of the most important field marks. In the Sibley Guide to Trees I used a more holistic approach, like modern bird identification, giving equal weight to all parts of the tree. A tree might catch your attention because of its flowers, twigs, bark, fruit, etc., and I don’t think it’s helpful if the field guide then asks you to check whether the leaves are alternate or opposite. It’s better to get to know all of the distinguishing characteristics of oaks and maples, for example, so that you can recognize them by multiple features, rather than having to check leaf arrangement.

In some cases, however, when you encounter a confusing tree, the presence of opposite leaves can be a useful pointer to help narrow the range of possibilities. So below I’ve put together a list of trees with opposite leaves. Interestingly, almost all of these species show up in the last 80 pages of the guide.

Definition from p xxiv of The Sibley Guide to Trees:

Leaves that grow singly from the twig, without another leaf directly across the twig, are called alternate, as they usually grow from alternate sides of the twig. Leaves that grow in pairs from opposite sides of the twig at the same level are called opposite. If three or more leaves all grow from the same level on the twig they are called whorled.

These patterns can be detected even more easily in winter, as buds and leaf scars on the twigs match the arrangement of the leaves (either opposite or alternate), and branching tends to be opposite or alternate as well. Also note that twigs with alternate leaves tend to grow in a zigzag pattern, while trees with opposite leaves generally have straighter twigs.

Species counts only include those illustrated in the guide.

North American Trees with Opposite Leaves

• Katsura, Genus Cercidophyllum (p. 101) – one introduced species [the only species in its family]
• Eucalyptus, Genus Eucalyptus (p 109) – three introduced species have juvenile foliage opposite, but adult foliage alternate [Crape-myrtle, in the same family, has alternate leaves]
• Paper Mulberry, Genus Brousonettia (p. 248) – one introduced species [other genera in the Mulberry family do not have opposite leaves]
• Lyontree, Genus Lyonothamnus (p. 293) – one native species [other genera in the Rose family do not have opposite leaves]
• Beebee Tree, Genus Evodia (p. 321) – one introduced species [related to Corktree, but other species in the Rue family do not have opposite leaves]
• Corktree, Genus Phellodendron (p. 323) – one introduced species [related to Beebee Tree, but other species in the Rue family do not have opposite leaves]
• Buckeyes, Genus Aesculus (p. 326-331) – six native and one introduced species [related to maples, but other genera in the Soapberry family do not have opposite leaves]
• Maples, Genus Acer (p. 332-351) – 13 native and ten introduced species [related to buckeyes, but other genera in the Soapberry family do not have opposite leaves]
• Dogwoods, Genus Cornus (p. 355-358) – three (out of four) native and one introduced species have opposite leaves [Dove Tree, in the same family, does not]
• Buttonbush, Genus Cephalanthus (p. 374) – one native species [the only North American tree in the Madder family]
• Ash, Genus Fraxinus (p. 376-385) – 17 native and four introduced species [all other genera in the Olive family also have opposite leaves]
• Japanese Tree-lilac, Genus Syringa (p. 386) – one introduced species [all other genera in the Olive family also have opposite leaves]
• American Fringetree, Genus Chionanthus (p. 387) – one native species [all other genera in the Olive family also have opposite leaves]
• Common Olive, Genus Olea (p. 388) – one introduced species [all other genera in the Olive family also have opposite leaves]
• Devilwood, Genus Osmanthus (p. 388) – one native species [all other genera in the Olive family also have opposite leaves]
• Desert-willow, Genus Chilopsis (p. 389) – one native species with opposite or whorled leaves [related to Catalpas, other genera in the Trumpet Creeper family also have opposite leaves]
• Catalpas, Genus Catalpa (p. 390-391) – two native and one introduced species have opposite or whorled leaves [related to Desert-willow, other genera in the Trumpet Creeper family also have opposite leaves]
• Royal Paulownia, Genus Paulownia (p. 392) – one introduced species [the only species in the family]
• Elders, Genus Sambucus (p. 397) – many native species mostly shrubs [related to Viburnums, all other genera in the Muskroot family have opposite leaves]
• Viburnum, Genus Viburnum (p. 397) – many native species mostly shrubs [related to Elders, all other genera in the Muskroot family have opposite leaves]

My latest project

After seven years of work, my new Guide to Trees goes on sale officially on September 15th (but those who live near Philadelphia can get it as early as Saturday the 12th when I'm there for book-signings). I'll be traveling quite a bit this fall to book-signings across the US and Canada, doing a variety of publicity-related things, and adding tree identification to the topics I cover here on this blog. Coming soon...

More information about the book can be found at the Knopf website, and a list of my confirmed book-signing events for the fall is here.