PURPOSE:  To identify trees from their winter twigs using dichotomous keys.

MATERIALS: Twig samples, hand lenses, metric rulers, winter tree key(s).

INTRODUCTION:  Seed plants are divided into two classes.  The flowering plants (Angiosperms) produce their seeds inside an ovary.  Most northern Angiosperm trees are deciduous since they shed their leaves in the fall. Gymnosperms produce their seeds in cones.  Most of the Gymnosperms in northern latitudes are conifers.  With one exception, conifers are evergreen since they retain their needles throughout the year. In winter, you can identify tree species by careful examination of their twigs, just as you can in summer using leaf characteristics.

PROCEDURE: 

A.  Obtain winter twigs from several species of evergreen and deciduous trees commonly found in your area.

B.  Divide your samples into two groups:  Gymnosperms and Angiosperms.

C.  Select one of the Gymnosperm twigs that has needles.  Observe the size, shape, and color of the needles, and their attachment to the twig.

D.  Select one of the Angiosperm twigs and examine it closely with a hand lens.  Compare the twig with the diagram to familiarize yourself with twig characteristics.

E.  Use the dichotomous keys to identify all the twig samples and record the information on the data table.  The key will help you determine the distinctive characteristics of each.

QUESTIONS:

1. What is the basic difference between evergreen and deciduous trees?

2. What is unusual about the tamarack (larch) tree?

3. What are some of the characteristics that help you identify different genera of conifers?

4. What are some of the characteristics that help you identify different species of pines?

5. What are some of the characteristics that help you identify species of deciduous trees?

6. What kinds of deciduous trees have opposite leaf arrangement?

7. How can you distinguish between a terminal bud and an axillary bud?

8. What is the function of bud scales?

9. What is the function of lenticels?

10. Briefly describe two ways to tell the age of a woody twig.

WINTER TWIG DATA SHEET

1A.  Leaves present; tree evergreen.........................................go to 2
1B.  No leaves present; tree deciduous......................................go to 9
.
2A.  Leaves scalelike, overlapping..........................................go to 3
2B.  Leaves needlelike, not overlapping.....................................go to 4
.
3A.  Twigs flattened, fan-like.....................White Cedar (Thuja occidentalis)
3B.  Twigs rounded or 4-angled.............Eastern Red Cedar (Juniperus virginiana)

4A.  Needles in clusters....................................................go to 5
4B.  Needles occurring singly...............................................go to 7

5A.  5 needles/cluster...................................White Pine (Pinus strobus)
5B.  less than 5 needles/cluster............................................go to 6

6A.  Needles more than 12 cm long.........................Red Pine (Pinus resinosa) 
6B.  Needles less than 12 cm long....................Scotch Pine (Pinus sylvestris)

7A.  Needles flat...........................................................go to 8
7B.  Needles angular....................................White Spruce (Picea glauca)

8A.  Needles stalked, on woody cushions..................Hemlock (Tsuga canadensis)
8B.  Needles stalkless, leaving round, depressed scars..Balsam Fir (Abies balsamea)

9A.  Spur shoots present as enlarged bumps where clusters of 
	needles were once attacked........................Tamarack (Larix laracina)
9B.  No spur shoots; leaf scars with axillary buds or bud scars present....go to 10

10A. Leaf scars opposite (2/node)..........................................go to 11
10B. Leaf scars alternate (1/node).........................................go to 13

11A. Terminal bud large (more than 2 cm), dark and sticky............Horse Chestnut
							   (Aesculus hippocastanum)
11B. Terminal bud not as above.............................................go to 12

12A. Leaf scar with crescent-shaped bundle scar......White Ash (Fraxinus americana)
12B. Leaf scar with several separate bundle scars......Sugar Maple (Acer saccharum)

13A. Stem "Knobby" with large nodes..................Cottonwood (Populus deltoides)
13B. Stem not knobby; nodes not greatly enlarged...........................go to 14

14A. Stem yellowish; axillary buds persistent and
	 flattened to the stem....................Weeping Willow (Salix babylonica)
14B. Stem and buds not as above............................................go to 15

15A. Terminal buds long (1-1.5 cm) and pointed...American Beech (Fagus grandifolia)
15B. Terminal buds less than 1 cm..........................................go to 16

16A. Buds clustered at end of twigs........................Red Oak (Quercus rubrum)
16B. Buds single, not clustered at ends....................................go to 17

17A. Twigs bright green...............................Sassafras (Sassafras albidum)
17B. Twigs not bright green................................................go to 18

18A. Buds and twigs red, or greenish red...................................go to 19
18B. Buds and twigs brown, not red.........................................go to 20

19A. Buds lopsided...............................American Basswood (Tilia americana)
19B. Buds rounded, not lopsided.......................Black Cherry (Prunus serotina)

20A. Leaf scars entirely surrounding the bud........Sycamore (Platanus occidentalis)
20B. Leaf scars not as above..........................American Elm (Ulmus americana)

Western Conifer and Deciduous Trees

1A.  Leaves present, tree evergreen..........................................go to 2
1B.  No leaves present, tree deciduous.......................................go to 7

2A.  Leaves scalelike, overlapping...........................................go to 3
2B.  Leaves needlelike, not overlapping......................................go to 4

3A.  Twigs flattened, fan-like.....................Western Red Cedar (Thuja plicata)
3B.  Twigs rounded or 4-angled.........Rocky Mountain Juniper (Juniperus scopulorum)

4A. Needles in clusters......................................................go to 5
4B. Needles occurring singly.................................................go to 6

5A. 2 needles/cluster, 2.5-8 cm lo...................Lodgepole Pine (Pinus contorta)
5B. 2 or 3 needles/cluster, 10-18 cm long...........Ponderosa Pine (Pinus ponderosa)

6A. Needles flat.................................Douglas Fir (Pseudotsuga taxifolia)
6B. Needles angular..............................Englemann Spruce (Picea engelmanni)

7A. Leaf scars opposite (2/node).............................................go to 8
7B. Leaf scars alternate (1/node)...........................................go to 10

8A. Leaf scars with crescent-shaped bundle scars..Green Ash (Fraxinus pennsylvanica)
8B. Leaf scars with several separate bundle scars............................go to 9

9A. Young twigs green........................................Boxelder (Acer negundo)
9B. Young twigs not conspicuously green............Bigleaf Maple (Acer macrophyllum)

10A. Stem "knobby" with large nodes.........................................go to 11
10B. Stem not knobby, nodes not greatly enlarged............................go to 12

11A. Buds slightly hairy.......................Plains Cottonwood (Populus sargentii)
11B. Buds smooth..............................Black Cottonwood (Populus trichocarpa)
 
12A. Hairy buds clustered at end of twig................Bur Oak (Quercus macrocarpa)
12B. Smooth buds not clustered at twig ends.................................go to 13

13A. Buds usually stalked....................................Red Alder (Alnus rubra)
13B. Buds not stalked.......................................................go to 14

14A. Each bud enclosed in a single cup-shaped scale.................Peachleaf Willow 
								(Salix amygdaloides)
14B. More than one bud scale enclosing each bud.............................go to 15

15A. Buds flattened to the stem..................Quaking Aspen (Populus tremuloides)
15B. Buds not flattened to the stem..................Paper Birch (Betula papyrifera) 

with Annotated Alphabetical Species List

1A.  Tree deciduous; spur shoots present as enlarged bumps where
	needles were once present.............................................Larix
1B.  Tree evergreen; leaves present as needles or scales on winter twigs....go to 2

2A.  Leaves scalelike and overlapping; or both scalelike and needlelike.....go to 3
2B.  Leaves needlelike only, not overlapping................................go to 7

3A.  Leaves single..........................................................Sequoia
3B.  Leaves in pairs, threes, or fours; scalelike...........................go to 4

4A.  Twigs flattened, fan-like..............................................go to 5
4B.  Twigs rounded or 4-angled............................................Juniperus

5A.  Leafy twigs distinctly longer than broad............................Libocedrus
5B.  Leafy twigs about as long as broad.....................................go to 6 

6A.  Leafy twigs 2-3 mm wide..................................................Thuja
6B.  Leafy twigs about 1 mm. wide.....................................Chamaecyparis

7A.  Needles in clusters......................................................Pinus
7B.  Needles occurring singly...............................................go to 8

8A.  Needles 2-ranked (one row of needles on each side of twig).............go to 9 
8B.  Needles extending from all sides of twig..............................go to 11

9A.  Needles stalked, on woody cushions....................................go to 10
9B.  Needles stalkless, leaving round, depressed scars........................Abies

10A. Needles flattened, sharp pointed.........................................Taxus
10B. Needles 4-angled, blunt pointed..........................................Tsuga

11A. Needles flattened..................................................Pseudotsuga
11B. Needles 4-angled.........................................................Picea

ANNOTATED ALPHABETICAL LIST OF NORTHERN CONIFER TREE SPECIES

Abies amabilis(Pacific Silver Fir)needles dark green above, silvery white below, 
								up to 3 cm long
A. balsamea (Balsam Fir) - dark green needles up to 3 cm long
A. concolor (White Fir) - pale blue green needles, up to 6 cm long
A. grandis (Grand Fir) - dark green needles, up to 5 cm long 
A. lasiocarpa (Alpine Fir) - blue green needles up to 4.5 cm long
A. magnifica (California Red Fir) - blue green needles up to 4 cm long
A. procera (Noble Fir) - blue green needles, up to 3.5 cm

Chamaecyparis lawsoniana (Port Orford Cedar) - slender, flattened twigs
C. nootkatensis (Alaska Cedar) - 4 angled stout twigs
C. thyoides (Atlantic White Cedar) - scalelike leaves flattened in 2 rows

Juniperus occidentalis (Western Juniper) - leafy twigs stout; "berry" bluish black
J. osteosperma (Utah Juniper) - leafy twigs stout; "berry" brownish
J. scopulorum (Rocky Mountain Juniper) - leaf twigs slender; "berry" bright blue
J. virginiana(Eastern Red Cedar) - leafy twigs slender; "berry" dark blue

Larix laricina (Tamarack) - needles 2-2.5 cm long
L. occidentalis (Western Larch) - needles more than 2.5 cm long

Libocedrus decurrens (Incense Cedar)

Picea engelmanni(Engelmann Spruce) - blue green needles; disagreeable odor when crushed
P. glauca (White Spruce) - blue green needles; twigs without hairs
P. mariana (Black Spruce) - pale blue green needles; twigs hairy
P. pungens (Blue Spruce) - dull blue green needles
P. rubens (Red Spruce) - dark green needles; twigs hairy
P. sitchensis (Sitka Spruce) - dark green, flat needles

Pinus attenuata (Knobcone Pine) - yellowish green needles, 3 per cluster,  8-18 cm long
P. banksiana (Jack Pine) - dark green, 2 per cluster, 2-4 cm long
P. caribaea (Slash Pine) - dark green, 3 per cluster, 20-30 cm long
P. contorta (Lodgepole Pine) - yellow green, 2 per cluster, 2-5 cm long
P. edulis (Pinyon) - dark green, 2 per cluster, 2-4 cm long
P. flexis (Limber Pine) - dark green needles, 5 per cluster, 5-9 cm long
P. jeffreyi (Jeffrey Pine) - blue green needles, 3 per cluster, 13-26 cm long
P. lambertiana (Sugar Pine) - blue green needles, 5 per cluster, 8-10 cm long
P. monophylla (Singleleaf Pinyon) - gray green, single, 3-13 cm long
P. monticola (Western White Pine)- blue green needles, 5 per cluster 5-10 cm long
P. ponderosa (Ponderosa Pine) - dark green, 3 per cluster, 10-18 cm long
P. resinosa (Red Pine) - dark green, 2 per cluster, 5-6 cm long
P. rigida (Pitch Pine) - dark yellow green, 3 per cluster, 8-16 cm long
P. sabiniana (Digger Pine) - pale blue green, 3 per cluster, 20-30 cm long
P. sylvestris (Scotch Pine)- blue green, 2 per cluster, 4-6 cm long, twisted
P. strobus (Eastern White Pine) - blue green, 5 per cluster, 6-13 cm long
P. virginiana (Virginia Pine) - gray green, 2 per cluster, 5-8 cm long, twisted

Pseudotsuga taxifolia (Douglas Fir)

Sequoia gigantea (Giant Sequoia) - scalelike leaves, 5 cm long
S. sempervirens (Redwood) - needlelike leaves up to 2 cm long

Taxus brevifolia (Pacific Yew) - needles in 2 rows
T. canadensis (American Yew) - needles extending out all sides of twig

Thuja occidentalis (Northern White Cedar) - yellow green leaves flattened in 2 rows
T. plicata (Western Redcedar) - dark green leaves flattened in one plane

Tsuga canadensis (Eastern Hemlock) - dark green needles averaging 1.5 cm long
T. heterophylla (Western Hemlock) - dark green needles averaging 2 cm long
T. mertensiana (Mountain Hemlock) - blue green needles up to 2.5 cm long

1A. Tree with evergreen leaves..............................................go to 2
1B. Tree deciduous, no leaves present on winter twig........................go to 5

2A. Leaves aromatic when bruised.......................................Umbellularia
2B. Leaves not aromatic.....................................................go to 3

3A. Twigs bright red with smooth, peeling bark..............................Arbutus
3B. Twigs reddish brown; bark with thick or squarish plates.................go to 4

4A. Winter buds one or none.............................................Castanopsis
4B. Winter buds three or more...........................................Lithocarpus

5A. Leaf scars and buds opposite or whorled.................................go to 6
5B. Leaf scars and buds alternate..........................................go to 12

6A. Terminal bud absent.....................................................go to 7
6B. Terminal bud present....................................................go to 8

7A. Leaf scars often whorled, pith solid....................................Catalpa 
7B. Leaf scars opposite; internode pith chambered or hollow...............Paulownia

8A. Leaf scars broad and conspicuous........................................go to 9
8B. Leaf scars narrow or inconspicuous; bundle scars usually three.........go to 10

9A. Bundle scars separate, usually 5 or more...............................Aesculus
9B. Bundle scars appearing as a curved, oval, or C-shaped line.............Fraxinus

10A. Buds scales 2...........................................................Cornus
10B. Buds scales more than 2...................................................Acer

11A. Thorns or spines present..............................................go to 12
11B. Thorns or spines absent...............................................go to 14

12A. Terminal bud present.................................................Crataegus
12B. Terminal bud absent...................................................go to 13

13A. Spines unbranched, usually in pairs at nodes...........................Robinia 
13B. Spines with 2 to many branches.......................................Gleditsia

14A. Bud scales one........................................................go to 15
14B. Bud scales more than one..............................................go to 19

15A. Stipule scars present.................................................go to 16
15B. Stipule scars absent..................................................go to 18

16A. Stipule scars encircling the twig.....................................go to 17
16B. Stipule scars not encircling the twig....................................Salix

17A. Terminal bud present..................................................Magnolia
17B. Terminal bud absent...................................................Platanus

18A. Leaf scar large, irregularly heart-shaped; terminal bud present....Gymnocladus
18B. Leaf scar broadly crescent or horseshoe shaped;
					terminal bud present................Asimina

19A. Bundle scar one.......................................................go to 20
19B. Bundle scars more than one............................................go to 21

20A. Bundle scar a transverse line, terminal bud present; twig aromatic...Sassafras
20B. Bundle scar C-shaped, terminal bud absent;twig not aromatic..........Diospyros

21A. Terminal bud present..................................................go to 22
21B. Terminal bud absent...................................................go to 33

22A. Stipule scars present.................................................go to 23
22B. Stipule scars absent..................................................go to 29

23A. Stipule scars nearly or completely encircling twig....................go to 24
23B. Stipule scars not encircling twig.....................................go to 25

24A. Bud scales 2......................................................Liriodendron
24B. Bud scales 10 or more....................................................Fagus

25A. Bud scales numerous in 5 rows; buds clustered at end of twig...........Quercus
25B. Bud scales usually 2-6, not in rows...................................go to 26

26A. Lowest bud scale directly over leaf scar...............................Populus
26B. Lowest bud scale not directly over leaf scar..........................go to 27

27A. Buds usually stalked.....................................................Alnus
27B. Buds not stalked......................................................go to 28

28A. Twigs with bitter almond odor...........................................Prunus
28B. Twigs with wintergreen odor.............................................Betula

29A. Pith with transverse partitions or thickenings........................go to 30
29B. Pith homogeneous, without transverse partitions or thickenings........go to 31

30A. Pith brown; scales of terminal bud lobed...............................Juglans
30B. Pith white; scales of terminal bud not lobed.............................Nyssa

31A. Axillary buds more than one..............................................Carya
31B. Axillary buds solitary................................................go to 32

32A. Inner bud scales with hairs.............................................Sorbus
32B. Bud scales usually 6, without hairs, often twisted.................Amelanchier

33A. Stipule scars present.................................................go to 34
33B. Stipule scars absent..................................................go to 35

34A. Axillary bud one.....................................................Ailanthus
34B. Axillary buds more than one.............................................Cercis

35A. Pith with cross partitions..............................................Celtis
35B. Pith homogenous, without cross partitions.............................go to 36

36A. Buds not symmetrical.....................................................Tilia
36B. Buds more or less symmetrical.........................................go to 37

37A. Bud scales two or three...............................................Castanea
37B. Bud scales four or more...............................................go to 38

38A. Bud scales in two rows, about six visible................................Ulmus
38B. Bud scales not in two rows............................................go to 39

39A. Bud scales in 4 rows, about twelve, without vertical lines............Carpinus
39B. Bud scales about 6, spirally arranged, with vertical lines..............Ostrya

ANNOTATED ALPHABETICAL LIST OF COMMON NORTHERN DECIDUOUS TREE SPECIES

Acer negundo (Boxelder)- opposite leaf scars meet to form a tooth-like point
A. nigrum (Black Maple) - rough, hairy twigs
A. pensylvanicum (Striped Maple) - short stalked buds
A. platinoides (Norway Maple) - green marked buds; wide angled fruits in pairs
A. pseudo-platanus (Sycamore Maple) - large green buds
A. rubrum (Red Maple) - rounded bud scales
A. saccharinum (Silver Maple) - pointed bud scales
A. saccharum (Sugar Maple) - brown buds on slender twigs
A. spicatum (Mountain Maple) - densly hairy twigs

Aesculus glabra (Ohio Buckeye) - keeled bud scales with fine hairy edges
A. hippocastanum (Horse Chestnut) - terminal bud dark, sticky, more than 2 cm long
A. octandra (Sweet Buckeye) - bud scales not keeled

Ailanthus altissima (Tree of Heaven)

Alnus rugosa (Speckled Alder)

Amelanchier laevis (Allegheny Serviceberry)

Asimina triloba (Pawpaw)

Betula lutea (Yellow Birch) - yellow peeling bark; slight wintergreen flavor
B. lenta (Sweet Birch) - dark brown, not peeling bark; strong wintergreen flavor
B. papyrifera (Paper Birch) - trunk with peeling white bark
B. populifolia (Gray Birch) - catkins usually born singly at twig ends

Carya cordiformis (Bitternut Hickory) - terminal bud more than 12 mm with dark scales
C. glabra (Pignut Hickory) - twigs and buds smooth, lateral buds nearly at right 
					angles to twig
C. tomentosa (Mockernut) - terminal bud nearly round, hairy

Carpinus caroliniana (American Hornbeam)

Castanea dentata (Chestnut)

Catalpa speciosa (Catalpa)

Cercis canadensis (Eastern Redbud)

Celtis occidentalis (Hackberry)

Cornus florida (Flowering Dogwood)

Crataegus douglasii (Black Hawthorn) - thorns 2 cm long
C. pedicellata (Scarlet Hawthorn) - thorns 5 cm long

Diospyros virginiana (Persimmon)

Fagus grandifolia (American Beech)

Fraxinus americana (White Ash) - horseshoe shaped leaf scars
F. pennsylvanica (Red Ash or Green Ash) - very dark buds
F. quadrangulata (Blue Ash) - 4-sided twigs; smooth trunk

Gleditsia tricanthos (Honeylocust)

Gymnocladus dioica (Kentucky Coffee Tree)

Juglans cinerea (Butternut) - leaf scars topped by a velvety strip
J. nigra (Black Walnut) - lateral bud in notch of leaf scar

Liriodendron tulipifera (Tulip Tree)

Magnolia grandiflora (Southern Magnolia)

Nyssa sylvatica (Black Tupelo)

Ostraya virginiana (Hop Hornbeam)

Paulownia tomentosa (Foxglove Tree)

Platinus occidentalis (Sycamore)

Populus balsamifera (Balsam Poplar) - very long, resinous buds
P. deltoides (Eastern Cottonwood) - buds sticky
P. grandidentata (Bigtooth Aspen) - buds dusty-gray, and divergent from twig

Prunus americana (American Plum) - thorn-like twigs
P. pensylvanica (Pin Cherry) - buds clustered at tip
P. serotina (Black Cherry) - lenticels horizontally elongate
P. virginiana (Choke Cherry) - lenticels round to oval

Quercus alba (White Oak) - smooth twigs; rounded buds; stemless acorns
Q. bicolor (Swamp White Oak) - twigs smooth, with rounded buds; long-stemmed
						 	acorns 
Q. coccinea (Scarlet Oak) - red-brown twigs, top-shaped acorns, rings around 
							top of acorn 
Q. macrocarpa (Bur Oak) - twigs somewhat hairy, with rounded hairy buds
Q. muehlenbergii (Chinquapin Oak) - light bark; pointed buds with hairy scales
Q. palustris (Pin Oak) - cone-shaped buds
Q. rubra (Red Oak) - saucer-shaped acorn cup
Q. velutina (Black Oak) - grayish wool on bud scales

Robinia pseudoacacia (Black Locust)
Salix amygaloides (Peach-leaved Willow) - twigs yellow to yellow-brown; large 
							buds; U-shaped leaf 
S. babylonica(Weeping Willow - twigs yellow or orange, slender and weeping
S. nigra (Black Willow) - twigs dark brown

Sassafras albidum (Sassafras)

Sorbus americana (Americana Mountain Ash) - smooth twigs
S. aucuparia (European Mountain Ash) - wooly twigs and buds

Tilia americana (American Basswood)

Ulmus americana (American Elm) - twigs soft hairy
U. rubra (Slippery Elm) - twigs hairy and rough
U.thomasi (Rock Elm) - twigs corky winged