A nontechnical summer key to the fifty trees

2. Leaves awl-shaped or scale-like.

3. Foliage both scale-like and awl-shaped; awl-shaped foliage particularly on young growth.

3. Foliage scale-like, spray distinctly flattened and fan-like.

2. Leaves needle-like.

4. Needles borne in clusters.

5. Needles in clusters of 2-5 (pines).

6. Needles in clusters of 5.

6. Needles in clusters of 2 or 3.

7. Needles in clusters of 3.

7. Needles in clusters of 2.

5. Needles many (more than 5) in clusters on short spur-like lateral branches; not persistent through winter; on vigorous shoots needles borne singly.

4. Needles borne singly.

8. Needles with short stems (petioles), flat, and blunt-pointed.

8. Needles without stems (petioles).

9. Needles flat, blunt-pointed.

9. Needles 4-sided in cross section, sharp-pointed (spruces).

10. Needles dark, yellowish green.

10. Needles bluish green or silvery white.

11. Arrangement of leaves opposite.

12. Leaves compound (ashes).

13. Leaflet with stems.

13. Leaflet without stems.

12. Leaves simple (maples).

14. Leaves pale green on lower surface, clefts rounded, lobes entire or with less prominent teeth.

14. Leaves white, silver or pale on lower surface, clefts sharp-angled, margins with many small teeth.

15. Leaves white or pale on lower surface, usually 3-lobed, clefts shallow and sharp-angled.

15. Leaves silvery white on lower surface, usually 5-lobed, clefts deep (particularly the middle two).

11. Arrangement of leaves alternate.

16. Leaves compound.

17. Leaves doubly compound, leaflets usually even in number.

17. Leaves only once compound.

18. Margins of leaflets entire; leaflets almost oval in shape.

18. Margins of leaflets toothed.

19. Leaflets 11-23 (walnuts).

20. Base of leaf stem with a "mustache" of hairs where it joins the twig.

20. Base of leaf stem lacking a "mustache" of hairs where it joins the twig.

19. Leaflets 5-11 (hickories).

21. Leaflets 7-11, long narrow, sharp-pointed.

21. Leaflets 5-7.

22. Upper 3 leaflets larger.

22. Leaflets of nearly the same size.

16. Leaves simple.

23. Leaves lobed.

24. Leaves palmately lobed.

25. Margins of the 3-5 shallow lobes sparsely toothed.

25. Margins of lobes entire.

26. Leaves 2-3 lobed or entire, with aromatic odor when crushed; leaf or lobe apex pointed.

26. Leaves 3-4 lobed, the apex truncate.

24. Leaves pinnately lobed.

27. Twigs with thorns.

27. Twigs lacking thorns.

28. Lobes rounded, not bristle-tipped.

29. Clefts halfway to midrib; leaves dark green above, paler below.

29. Clefts very shallow, the leaf appearing coarsely toothed.

28. Lobes with bristle tips.

30. Leaves dull green on upper side, hairy along midrib below.

30. Leaves shiny, smooth on upper surface.

31. Clefts extending halfway to midrib.

31. Clefts extending over halfway to midrib.

23. Leaves not lobed or deeply cut.

32. Leaves entire.

33. Leaves ovate or egg-shaped (when not lobed), with aromatic odor when crushed.

33. Leaves ovate (egg-shaped), lacking aromatic odor.

32. Leaves toothed.

34. Leaves doubly serrate.

35. Leaves triangular, with long tip.

35. Leaves ovate (egg-shaped).

36. Base of leaves oblique (elms).

37. Leaf surface very rough above and below.

37. Leaf surface less rough, particularly above.

36. Base of leaves even, regular, not oblique.

38. Twigs with wintergreen flavor.

39. Bark on trunk black, not peeling off in papery layers.

39. Bark on trunk yellowish, peeling off in papery layers.

38. Twigs lacking wintergreen flavor.

40. Bark scaly, scales easily rubbed off.

40. Bark smooth.

41. Bark light gray, firm.

41. Bark white, in papery layers.

34. Leaves coarsely toothed or serrate, not doubly serrate.

42. Leaves linear or lanceolate.

43. Leaves linear.

43. Leaves lanceolate.

44. Leaves coarsely toothed.

44. Leaves finely toothed, serrate.

45. Leaves broadly lanceolate, with tufts of reddish hairs along midrib on lower surface.

45. Leaves narrowly lanceolate, lacking hairs along midrib.

42. Leaves triangular, heart-shaped or ovate.

46. Leaves heart-shaped or triangular.

47. Leaves heart-shaped, nearly orbicular, the teeth many and small.

47. Leaves triangular, the teeth few and large.

48. Leaves large, blunt-tipped.

48. Leaves small.

49. Leaf base rounded.

49. Leaf base square.

46. Leaves ovate.

50. Leaves coarsely toothed, nearly lobed.

51. Leaves with teeth rounded, not bristle-tipped.

51. Leaves with teeth sharp, bristle-tipped.

50. Leaves serrate.

52. Leaves finely-serrate; twigs lacking thorns.

52. Leaves coarsely serrate; twigs with thorns.

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