Identifying Ash Trees

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6.1 IDENTIFYING ASH TREES

Trees are broadly distinguished from each other according to whether the tree’s leaves are op posite or alternate, and simple or compound. Using these character istics allows for the differentiation of ash from many other tree spe cies.

Twigs and branches can be used Fig. 20. An old EAB gallery that in winter to help identify trees. was walled off from the rest of Ashes (Fraxinus spp.), maples the cambium with callus tissue. (Acer spp.), catalpas (Catalpa More recent galleries surround spp.), horsechestnuts (Aesculus the old gallery. spp.), elders (Sambucus spp.), viburnum (Viburnum spp.), com the rural and urban landscape in mon lilac (Syringa vulgaris), amur Canada. It is essential that all sur corktree ( Phellodendron vey staff be able to distinguish ash amurense ) and dogwoods from other species that can look (Cornus spp.) are deciduous trees similar and be able to identify ash with buds and branches in an op trees to species. posite arrangement (Fig. 21A and B). Other tree species have buds This part of the manual is divided and branches arranged alternately into four sections. Section 6.1 pro (Fig. 21C). vides a general description of trees that are similar to ash trees Ashes have blunt buds, stout and how to distinguish ash from twigs, and an upright growth habit these similar trees. Section 6.2 with long branches. The branch provides a tree identification key tips look like tridents (3-pronged to distinguish ash trees from other fork). Bark (Fig. 22) is variable trees. In section 6.3, the distinc and thus is not a feature upon tive features of different ash spe which identification should be cies (native and many of the intro based. Maple buds are covered duced species) are described. by folded scales and the twigs are Section 6.4 provides a tree identi more slender (Fig. 23A). fication key to distinguish the ash Horsechestnuts have darker bark species from one another. Survey than ashes, large terminal buds staff should use these sections that are dark and sticky. Catalpas, together with a tree identification lilac and corktree have no true book, such as “Trees in Can terminal bud and usually retain ada” (Farrar 1995), to aid in identi seeds into winter unless they are fication. pruned off.

Fig. 21. A) Opposite branching on green ash, B) opposite twig structure on green ash and C) alternate twig structure on white elm.

In the winter, the tree species mahogany-coloured twigs, black most commonly confused with ash branch collars and larger terminal are Norway maple (Acer pla- buds than ash. The buds are a tanoides), Manitoba maple (A. distinct red colour and covered by negundo) and black walnut folded bud scales. The most reli (Juglans nigra). Norway maple is able identifying feature is to find most often planted as a land maple keys persisting on the tree. scaped tree and must be exam ined closely. Norway maple has

Fig. 22. Mature bark of A) green/red ash, B) white ash, C) black ash, and D) blue ash.

Fig. 23. A) Twig with buds of sugar maple, B) leaf scar on sugar ma ple, C) green/red ash buds and leaf scar, D) white ash buds and notched leaf scar, E) leaf scar and hairy twig of black ash, and F) square twig of blue ash.

Manitoba maple has grey buds on butternut, hickories (Carya spp.), slender twigs that look relatively cottonwood/poplar (Populus spp.), large. The twigs are purple and and tulip-tree (Liriodendron tulipif- are coated with a white waxy pow era) appear ash-like but all have der that can be rubbed off. Mani alternately oriented branches and toba maple has a crooked form. It buds like white elm (Fig. 21C). is most easily identified when it The tulip-tree may still have its retains its clusters of maple keys. seed cones in the winter, and From a distance, with their stout there is white dotting on the bark. branches and form, black walnut,

Some tree species, such as ash, forms a bud at its base. Other have compound leaves (Fig. 24), trees such as maple, oak that is two or more leaflets on a (Quercus spp.), elm (Ulmus spp.), single leaf stalk and each leaf poplar and beech (Fagus spp.)

Fig. 24. Compound leaves of A) green/red ash, B) white ash, C) black ash, and D) blue ash.

have simple leaves (Fig. 25). If it corktree has spongy-textured does not have a compound leaf, it bark. Elder is a shrub-sized plant is not an ash. with hollow, easily breakable stems. The fruits are flat clusters Ash leaves (Fig. 24) usually have of small berries turning from green 5 - 9 finely-toothed leaflets to red or nearly black, depending (occasionally 11) of roughly equal on the species. size with the lowest (basal) two leaflets being slightly smaller than The following trees have an alter the other leaflets. Ash seeds are nating leaf and bud arrangement attached to a wing called sama (Fig. 21C) as their main difference ras, which droop towards the from ash (Fig. 23). Walnut and ground and turn from green to butternut have more than nine brown throughout the summer. leaflets. Nuts develop inside of a large green husk on these trees. Manitoba maple is the only native Leaves have a distinct citrus smell maple with a compound leaf. when crushed. Hickory leaves Manitoba maple generally has 3-5 have a shiny upper surface and leaflets (occasionally 7) with slight are aromatic when crushed. The lobes, crooked form, and clusters terminal leaflet is much larger than of maple keys. Amur corktree is the basal leaves. Honey locust an uncommon tree species. Fruits (Gleditsia triacanthos) and black are grape-like clusters of berries locust (Robinia pseudoacacia) turning green to purple. Amur have more than nine small leaflets of equal size. These are legumi nous trees that develop seed pods. Mountain-ash, which are in the rose family, are not true ashes. Leaves of these species have distinct teeth. Showy white flowers on these trees develop into clusters of bright orange ber ries. The introduced ornamental, tree-of-heaven (Ailanthus altis- sima) has many more than nine leaflets.

6.2 A KEY TO DISTINGUISH ASH FROM OTHER TREES

These simple keys will help you separate ash trees from other trees that have a similar appear Fig. 25. The simple leaf of white ance. elm.

Trees can be identified in the the leaf have many leaf summer using the leaves lets (Compound Leaf – (Summer Key) or in the winter Fig. 24) attached to a using the twigs and bark (Winter single leaf stem? Key). It is more difficult to distin guish between tree species in the If the leaf is simple, then winter, so it takes some practice the tree is not an ash to become proficient. Twigs are tree. used to identify trees without leaves. Make sure the twig exam If the leaf is compound, ined does not have missing buds go to Step 3. and is alive. We strongly advise that you examine at least two or Step 3: Does the leaf have 3 to three samples at each step of the 5 (rarely more) leaflets key to be sure the decision is cor that are irregular in rect and to familiarize you with the shape and with coarse variation that occurs within and teeth? among trees. Do not use the leaves and twigs from epicormic If yes, it is a Manitoba branches. maple (boxelder).

Summer Key If not, go to Step 4.

Step 1: Look at a branch in a Step 4: Does the leaf have 5 to tree where the branches 9 (usually 7) leaflets ar are easy to see. Are the ranged like the fingers in branches directly oppo a hand (palmate), with site (across from each the leaflets bigger above other) (Fig. 21A), or are the middle and ending the branches alternate with a small point? (staggered and not di rectly across from each If yes, it is a horsechest other) (Fig. 21C)? nut or a buckeye.

If the branches are alter If not, go to Step 5. nate, it is not an ash tree. Step 5: Are the leaves covered with translucent dots If the branches are op (glands)? Are they fra posite, go to Step 2. grant, and do the twigs have prominent lenti Step 2: Is the leaf a single blade cels? (Simple Leaf – Fig. 25) joined by its stem to a If yes, it is likely an Amur woody branch, or does corktree, which is com

monly planted in urban shield-shaped leaf areas and looks a lot like scars? ash. If yes, it is likely a If not, go to Step 6. horsechestnut or a buck eye. Step 6: Does the leaf have 5 to 11 leaflets all about the If not, go to Step 3. same size (the terminal leaflet can sometimes Step 3: Are the twigs slender, be slightly larger) and is with three distinct vein the edge (margin) of (bundle) scars inside the each leaflet smooth or crescent-shaped leaf with small teeth (Fig. scar (Fig. 23B)? 24)? If yes, it is likely a ma If yes, it is likely an ash ple. tree. Go to Sections 6.3 & 6.4 to distinguish the If not, and the leaf scar different species of ash. has many (5 or more) small vein scars (Fig. Winter Key 23C-E), it is likely an ash tree. Go to Section 6.3 & Step 1: Look at a branch in a 6.4 to distinguish the tree where the branches different species of ash. are easy to see. Are the branches directly oppo 6.3 IDENTIFYING ASH SPECIES site (across from each other) (Fig. 21A & B), or There are five native species are the branches alter (green/red, white, black, blue and nate (staggered and not pumpkin ash) of ash in eastern directly across from Canada and several more species each other) (Fig. 21C)? that are introduced and planted as landscape ornamentals. What is If the branches are alter known as red ash (Fraxinus penn- nate, it is not an ash sylvanica) in Canada, is called tree. green ash in the United States. To make matters somewhat more If the branches are op confusing, in Canada, there are posite, go to Step 2. two varieties of red ash, the north ern red ash (Fraxinus pennsyl- Step 2: Are the twigs very stout vanica var. austini) and the green with very large and ash (Fraxinus pennsylvanica var. sometimes sticky termi subintegerrima). Green ash has nal buds with large become the predominant common

name in Canada in association Bark: Mature trees have an ir with the emerald ash borer. regular diamond-shaped bark pat Pumpkin ash is extremely rare tern (Fig. 22A). The bark on twigs and occurs in a few locations in often has a reddish tinge to it. southeastern Ontario near Lake Erie. Similarly, blue ash is also a 6.3.2 WHITE ASH (FRAXINUS AMERI- rare tree but can easily be distin CANA) guished from the other ash trees by its four sided twigs. In urban Key Features: The buds are set areas, European ash and its into the leaf scar (Fig. 23D). This golden twig cultivar, and some is the only ash that may turn pur times Manchurian ash and its hy ple in the fall. Twigs are stouter brids can also be encountered. than those on green/red ash and exhibit a purple-grey colour. The The description for individual spe growth habit is neat and upright cies contains the characteristics of giving the terminal leaders the that species that allows for spe shape of a trident. cific identification. Bud: The lateral buds are all set into a notch in the leaf scar (Fig. 6.3.1 GREEN/RED ASH (FRAXINUS 23D). Leaf scars are raised giving PENNSYLVANICA) the twig a knobby appearance. Leaf: Leaves (Fig. 24B) have 5-9 Key Features: In the spring and hairless leaflets (most often 7). summer, twigs (Fig. 23C), buds The leaflets are mostly smooth- and leaves on red ash (green ash edged, often with rounded serra is the hairless variety of red ash) tions. The leaves are dark green are very pubescent, but in the fall, above, but much paler on the un they are only slightly fuzzy. Twigs der side. The leaflets are attached are less stout than in white ash to the leaf stalk by a petiole that is (Fig. 23D). The outer bark slightly longer than those in F. (epidermis) does not flake or peel pennsylvanica. on older twigs like those on white Seed: The wing of the samara ash. covers only the tip of the seed. Bud: The pubescent buds are The seed cavity is relatively raised on the leaf scar (Fig. 23C). plump. Leaf: Leaves (Fig. 24A) have 5-9 Bark: The bark has a distinct dia leaflets (most often 7) that are mond-shaped pattern on mature serrated (toothed) beyond the specimens (Fig. 22B). middle of the leaflet. Leaflets are attached to the leaf stalk by a 6.3.3 BLACK ASH (FRAXINUS NI- short petiole. GRA) Seed: The wing of the samara covers about half of the seed. The Key Features: This is the only seed cavity is relatively thin and native ash that has its uppermost narrow. lateral buds spaced distinctly be

low the terminal bud so that one broad, covering the whole, rela can see bark between the two. tively flat seed. The samara is The terminal twigs are stout. The twisted in appearance and has a species is rarely found on upland notched tip. sites. Bark: The bark (Fig. 22D) is dis Bud: The very dark brown buds tinctly grey and scaly. are raised above the leaf scar (Fig. 23E). 6.3.5 PUMPKIN ASH (FRAXINUS Leaf: Of the 7-11 leaflets, only the PROFUNDA) terminal leaflet has a petiole, the rest are sessile (attached directly Key Features: This species has to the leaf stalk) (Fig. 24C). many similar features as white Leaves are serrated along the and red ash, but much larger fea margins. tures than any other native Frax- Seed: The wing of the samara is inus spp. On more mature speci wider than those on white or mens the base will be buttressed green/red ash, covering nearly all and swollen to look like a pump of the seed. The wing is notched kin. The species is rare in Ontario at the end. and is only found in moist bottom- Bark: The bark (Fig. 22C) is corky lands. and when cut into is tight to the Bud: The buds are very pubes sapwood. cent and set into the leaf scar. Leaf: The leaves are very long 6.3.4 BLUE ASH (FRAXINUS QUAD- with 7-9 leaflets each one being RANGULATA) 10-25 cm long (other Fraxinus spp.: 7-15 cm). The petiolules are Key Features: This is the only relatively long (1 cm). Leaflets ash species with 4-sided (square) have rounded serrations and are twigs (Fig. 23F). The bark on a pubescent underneath, with the mature tree is scaly as opposed to midrib being densely hairy. the diamond-shaped bark of other Seed: The wing of the samara is Fraxinus spp. This is a medium- very broad and much longer than sized tree found on upland sites. other Fraxinus spp. (5-8 cm) and The tree is often planted as an covers most and in some cases, ornamental due to its rarity in On all of the seed cavity. tario. Bud: The lateral buds are set 6.3.6 EXOTIC ASHES above the leaf scar, which has the shape of a narrow crescent. Many species of ash in eastern Leaf: The 5-11 leaflets (most of Canada have been planted out ten 9) are coarsely serrated with side of their native range. The two asymmetrical bases (Fig. 24D). most common species are Man The leaflets are attached to the churian and European ash. The leaf stalk by a short petiole. following is a list of some of the Seed: The wing of the samara is more common species of exotic

ashes that may be encountered F. chinensis (Chinese Ash) during surveys with brief descrip tions of their diagnostic character Key Features: The eight egg- istics. shaped leaflets are downy be neath. F. excelsior (European Ash) F. latifolia (Oregon Ash) Key Features: The buds of this species are jet black. Twigs and Key Features: This species is upper branches may be yellow on found in British Colombia. The some cultivars and the bark is of twigs and buds are pubescent. ten smooth, lacking the deep fis The tips of the leaflets are sures of native species. pointed.

F. mandshurica (Manchurian 6.4 A KEY TO DISTINGUISH ASH Ash) SPECIES

Key Features: The 11 lance- This simple key will help you shaped leaflets have sunken separate the five native species of veins, are coarsely toothed, and ash and a common introduced are hairy on both the upper and ornamental (European ash) found lower surfaces. Several Manchu- in Eastern Canada. rian-black ash hybrids have been planted in Canada for their fall Summer Key foliage. Step 1: Does the leaf have F. ornus (Flowering Ash) smooth margins or a few rounded teeth along the Key Features: This species has edges (margin)? showy fragrant white flowers. If yes, and the twigs are F. angustifolia (Narrow-leafed hairless and stout (Fig. Ash) 23D) and the leaflets (5 Key Features: The three buds are 9) are hairless below arranged in a whorled fashion on (except along the veins), the twig. the tree is a White Ash (Fraxinus americana). F. bungeana (Bunge’s Ash) The seed wing is ta pered and surrounds Key Features: Leaves and flow only the tip of the seed ers are downy when first emerg case. ing. This species is a small tree or shrub. If yes, and the twigs are hairy and stout and the leaflets are hairy, large,

thick and with 1 cm long the leaflets attached by stems, it is a pumpkin a small stem (petiole) to ash (Fraxinus pro- the central leaf stalk funda). The seed wing (Fig. 23A & C)? is widest at or above the middle. If yes, and the twig has four prominent corky If not, go to Step 2. ridges, giving it a four- sided appearance (Fig. Step 2: Does the leaf have 23F), and the leaflets toothed margins and are are asymmetrical at the the leaflets directly at base, the tree is a blue tached (without a stem) ash (Fraxinus quad- to the central leaf stalk rangulata). The seed (Fig. 24C)? wing is broad and twisted and surrounds If yes, and there are 7 the flat seedcase. 11 leaflets with dense tufts of reddish-brown If yes, and the twig lacks hair near where the leaf ridges and is round in let attaches to the cen- cross section and the tral leaf stalk (Fig. 24C), leaflets are symmetrical the tree is a Black Ash at the base (Fig. 24A), (Fraxinus nigra). The the tree is the green/red seed wing is often ash (Fraxinus pennsyl- twisted and surrounds vanica). The seed wing the seed case and is flat, sometimes with a sometimes has a small small notch at the tip notch at the tip. and surrounds about one-half of the seed If yes, and there 9-15 case and stays on the leaflets that do not have tree almost all winter. tufts of hair where the leaflet attaches to the Winter Key central leaf stalk, the tree is an European ash Step 1: Does the twig have four (Fraxinus excelsior). prominent corky ridges The seed wing is wide, giving it a four-sided flat and surrounds the appearance (Fig. 23F)? seedcase. If yes, the tree is a blue If not, go to Step 3. ash (Fraxinus quad- rangulata). Step 3: Does the leaf have toothed margins and are If not, go to Step 2.

Step 2: Are the twigs round? Step 5: Is the tree in a very wet site with a swollen trunk If yes, and the buds are (looks like a pumpkin) at noticeably deep inky the base, and are the black in colour, the tree twigs densely hairy? is an European ash (Fraxinus excelsior). If yes, the tree is a pumpkin ash (Fraxinus If yes, but the buds are profunda). reddish to dark brown, go to Step 3. If not, the tree will be green/r ed ash Step 3: Are the terminal buds (Fraxinus pennsyl- conical and dark brown vanica). The leaf scar to black, and is there underneath the bud will bark clearly visible be have a straight edge at tween the terminal buds the top and will look like and the first pair of lat the letter D when turned eral buds just below? on its side (Fig. 23C). The twigs will be hairy to If yes, and the twig is smooth or nearly so and smooth with corky pur tend to be somewhat plish lenticels, the tree is flattened. a black ash (Fraxinus nigra). 7. EXAMINATION METHODS

If not, go to Step 4. Visual surveys can be conducted year round but slightly different Step 4: Do the leaf scars under methods are used in different sea neath the buds have sons. The best time of year to see deeply U– or V–shaped all or most of the symptoms is dur notches and are the lat ing late summer and fall. eral buds set close up against the terminal From late July until leaf-drop in buds leaving no visible the fall is when the trees begin to bark between (Fig. show signs of stress due to the 23D)? heaviest larval feeding activity. Epicormic shoots and thinning If yes, and the twig is crowns start to become very evi smooth, the tree is a dent during this period. This time white ash (Fraxinus period is best for observing all of americana). the EAB signs and symptoms. Bark deformities are easiest to If not, go to Step 5. observe when the leaves are off the trees (October/November to