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The Monday Garden
Great Americans: Ashes & Elders

Issue No. 138 - November 14, 2004
by Sue Sweeney

  
To many humans, box elders and ashes are respectively trash and treasure. Nine out of 10 squirrels, however, disagree about the box elder.

The box elder (Acer negundo), a native maple, is considered a “trash tree” in that it’s a hardy, weedy tree that grows fast and dies fast, dropping limbs all over in storms. The wood’s soft and is rumored to be used for (you guessed it) boxes. Alternatively, the name is said to come from the resemblance of the lumber to that of boxwoods. The box elder is good for windbreaks and naturally ranges from Zone 2 in southern Saskatchewan, west to Texas, and south to Zone 9 in parts of Mexico. It has become an invader in Europe.

Our premiere native ash, the white ash (Fraxinus Americana), in contrast, is a gloriously slow-growing, tall hardwood tree. It “plays well with others”, and makes light shade so it is easy on the lawn, even if this ash is also a prolific maker of seedlings. The white ash is the source of the prized light, strong, flexible wood used to make that Great American icon the baseball bat, among other things Americana such as hoe handles, arrows, oars, snow shoes and tennis rackets. Ashes are native to all Northern temperate zones; North American has about 16 species.

 

pictures: a young box elder at Cove Island in Stamford CT and an young ash along the Mill River in Stamford CT, both 2003.

 
When it comes to trees, sometimes humans have a hard time knowing trash from treasure. (Squirrels do not have this problem—they always know a good thing when they see it). Depressingly for us, the box elder is called the “ash-leafed maple” because it so closely resembles the native ashes. Both the ashes and the box elders have opposite buds and compound leaves. To make identification even more difficult, the ashes also have winged seeds (“samaras”) like the maples.

If you want to be as savvy as a squirrel in differentiating trees, a little botany-speak is useful. As botanists view the world, plant leaves generally come in either “simple” or “compound”.

• “Simple” means a single, undivided leaf attached directly to a twig (example: oak).
• “Compound” means the leaf is divided into leaflets which are attached to a leaf stalk that is then attached to a twig.

You can tell the difference between leaf stalks and twigs because:

Leaf stalks fall with the leaves in autumn while twigs are permanent and mature into branches.
Twigs have next year’s buds snuggled in the leaf axils; leaf stalks don’t—look for the bud at the base of the stalk.

If background helps: compound leaves probably evolved from simple leaves as a way to expand leaf surface without adding weight. The leaf stalk was probably once the central leaf vein and the leaflets were leaf lobes. The divisions between the lobes grew deeper and deeper to cut the overall weight of the leaf until the lobes became full separated into leaflets.

In botany-speak, plant parts such as buds, leaves, veins, etc., are generally arranged in “opposite”, “alternate”, or “whorled” patterns.

• “Alternate” means the buds alternate along the shoot;
• “opposite” means the buds are in pairs across from each other on the shoot;
• “whorled” means the plant has several buds at approximately the same level on the shoot, radiating out in different directions.

 
Picture 1: the American beech has alternating, simple leaves (note the brown buds in the leaf axils). In picture 2, the sumac has compound leaves with leaflets which are opposite each other on the leaf stalk but in picture 3 you can see that the sumac leaves stalks are alternate on the branch.
 
Our ashes have compound leaves. The native box elder is believed to be the one maple in the whole world with compound leaves.

Numerous other North American native and naturalized trees also have compound leaves – ailanthus, locust, pecan, walnut, hickory, and sumac come to mind immediately.

However, once you know the difference between opposite and alternate, you can quickly distinguish the elders and ashes from the rest of the compound-leafed trees by checking the bud and branch arrangement. Most North American trees are alternate. The major North American trees that have opposing buds are the maples and the ashes. (Ashes are olive family members like the imported lilac, privet, and forsythia). The dogwood (cornus) family also generally has opposing buds.

 
Pictures: examples of the opposite branching of the box elder
 

Pictures: examples of the opposite branching of local ashes; note the upward curve of the branches.

 
Now, telling the box elders and ashes from each other, well, that’s bit trickery.

LEAF: The box elder has 3 or 5 leaflets (some times 7 or 9) and the leaves may be coarsely toothed. The ashes have more leaflets – usually 7 (sometimes 5 or 9); the ashes leaves are oval with pointed ends and a finely toothed edge. The box elder leaves are often light colored, particularly in spring. In fall, the box elder turns a non-showy yellow (occasionally red); the ashes are gorgeous in yellows, reds, and purples. The box elder leaflets may have long stems; the ash leaflets are short stemmed or stemless.

 
picture: the compound leaves of box elder, with and without lobes, coarse teeth, and long leaflet stems.
 
SEED: Both have tan winged seeds (samaras) hanging in clusters throughout the summer and fall. The box elder samaras come in pairs; the ash samaras are singles. The box elder samaras have sweeping curves; the ash samaras (called “keys”) are straight, like boat paddles.
 
pictures 1 and 2: box elder samaras ; picture 3: ash samaras
 
FLOWER: The box elder has characteristic maple family flowers – very pretty and showy. The ash flowers are less conspicuous.
 
Pictures: box elder twig and flower, Cove Island, Stamford CT, spring 2004; ash twig Strawberry Hill Ave Stamford CT Nov 2004
 
TWIG: The box elder twigs are colorful – usually bright green, sometimes pale red or purple. The stout ahs twigs are a neutral shade (often gray-olive)

BARK: The bark of a mature ash has deep furrows with flat tops like corduroy and the furrows make a diamond patterns along the trunk. Depending of the species, ash bark tends to be very dark. Box elder bark is lighter colored and much smoother with shallow furrows.

FORM: Box elders tend to be short and round in outline with low branches; ashes are tall and stately with high branches.

 
pictures: trunk of an ash at Scalzi Park, Stamford CT 2003; fallen box elder trunk, Cove Island, 2004.
Note that the mature scaffold branches are no long in opposing pairs- one side or the other has been pruned or died off.
 
Distinguishing the ashes from each other is even trickery than telling a box elder from an ash. One major way is by location: the majestic white ashes prefer upland, moist but well-drained locations; many of the other native ashes prefer swampy bottomland. The white ashes are the biggest ones and their leaves are lighter on the undersides. Leaf and samara shape also differ, as does bark color and texture. However, ashes, like maples, interbreed, so telling the ashes apart can be very difficult. For starters, congratulate yourself for being able to recognize the ash family.

Now for the squirrel’s POV (“point-of-view”): Squirrels value both the ash and the box elder for the yummy seeds and buds. Both trees provide good habitat for squirrels and many birds. In addition, the box elder has the characteristic sugary sap of the maple family which squirrels enjoy almost as much as humans do. Many birds also eat the seeds of both trees. For unknown reasons (at least to me), tiger swallowtail butterflies are reported to be attracted to the ash samaras.

 
Picture: squirrel lurking in a blooming box elder. Cove Island, Stamford, CT, Spring 2004.
  
From The Monday Garden. Copyright © by Sue Sweeney. Reproduced with permission. 

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