Identifying the leaves of trees native to northwest Iowa | Dickinson County Conservation Board
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Identifying the leaves of trees native to northwest Iowa

October 18, 2017
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Fall is the time of year to look at leaves. We pick them up and marvel at colors. We rake them up in the yard. We jump in the piles and toss them in the air.

But what kind of leaf are you looking at?

We have put together a list of different kinds of leaves from trees native to northwest Iowa so you can know what you’re looking at when enjoying foliage this fall.

(Read about the fuzzy stuff found on oak leaves.)

But first, some background as to how leaves are described.

Leaf composition

A leaf has two parts, the blade which is the large flat portion and the narrow stalk.

Graphic of leaf composition

Simple: Single blade and stalk, what we would consider a normal leaf such as on a maple or oak tree.

Compound: Leaflets are arranged along two sides of a central axis.

Once-pinnately compound: The leaflets come out directly from the stalk, across from each other.

Twice-pinnately compound: Leaflets come off of a stalk that comes off of the main stalk attached to the branch.

Palmately compound: Leaflets radiate from a single point, like fingers from a hand.

Leaf arrangement

The spot where leaves are arranged on a twig is the node.

Alternate: One leaf per node.

Opposite: Two leaves at each node, on opposite sides of the twig.

Leaf shape

Leaves come in eight typical shapes, and each shape could have smooth or toothed edges.

Graphic of leaf shapes

Now, on to what leaves you might be seeing this fall.

(Read about the Horseshoe Bend oak savanna restoration project here.)

Boxelder (Acer negundo)

Photo of boxelder leaf

Photo by Chrumps, via Wikimedia Commons

Leaves are once-pinnately compound, directly opposite of each other. There are usually three or five leaflets, although they range from three to nine in number. Boxelder leaves are 2-4 inches long, with coarse edges and sometimes shallow lobes.

Green Ash (Fraxinus pennsylvanica)

Photo of green ash leavesLeaves are once-pinnately compound, opposite of each other. There are five to nine leaflets that are 2-6 inches long and usually oblong-lanceolate in shape. The leaf edges are toothed. The leaf surface is glossy and hairless.

Black Walnut (Juglans nigra)

Photo of black walnut leaf and nut

Leaves are once-pinnately compound, alternate each other instead of opposite each other on stalks 1-2 feet long with 11-23 leaflets. They are ovate-lanceolate-shaped, 2-4 inches long and finely toothed. The surface of each leaf is hairless but the bottom is hairy.

Silver Maple (Acer saccharinum)

Photo of a silver maple leaf

Photo by Dimitir Naydenov, via Wikimedia Commons

Silver maple leaves are simple, with each leaf growing on its own stalk opposite another. They have five deep lobes, and those lobes have toothed edges. The underside of each leaf is very pale or whitened.

Bur Oak (Quercus macrocarpa)

Photo of a bur oak leaf

Leaves are simple and alternate along the twig. The obovate-shaped leaves are shallowly lobed above the middle with deep lobes near or below the middle. Each leaf is 6-10 inches long and is paler and finely hair on the undersurface.

Red Oak (Quercus rubra)

Photo of a red oak leaf

Photo by Crusier, via Wikimedia Commons

Leaves are simple, growing individually in an alternating pattern on either side of the twig. Each leaf has seven-11 lobes with bristled tips. The lower surface of the leaf is slightly paler than the top.

Northern Pin Oak (Quercus ellipsoidalis)

Photo of a northern pin oak leaf

Photo by David J. Stang, via Wikimedia Commons

The northern pin oak is native to the northern part of Iowa, although it’s not common in northwest Iowa. It has simple leaf that alternate along the twig, and each leaf has five-seven lobes. The edges are smooth, but each tip has little bristles, often broader at the tip than the base.

Downy Hawthorn (Crataegus mollis)

Photo of a hawthorn leaf

Photo by Magnus Manske, via Wikimedia Commons

Also called the red haw, this tree has simple leaves coming alternately off the twig. They are ovate in shape and shallowly lobed, 2.5-4 inches long. Each leaf is toothed and is often hairy underneath.

Prairie Crabapple (Malus ioensis)

Photo of a crabapple leaf

Photo from www.illinoiswildflowers.info

Although more known for its flowers and fruit, the prairie crabapple also has interesting leaves that are simple, alternate and oblong-ovate. The leaves are shallowly lobed, 2.25-4 inches, toothed and hairy on the undersurface.

Eastern Cottonwood (Populus deltoides)

Photo of cottonwood leaf

Photo by Dave Powell, USDA Forest Service, via Wikimedia Commons

Leaves are shaped like a rounded triangle, are simple and are located alternately along the branch. Each leaf is 3-6 inches, smooth and has a toothed edge.

American Elm (Ulmus americana)

Photo of an american elm leaf

Leaves are simple, alternate, elliptic and have an uneven base. The edges are doubly-toothed, and veins run directly into the teeth.

Slippery Elm (Ulmus rubra)

Photo of a slippery elm leaf

Like the American elm, leaves are simple, alternate, elliptic and have slightly uneven bases. The lower surface is paler and hairy.

Black Willow (Salix nigra)

Photo of a black willow leaf

Photo from www.illinoiswildflowers.info

Black willow leaves are unique — simple, alternate and narrowly lanceolate, tapering to slender tips. Each leaf is 3-6 inches and finely toothed on the edges, with almost 18-25 tooths per inch.

Peachleaf Willow (Salix amygdaloides)

Photo of a peachleaf willow

Photo from www.illinoiswildflowers.info

This tree is native throughout the state and has leaves that are simple, alternate, lanceolate and tapered to an almost tail-like end. The edge is finely toothed, and the undersurface is a pale bluish-green.

Sandbar Willow (Salix interior)

Photo of a sandbar willow leaf

Photo from www.illinoiswildflowers.info

This small tree or shrub has simple, alternate and linear-lanceolate leaves with tapered tips.

Ironwood or Hop Hornbeam (Ostrya virginiana)

Photo of an ironwood leaf

Photo by Steven Katovich, USDA Forest Service, via Wikimedia Commons

Leaves are simple, alternate, oblong-ovate and sharply toothed.

Hackberry (Celtis occidentalis)

Photo of a hackberry leaf

Photo by Sapphosyne, via Wikimedia Commons

Leaves are simple, alternate, ovate and 2.5-4 inches ong. Margins are toothed, and the largest three veins meet at a single point in the base.

Black Cherry (Prunus serotina)

Photo of a black cherry leaf

Photo by Pleple2000, via Wikimedia Commons

Leaves are simple, alternate, oblong-lanceolate, 2-6 inches long, with finely toothed edges. The edges of the teeth curve inward.

Chokecherry (Prunus virginiana)

Photo of chokecherry flowers

Photo by Kurt Stuber, via Wikimedia Commons

This small tree/shrub has simple leaves, alternate, oval or obovate. Each is 2-4 inches long with fine teeth that point outward.

American Plum (Prunus americana)

Photo of an american plum leaf

Photo by Аимаина хикари, via Wikimedia Commons

This native has simple, alternate and oval to oblong-oval leaves that are 2-4 inches long. A good way to tell it apart from cherries is that it has often thorny twigs.

American Basswood (Tilia americana)

Photo of an american basswood leaf

The base of the leaf is heart-shaped and often unequal. The surface is smooth except for small tufts of hairs in the vein axils beneath. Leaves are simple, alternate and nearly round with toothed edges.

 

 

 

 

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