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Austrian Pine

Although not native to Iowa, the Austrian pine (Pinus nigra), also called European black pine, has been planted quite widely in the state and especially in the western one-third where it has been planted both in farmstead windbreaks and as an ornamental. Due to many disease problems this species is no longer recommended in Iowa.

Hardiness: Zones 3b through 7 - Survives in zone 8, though rarely seen. Grows best in colder climates.

Austrian pine tree
Austrian Pine Tree

Growth Rate: Medium (grows 35 to 50 feet after 20-30 years)

Mature Shape: Densely pyramidal when young. Becomes a large, flat-topped tree with a rough, short trunk and low, stout, spreading branches.

Height: 50 to 60 feet tall (some have been seen at 
100 feet tall)

Width: 20 to 40 foot spread

Site Requirements: A very hardy tree that can survive city conditions better than most pines, but also enjoys the seaside environment and tolerates sandy soils well, too. Very tolerant of soils, if moist, but can stand some dryness and exposure. Resists heat and drought. Can succeed in fairly heavy clay.

LeavesStiff, sharp needles that occur in bundles of two

Flowering Dates: May - June

Seed Dispersal Dates: October - November

Seed Bearing Age: 15-40 Years

Seed Bearing Frequency: Every 2-5 years

The tree grows moderately fast, 75 to 100 feet tall when mature, and is hardy and is quite drought resistant. When grown in the open, it holds its branches quite close to the ground. The needlelike leaves occur in bundles of two, are 4 to 6 inches long, are stiff and sharp pointed, and of a light green color. The egg-shaped cones are 2 to 3 inches long and 1 to 1-1/4 inches wide. The cones open during the late fall and early winter.

Side by side view of young Austrian pine fruit and mature cone
Austrian Pine Fruit - Photos by Paul Wray, Iowa State University

Diseases that Can Affect Austrian Pine

Insects that Can Affect Austrian Pine

 

Austrian pine flower cluster
Austrian Pine Flowers - Photo by Paul Wray, Iowa State University

Austrian pine twigs
Austrian Pine Twigs - Photo by Paul Wray, Iowa State University

Austrian pine needles
Austrian Pine Leaves, Photo by Paul Wray, Iowa State University

 

 

Black Locust

Not native to Iowa, the black locust (Robinia pseudoacacia) is included here because it has been planted so widely over the state, has escaped from cultivation and is sometimes found growing in mixture with native species. Its natural range extends from Pennsylvania southwest ward to Alabama and west ward to southern Illinois. It has been planted widely in Iowa for post production and erosion control. The tree often suffers extensive damage from the locust borer insect.

two examples of black locust leaves
Black Locust Leaves - Photos by Paul Wray, Iowa State University

Hardiness: Zones 4 through 8

Growth Rate: Aggressive; Rapid

Mature Shape: Upright to spreading ovular shape

Height: 50 feet

Width: 25 feet

Site Requirements: Prefers rich, deep, moist, well-drained, and full to partial sun. However, commonly found in poor soil conditions, especially thin and near limestone outcrops.

Leaves: Alternate, compound, with thorns or spines

Flowering Dates: May - June

Seed Dispersal Dates: September - April

Seed Bearing Age: 10 years

Seed Bearing Frequency: Yearly or bi-yearly

Seed Stratification: Soak seeds in warm water for 24 hours.

The leaves are pinnately compound with 11 to 15 leaflets 1 to1-1/2 inches long, rounded at both ends and with smooth margins. The twigs are crooked and angular with short, stout, single, unbranched thorns, one-half inch long. The fruit is a dark, red-brown, flexible pod 3 to 4 inches long, containing small, reddish brown bean-like seeds. On young branches the bark is smooth and greenish to brown in color. On older branches and trunks it is broken into a network of coarse, deep ridges and is gray to gray-brown in color.

black locust bark
Black Locust Bark, Photo by Paul Wray, Iowa State University

black locust twig
Black Locust Twig, Photo by Paul Wray, Iowa State University

black locust thorn
Black Locust Thorn - Photo by Bill Cook, Michigan State University, Bugwood.org

side by side photos of dried black locust fruit with an open pod showing seeds and non-dried black locust fruit
Black Locust Fruit - Photos by Paul Wray, Iowa State University

side by side photos of black locust flowers, one white and one purple/pink
Black Locust Flowers - Photos by Paul Wray, Iowa State University

Black Spruce

The black spruce (Picea mariana) is not native to Iowa. It occurs in the northeastern United States, and Minnesota, Wisconsin, and Michigan; from the northern range of North America to Alaska, Yukon, and British Columbia eastward to Nova Scotia, Newfoundland, New Brunswick, and Quebec and extending north all the way to the very limit of tree growth.

black spruce trees
Black Spruce Trees - Photo by Keith Kanoti, Maine Forest Service, Bugwood.org

Hardiness: Zones 1 though 6

Growth Rate: Slow

Mature Shape: Narrow pointed crown; straight trunk with little tapper; short, compact, and drooping branches

Height: 40-50 feet

Width: 15-30 feet

Site Requirements: Thrive in partial to full sun with neutral or acidic soil; can tolerate poorly drained soil.

Flowering Dates: May - June

Seed Dispersal Dates: Retains cones in a semi-serotinous state

Seed Bearing Age: 10 years, but generally not in large quantities until 30 years

Seed Bearing Frequency: Yearly, with bumper crops every four years

Seed Stratification: Warm stratification for 16 days at 68°F to 85°F

Grows in muskegs, bogs, barren and stony slopes, but makes its best living in well-drained bottomlands. It is also often referred to as “swamp spruce” or “bog spruce.”

The leaves are needle-like, bluish-green in color, blunt-pointed, ¼ to 3/8 inch in length, and with a whitish bloom when young. The cones are short and ovoid, and measure from ¾ to 1 inch in length. The bark is grayish-brown with thin scales. It is believed that red and black spruces hybridize, and some authorities consider the red and black spruces to be variations of a single species – there is also speculation that black spruce hybridizes with white spruce, but not verified.

It is primarily used for paper pulp and Christmas trees, and secondarily for spruce beer and spruce gum in the northern regions.

flaky grayish black spruce bark
Black Spruce Bark - Photo by Keith Kanoti, Maine Forest Service, Bugwood.org

black spruce cones
Black Spruce Fruit - Photo by Keith Kanoti, Maine Forest Service, Bugwood.org

black spruce needles
Black Spruce Needles - Photo by Keith Kanoti, Maine Forest Service, Bugwood.org

Catalpa

The catalpa (Catalpa speciosa) is not native to Iowa. It was introduced as an ornamental tree because of its large, showy flowers. After the flowers bloom, long, cylindrical pods filled with small winged seeds form. This distinctive fruit hangs on the trees all winter.

catalpa tree in winter with no leaves
Catalpa Tree - Photo by Paul Wray, Iowa State University

Hardiness: Zones 4 through 9

Growth Rate: Medium to Fast. 15' over 7 to 8 year period.

Mature Shape: Tree with narrow, open, irregular, oval crown.

Height: 40-60 feet 

Width: 20-40 feet

Site Requirements: Very tolerant of different soil conditions. Prefers deep, moist, fertile soil, but can withstand extremely hot, dry environments.

Leaves: Opposite (whorled) simple

Flowering Dates: May - June

Seed Dispersal Dates: Late Winter - Spring

Seed Bearing Age: 20 years

Seed Bearing Frequency: Every 2-3 years

Seed Stratification: Seeds disperse in the spring and immediately germinate. No stratification period is needed.

The leaves are 8 to 12 inches long and heart-shaped. Leaves are thick and firm, dark green above and downy beneath. The fruit is a slender, 8 to 20 inch long pod that ripens in early autumn. The pod hangs on the tree all winter and opens in the spring before falling off.

grouping of white catalpa flowers and close up of single flower showing dark central stripes and yellow orange central spots
Catalpa Flowers - Photo by Paul Wray, Iowa State University

Catalpas grow rapidly. The trunks are short, often crooked, supporting a broad, rounded crown of slender, spreading branches and thick twigs.  The bark is thick, reddish brown, with scaly, longitudinal ridges.

Insects that Can Affect Catalpa

 

 

catalpa twig
Catalpa Twig - Photo by Paul Wray, Iowa State University

catalpa fruit look like long dark pods
Catalpa Fruit - Photo by Paul Wray, Iowa State University

catalpa leaves
Catalpa Leaves - Photo by Paul Wray, Iowa State University

Colorado Blue Spruce

Native only to the Rocky Mountain states, the blue spruce (Picea pungens) is one of our most beautiful evergreens and has been planted widely throughout Iowa for ornamental use. It is a hardy tree with compact, dense foliage and a slow growth rate.

colorado blue spruce tree
Colorado Blue Spruce Tree - Photo by Paul Wray, Iowa State University

Hardiness: Zones 3 through 7

Growth Rate: Slow to Moderate (30-50 feet after 35-50 years)

Mature Shape: Regular narrow to broad pyramid with horizontal stiff branches to the ground. Very dense. Often becomes open, poor, and dingy in old age.

Height: 30 to 60 feet under average landscape conditions
(90 to 135 feet in the wild)

Width: 10 to 20 feet under average landscape conditions
(20 to 30 feet in the wild)

Site Requirements: The blue spruce prefer rich, moist soil in full sunlight, but are very adaptable.

Flowering Dates: April - June

Seed Dispersal Dates: Fall - Winter

Seed Bearing Age: 20 years; optimum seed production 50 to 150 years

Seed Bearing Frequency: Yields full crops of cones every 2 or 3 years. 

Seed Stratification: Warm stratification for 16 days at 68°F to 85°F

colorado blue spruce needles
Colorado Blue Spruce Leaves - Photo by Paul Wray, Iowa State University

Needles are single, very stiff and sharp pointed, angular or four-sided, 1 to 1-1/4 inches long, with a bluish color especially distinct on the new growth. Cones are light brown and cylindrical, very sharp and 2-1/2 to 4-1/2 inches long. The bark is silvery gray-brown and composed of many thin scales divided into vertical ridges. Colorado blue spruce grow 75 to 100 feet tall. They make good winter cover for wildlife.

Diseases that Can Affect Colorado Blue Spruce

Insects that Can Affect Colorado Blue Spruce

 

European Larch

Several species of larch have been planted in Iowa, mostly for farmstead protection. The larch is not a true evergreen since it is one of the few conifers which lose their leaves in winter.  It is a tall tree with a straight, central trunk and many spreading branches. It grows 40 to 80 feet tall.

european larch tree in the summer with green leaves
European Larch Tree in the Summer - Photo by Paul Wray, Iowa State University

Hardiness: Zones 2 through 6

Growth Rate: Moderate to Fast

Mature Shape: Upright, spreading, and vase-shaped canopy

Height: 70-75 feet

Width: 25-30 feet

Site Requirements: Sun and well drained soil

Flowering Dates: March - May

Seed Dispersal Dates: September - Spring

Seed Bearing Age: 10 years

Seed Bearing Frequency: Every 3-10 years

Seed Stratification: No stratification period is needed.

The leaves are needle like, but are flat, soft, slender, 3/4 to 1-1/4 inches long and borne in clusters on spur like branches. In the spring the needles are bright green and very soft and flexible. In the fall they turn a dull yellow just before falling off.

The cone is small and nearly spherical, 1/2 to 3/4 inches long. The young cones are reddish to green in color, turning brown as they mature often remaining on the tree for several years.  As they mature and open in the fall, they liberate small, winged seeds.

The twigs are light brown to gray in color, and covered with numerous tiny spurs or short branches. The rough bark separates on the surface into thin, reddish brown scales.

side by side images of white european larch flowers and a pink european larch flower
European Larch Flowers - Photos by Paul Wray, Iowa State University

european larch cone
European Larch Fruit - Photo by Paul Wray, Iowa State University

brown european larch tree in the winter with brown leaves
European Larch Tree in the Winter - Photo by Paul Wray, Iowa State University

european larch leaves
European Larch Leaves - Photo by Paul Wray, Iowa State University

Horse Chestnut

The horse chestnut (Aesculus hippocastanum) is a medium-sized to large tree, reaching a height of 50 to 70 feet.  It has a spreading, rounded crown and massive clusters of flowers. The horse chestnut provides dense shade and has been widely planted in Iowa as an ornamental.

Hardiness: Zones 4 through 7

side by side images of white and pink horse chestnut flowers and pink and white horse chestnut flowers
Horse Chestnut Flowers, Photos by Paul Wray, Iowa State University

Growth Rate: Moderate

Mature Shape: Oval

Height: 50-75 feet

Width: 40-70 feet

Site Requirements: Vary adaptable

Leaves: Opposite, compound

Flowering Dates: April - June

Seed Dispersal Dates: September - October

Seed Bearing Age:

Seed Bearing Frequency: Yearly

Seed Stratification: Prechill seeds for 4 months at 34°F to 40°F

The large leaves are palmately compound with seven individual leaflets which are broad toward the tip and somewhat narrowed near the base. The leaflets have no stalks, and at the tips they taper to an abrupt point. They are hairy when young but become smooth as they mature.

The fruit is round and covered with spines. Inside the spiny husk is a bitter, inedible nut with a large, conspicuous scar.

The twigs are reddish brown, stout and have prominent horse-shoe-shaped leaf scars with a series of so-called bundle-scars around the margin serving to represent the nails.

horse chestnut leaves
Horse Chestnut Leaves - Photo by Paul Wray, Iowa State University

horse chestnut trunk showing bark
Horse Chestnut Bark - Photo by Paul Wray, Iowa State University

horse chestnut twig
Horse Chestnut Twig - Photo by Paul Wray, Iowa State University

Jack Pine

The jack pine (Pinus banksiana) is a native of the Lake states, the northern New England states and much of Canada. It has been planted widely in Iowa, but is a less desirable tree than many of the other pines. It will survive on the driest soils in the state, and makes rapid growth during the first 10 to 15 years. It is a rather small tree, reaching a height of 40 to 60 feet under favorable conditions. Normally the tree has thin, open foliage and is not tolerant of shade. As the lower branches are shaded and die, the old cones remain on the tree for many years.

jack pine tree
Jack Pine Tree - Photo by Keith Kanoti, Maine Forest Service, Bugwood.org 

Hardiness: Zones 3 through 7

Growth Rate: Rapid 

Mature Shape: Crown becomes irregularly rounded or spreading and flattened

Height: 30-50 feet

Width: 10-18 feet

Site Requirements: Especially hardy on dry sandy soils but adaptable on most well drained soils

Flowering Dates: May - June

Seed Dispersal Dates: September

Seed Bearing Age: 3-15 years

Seed Bearing Frequency: Every 3-4 years

Seed Stratification: Prechilling for one week at 34°F to 40°F

The needles occur in bundles of two and are shorter than most other pines, 3/4 to 1-1/2 inch long, and are quite stiff and pointed and tend to spread apart from one another forming a V.

The small cones are about 1-1/2 inches long, often strongly curved, persistent and sometimes remain on the trees and contain good seeds for many years. The cone tips curve toward the branch tips. Cones are green or purplish when full-grown, turning light yellowish-brown as they ripen.

Jack pines tend to have straight trunks. Their branches are long and spreading, forming an open ragged crown. The dark brown bark is irregularly divided into small scales.

jack pine cones on a branch
Jack Pine Fruit - Photo by Paul Wray, Iowa State University

jack pine needles and flowers
Jack Pine Leaves and Flowers - Photo by Paul Wray, Iowa State University

Norway Maple

A native to Europe, the Norway maple is a medium to large size tree. It can reach heights of up to 100 feet, but is commonly seen at 40 to 60 feet, with a trunk diameter of 1 to 2 feet.

Hardiness: Maples vary in hardiness. Most fall into zones 4 through 8, but some are less tolerant of cold or heat than others. When selecting a maple tree, be sure to select a species suited for Iowa's winter.

Norway maple tree
Caption

Growth Rate: Maples vary in growth rate. Maples that are fast growing tend to have weak wood and may suffer from wind and ice damage. Slower growing maples have heavier, harder wood, making them less susceptible to branch and limb drop.

Mature Shape: Maples typically have a large, rounded crown. Tree canopies may be very dense or wide spreading.

Height: Mature height varies with species.

Width: Width varies with species.

Site Requirements: Maple trees perform best in moist, well-drained soils. Site requirements vary with the species of maple.

Flowering Dates: April - June

Seed Dispersal Dates: October - November

Seed Bearing Frequency: Each year

Seed Stratification: Prechill 2 months at 34°F to 40°F

The leaves are 5 to 7-lobed with irregular serrated margins, measuring 4 to 7 inches in both length and width, petioles are 3 to 4 inches in length. The leaves are very similar to sugar maple. However, Norway maple has one definitive characteristic; a milky sap is present when a petiole is broken. Additionally, the leaves are a darker green, turning pale yellow in autumn. The Norway maple will also hold its foliage for two weeks longer than native North American maples in autumn. The fruit is a samara; two papery wings, each about 2 inches long, and maturing in the early autumn. The Norway maple has been planted throughout North America as an urban ornamental shade tree due to its high tolerance to urban pollution.

Norway maple leaf
Norway Maple Leaf - Photo by Paul Wray, Iowa State University

Diseases that Can Affect Norway Maple

Pests that Can Affect Norway Maple

Norway maple branch showing bark
Norway Maple Bark - Photo by Paul Wray, Iowa State University

Norway maple small green flowers
Norway Maple Flowers - Photo by Paul Wray, Iowa State University

Norway maple twigs
Norway Maple Twigs - Photo by Paul Wray, Iowa State University

Norway maple fruit, red and green winged seed
Norway Maple Fruit - Photo by Bill Cook, Michigan State University, Bugwood.org

Norway maple leaf and green winged fruit
Norway Maple Leaf and Fruit - Photo by Paul Wray, Iowa State University

Ponderosa Pine

Not native to Iowa, the ponderosa pine occurs widely throughout the Rocky Mountain region. It is one of our largest pines, reaching a height of 150 or more in its native habitat. It is hardy, drought resistant and has been planted some in western Iowa for windbreaks and ornamental use.

ponderosa pine trees
Ponderosa Pine Trees - Photo by Chris Schnepf, University of Idaho, Bugwood.org

Hardiness: Zones 3 through 7

Growth Rate: Moderate

Mature Shape: Irregular

Height: 60-100 feet

Width: 25-30 feet

Site Requirements: Adapted to a wide range of sites including rocky dry alkaline and salty sites except for sites with excessive moisture or poor drainage

Flowering Dates: April - June

Seed Dispersal Dates: August - September

Seed Bearing Age: 16 to 20 years

Seed Bearing Frequency: Every 2 to 5 years

Seed Stratification: No stratification period is needed.

The 5- to 8-inch yellow-green needles are coarse and quite stiff. The needles can occur in bundles of two and threes on the same tree.

The tan-brown cone is 3 to 6 inches long and armed with stout, slender barbs, usually hooked backward. The bottom portion of the cone scales often stay attached to the limb when the cone falls.

The twigs are short, thick and often many branched. On young trees the bark is dark brown to nearly black and is broken into ridges. On older trees the bark becomes orange colored to cinnamon red.

three ponderosa pine cones
Ponderosa Pine Fruit - Photo by Paul Wray, Iowa State University

ponderosa pine needles
Ponderosa Pine Leaves - Photo by Paul Wray, Iowa State University

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