Pinus: Their Cultivation in Minnesota

PINUSTheir Cultivation in MinnesotaAlexander Q. Susko

Table of ContentsKingdom Plantae Division Pinophyta Class Pinopsida Order Pinales Family Pinaceae Subfamily Pinoideae Genus Pinus Subgenus Ducampopinus P. aristata..6 Subgenus Pinus P. banksiana8 P. contorta...10 P. densiflora12 P. mugo...14 P. nigra ...16 P. ponderosa...18 dddddP. resinosa ..20 P. rigida.. 22 P. sylvestris.24 Subgenus Strobus P. cembra.26 P. koraiensis28 P. strobus.30

Taxonomy of the Pines at the Minnesota Landscape Arboretum

Introduction...................2 Morphology...4 Species Profiles..6-30 Cultivating Pines...33 Common Diseases.35 Bibliography...38

The purpose of this book is to highlight Pinus species suitable for cultivation in Minnesota and similar climates, using trees at the Minnesota Landscape Arboretum in Chaska, MN as examples. Alexander Q. Susko. Author. Student, University of Minnesota Twin-Cities

Pinus Their Cultivation in Minnesota

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IntroductionPines are members of the genus Pinus, and areclassified as members of the family Pinaceae (known commonly as the Pine Family). This family of 232 individual species contains other familiar needle-leafed conifers such as Spruces, Firs, Larches, Hemlocks, and others in 11 separate genera. With 114 currently acknowledged species, the genus Pinus represents 49 percent of the species in the Pine family1. In Minnesota, the State Department of Natural Resources recognizes three pine species to be native, with numerous other species being grown in cultivated settings2. Around the world, Pinus species are native strictly to the northern hemisphere, with one exception (Pinus merkusii of the Indonesian highlands). They have been introduced into Oceana, Southern Africa, and South America for use in forest plantations and as ornamentals in gardens. Where they are not native some have become naturalized or even invasive, such as Pinus sylvestris (Scotch Pine) in the New England region of the continental United States3. The genus spans a wide variety of climactic conditions around the world, from the tropics to the boreal regions: from moisture-rich ecosystems to dry deserts.

In Minnesota, Pinus species are planted across the state. However, the native three native Pines (Pinus strobus, banksiana, and resinosa) can be found north and east of a line from Stearns County following the Mississippi River in the southern half of the state, and bordering the Red River Valley in the northwest3. Disjunct, native populations of Pinus banksiana (Jack Pine) populations can be found further south in Mankato3. The occurrence of native pines in the northern and eastern sections of Minnesota can be largely attributed to more acidic soils, higher rainfall, and cooler temperatures: conditions required by the species mentioned above4.

Pinus sylvestris. Engraving from Alymer Bourke Lamberts A description of the genus Pinus. 1824.


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For the northern parts of the state, the ideal growing conditions sustained immense old-growth forests of White Pine (Pinus strobus) until European settlement of Minnesota in the first half of the 19th century. As trappers were drawn to the territory by wild game, lumberman from Wisconsin ventured across the St. Croix river to harvest Pinus strobus in the 1830s. Thus began a nearly 100 year industry of harvesting Pinus strobus for the production of White Pine lumber in the state of Minnesota. Little of the original old growth forest remained by the time the last industrial producer of White Pine lumber had closed in 19295. At its peak around 1900, the industry in Minnesota annually produced 2.3 billion board feet of lumber from harvested Pinus strobus trees: enough to construct a 9 foot wide boardwalk that could circle the globe at the equator5.

While Pinus strobus was fortunate enough not to be made endangered by logging, many other Pinus species around the world have not recovered as smoothly or are currently under threat from habitat loss. It can therefore be seen as the duty of gardens, both public and private, to maintain collections of Pinus species in order to preserve endangered or rare species, as well as to evaluate varieties more common in cultivation6. At the University of Minnesota Landscape Arboretum in Chaska, Minnesota, it is the goal of the establishment to maintain diverse A train carrying Pinus Strobus (Eastern collections of as many genera as possible for White Pine) logs north of Brainerd, MN. evaluation in northern continental climates. The Photo by Northern Trackers Railroad Club. Circa 1900. Pinus collection at the Minnesota Landscape Arboretum (MLA) contains 200 individual plants, representing 20 species and 12 unique hybrids. In early 2012, the North American Plant Collections Consortium (NAPCC) of the American Public Garden Association officially recognized this pine collection at the Minnesota Landscape Arboretum7. This designation has elevated the Pinus collection to a new level: it is considered nationally a valuable source of genetic material and taxonomic diversity for the genus Pinus. Thus, the purpose of this book is to serve as a database for gardeners, collectors, and designers on ornamental Pinus species adaptable to Minnesota. Photographs were taken at the Minnesota Landscape Arboretum by the Author, unless otherwise noted.


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MorphologyPines are classified under the broad umbrella of Gymnosperms. The name Gymnosperm means naked seed, where the ovule is exposed at varying degrees to the environment before, during, and after fertilization in an open reproductive system. This is in contrast to Angiosperms, where the ovule is fully enclosed within an ovary creating closed reproductive system1. These open reproductive systems of Pines give them one of their distinctive features: cones. In the genus Pinus plants are monecious, wherein both male and female reproductive structures (cones) are present on the same plant. Pollination occurs in the spring when the smaller male cones, located near the top of the pine, begin to shed pollen. The pollen shed then drifts via the wind to receptive female cones, where the pollen adheres to a sticky fluid on the cone scales1. The actual fertilization process is much more complex, involving a twelve month period before separate fertilization of the embryo and megagametophyte (nutrient storage) are complete1. For someone observing a pine tree, this is the explanation for the presence of cones of different years being present on the same individual.

Pinus ponderosa male cones (top) and first year female cone (bottom). Photo by Kathy Merrifield, Science Photo Library.

The appearance of the pine seed within the cone varies depending on the species. Overall, the seeds are small with a winged edge to facilitate dispersion by the wind. There are some that rely on birds or small mammals to disperse seed, and thus these species have evolved seeds with large megagametophytes so as to become more palatable. Humans too have consumed pine nuts for thousands of years, with the species of choice being Pinus pinea (stone pine). Apart from species with larger seeds, the small size of pine seeds has enabled them to quickly colonize newly disturbed areas, often resulting in dense stands of a few or singe Pinus species.


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The needles, which are not unique to Pinus species, share similar traits with other conifers. These modified leaves contain a waxy cuticle to protect against desiccation in drought as well as during the winter for species that inhabit temperate regions. Stomata, or the pores where gases for photosynthesis are exchanged, are sunken below the surface of the needle to minimize water loss. These modifications enable many Pinus species to survive periods of drought stress if provided with ideal growing conditions during the rest of a growing season. Other adaptations specific to individual species abound in the genus. For example the cones of Pinus banksiana (Jack Pine) remain closed for years following maturation, only to open once the surrounding temperature reaches 140F to release viable seed. This adaptation allows P. banksiana to be a pioneer species after a fire in northern conifer woodlands, where nearly pure stands of seedlings can result in the decade following a major fire event2. Less species specific, casual observers will note the amount of pitch (sap) present on the limbs and trunks of certain Pinus species. There are indications that the sap from Pinus species prevents against fungal and bacterial infestation, and that secretion might be a defense mechanism by Pines to defend against pathogens3.

A colored Scanning Electron Micrograph (SEM) image of a pine needle. Notice the system of vascular bundles as well as the hooks on the side of the needle. These give certain pine needles their abrasive texture. Photo by Dr.Richard Kessel and Dr. Gene Shih, Science Photo Library .

Pinus strobus, resinosa, and banksiana with Betula papyrifera (Paper Birch) on a formerly disturbed site. Quetico Provincial Park, Ontario.


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Species ProfilesSubgenus Ducampopinus

Pinus aristata (Bristlecone Pine)Range: High altitudes in the mountains of Colorado, New Mexico, and Arizona. Needles: In clusters of 5, bluish-green in color. 1-1 long. Will stay on the tree for 17 years. Size: 5-10 under Minnesota conditions, can grow to 30 in the wild. Hardiness: Zones 4-7. Likely intolerant of high humidity. Growth Habit: Ancient plants in the wild possess a beautiful windswept appearance: those in cultivation in the upper Midwest will never attain this but the trees are nonetheless interesting. Slightly pendulous branches. Growth Rate: Very slow. The pictured tree was grown from seed in 1962 and after 40 years is only 6 feet tall. Texture: Medium Cones: Brown when mature, 2-4 long by 1 in diameter. Cultural Notes: A unique specimen pine for Minnesota landscapes. The tree would lend itself very well to any conifer collection or rock garden. Shade will cause a decline in the vigor of Bristlecone Pines, as a evidenced in some specimens at the Minnesota Landscape Arboretum. The pine should succeed on rocky, difficult soils.


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Pinus aristata (Bristlecone Pine)

Top: P. aristata habit Inset: P. aristata foliage MNLA Accession Number : 19620080 Planted from seed in 1962, transplanted to current location in 1971


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Species ProfilesSubgenus Pinus

Pinus banksiana (Jack Pine)Range: North America from the Arctic circle, southeast to Minnesota and the Great Lakes of the United States. Needles: In clusters of 2. Length varies from to 2 depending on growing conditions and regional variation. Olive-green during the growing season, becoming yellow during the winter. Size: 35 to 50 in height. Average spread about 25. Hardiness: Zones 2-6. One of the most cold hardy pines. Growth Habit: In pure stands and confined spaces, Jack pine assumes a more upright habit. As a specimen, the tree spreads more: irregular branches sometimes make the tree appear shrubby. Growth Rate: Dirr describes the rate as Slow-medium, however new seedlings in burn over areas seem to grow very fast in youth. Texture: Coarse Cones: 1-2 long, very irregular in shape but generally possess a bend in the cone towards the tip. Gray when mature, however the cones dont open unless exposed to 140F. Cultural Notes: Not the most ornamental tree, however selections have been made for weeping and prostrate varieties. A good pine for difficult sites, Jack Pine can tolerate poor soils that would cause other pine species to languish. Use as a windbreak, screen, or naturalized area.


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Pinus banksiana (Jack Pine)

Top: P. banksiana habit Inset: P. banksianaa foliage and immature cones


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Pinus contorta (Lodgepole Pine)Range: Along the Pacific Coast from southeastern Alaska to northern California, inland to southern Yukon Territory and British Columbia in Canada, east to Montana, Wyoming, and Colorado in the United States. Needles: In clusters of 2, 1 long. Dark green with a twisting habit. Size: Great variation depending on seed source: those from coastal areas are much shorter while those inland can grow to 100 or more. Under cultivation in Minnesota, 30 can be expected. Hardiness: Again varies with seed source. Trees from the Pacific coast arent entirely hardy below Zone 6, while inland sources can likely be given a zone 4 designation. Growth Habit: Varies, Pacific coast trees are smaller and more contorted, while inland trees are very erect and tall. Minnesota growers can expect something in between. Growth Rate: Fast in its native habitat, slow under Minnesota conditions. Texture: Medium. Cones: 1 in length, 1 in width. Gray in color when mature, can remain on the tree for several years. Cultural Notes: There are better pines for Minnesota climates, however obtaining plants from inland sources will help in terms of landscape adaptability. The tree maintains a manageable size under cultivation at the Minnesota Landscape Arboretum, however few characteristics present on trees in habitat seem to translate to the upper Midwest. Provide well drained, humus-rich soils for best results in the upper Midwest.


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Pinus contorta (Lodgepole Pine)

Top: P. contorta habit Inset: P. banksianaa foliage MNLA Accession Number: 19730251 Transplanted to current location in 1973.


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Pinus densiflora (Japanese Red Pine)Range: Japan, Korea, northeastern China, far southeastern Russia. Needles: In clusters of 2, 3-5 in length, remaining 3 years. Light to dark green in color, very reflective in sunlight. Size: 20-60 in height, dependent on seed source. Hardiness: Zones 3b-7. Hardy strain for Minnesota evaluated at the Forestry Experiment Station in Cloquet, MN. Growth Habit: An irregular grower with crooked branches, however this can be an attribute. The pictured tree at the Minnesota Landscape Arboretum displays an interesting, floppy appearance. Growth Rate: Slow. Texture: Medium. Cones: 1 -2 in length by 1 in diameter. Mustard-yellow, opening in the 2nd year and remaining on the tree for 2-3 more years. Cultural Notes: A very interesting specimen pine that has a future in Minnesota landscapes. The floppy growth and contorted branches add interest to the landscape, while flaking red bark adds winter interest against the snow cover. The tree does not appear to be very particular about growing conditions, however provide full sun to realize the plants unique form.


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Pinus densiflora (Japanese Red Pine)

Top: P. densiflora habit Inset: P. densiflora foliage MNLA Accession Number: 19720421 Transplanted to current location in 1972.


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Pinus mugo (Mugo Pine)Range: Southern Europe from Pyrenees Mountains in the west, throughout the Alps, and east to the Balkan peninsula. Needles: In clusters of 2, 1-2 long remaining 5 years. Dark green in color, rigid. Size: Great variation depending on seed source and cultivar, 10-15 in height with equal spread under cultivation can be expected. Hardiness: Zones 3-7. Growth Habit: Again variable depending on seed source and cultivar, some mature seed grown plants at the Arboretum are very spreading, while others possess upright, stiff branches. Growth Rate: Slow. Texture: Medium-Coarse. Cones: Short and rounded, sometimes present in pairs of 2 or 3. 1-2 in length, nearly equal in diameter. Dark gray in color at maturity. Cultural Notes: A very common landscape pine due to the large amount of cultivars available on the market. Prostrate, dwarf, and pyramidal selections all exist. Mugo pine is well suited as a foundation plant in cold climates, or as a specimen where a dwarf pine is needed. Has good salt tolerance, and can be used along roadways where salt spray is an issue. Purchase cultivated varieties, as numerous variation in height and habit is present within the species.


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Pinus mugo (Mugo Pine)

Top: P. mugo habit Inset: P. mugo foliage MNLA Accession Number: 19660854 Planted from seed in 1966, Transplanted to current location in 1971.


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Pinus nigra (European Black Pine)Range: Two major distribution in Europe, North Africa, and Asia Minor. The first group is located in the mountains of Spain, southern France, and northern Algeria. The eastern group inhabits the mountains of Italy, Austria, the Balkan peninsula, and Turkey. Needles: In clusters of 2, 4-6 long remaining 4 years. Dark green, very stiff with a sharp point on the end of the needle. Waxy appearance. Size: 50-60 under cultivation with around 30 of spread. Hardiness: Zones 3b-7. Growth Habit: Pyramidal in youth, becoming less so with age. Young trees can have a shrubby appearance, while older trees tend to loose their lower branches. Growth Rate: Medium. Texture: Coarse. Cones: Single or in pairs of 2-3, 2-3 in length by 1 in diameter. Light brown after the first year, turning darker brown before opening. Cultural Notes: Another very common pine in Minnesota landscapes. Has proven very susceptible to Diplodia tip blight. However, the European Black Pines adaptability to difficult landscape situations has assured its continued use. The tree requires well drained soil: have observed trees in wet situations that succumbed to various pathogens. Black Pine seems to do very well in urban environments, and tolerates salt spray from roadsides. Overall, a very hardy tree despite is ubiquity.


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Pinus nigra (European Black Pine)

Top: P. nigra habit Inset: P. nigra foliage and first year cones MNLA Accession Number: 19900800 Transplanted to current location in 1990.


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Pinus ponderosa (Ponderosa Pine)Range: Western North America, from British Columbia to northern Mexico. Extensive populations can be found in Northern California in the Sierra Nevada and Rocky mountains. East to the Black Hills of South Dakota and western Nebraska. Needles: In clusters of 2, 5-9. Dark yellowish green, very stiff with a sharp point on the end of the needle. Similar to Pinus nigra Size: Up to 200 in the wild, 50-80 under cultivation with around 30 of spread. Hardiness: Zones 3-7, does not tolerate humidity well. Growth Habit: Open in youth, upright with age. Branches will begin to droop towards the ground as the tree matures, creating an interesting habit. Growth Rate: Medium-Fast. Texture: Coarse. Cones: In pairs of 2-3, 3-4 in length by 3 in diameter. Maturing in 2 years, light brown with spines at the end of the scales. Cultural Notes: Ponderosa Pines should be grown in a sunny spot with plenty of room to grow. The bark on old trees is very ornamental, with large plates of bark developing a reddish color. While the red color rarely develops in Minnesota, the coarse bark is nonetheless ornamental. Tolerant of drought, alkaline soils, and salinity.


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Pinus ponderosa (Ponderosa Pine)

Top: P. ponderosa habit Inset: P. ponderosa foliage and mature cones MNLA Accession Number: 19620611 Started from seed in 1962. Transplanted to current location in 1964.


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Pinus resinosa (Red Pine)Range: Nova Scotia and New Brunswick, west through Quebec and Ontario, south through northern Minnesota and Wisconsin. Needles: In clusters of 2, 5-7. Green, very brittle needles. Needle bases are white with orange sheaths. Size: 60 to 100. Can grow very tall, even under cultivation Hardiness: Zones 2-6. Growth Habit: Open in youth, upright with age. Branches will begin to droop towards the ground as the tree matures, creating an interesting habit. Growth Rate: Medium. Texture: Medium. Cones: In pairs of 2-3, 3-4 in length by 3 in diameter. Maturing in 2 years, light brown with spines at the end of the scales. Cultural Notes: An easy to grow native pine. Not particularly ornamental, except for the reddish bark on mature trees for which the tree is named. In Minnesota the tree is endemic to sandy and rocky well drained soils. Have observed the tree growing on rock outcroppings in northern Minnesota. A good tree for privacy screens or difficult soil.


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Pinus resinosa (Red Pine)

Top: P. resinosa habit Inset: P. resinosa foliage MNLA Accession Number: 19630586 Started from seed in 1963. Transplanted to current location in 1965.


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Pinus rigida (Pitch Pine)Range: Northeastern North America, from coastal southern Maine south through New Jersey, southwest through the Appalachian Mountains. Needles: In clusters of 3, 2.5-5 in length. Light green needles with a waxy appearance: often appearing on adventitious meristems on the branches and trunk. Size: Variable depending on growing conditions, 10-100 in the wild, 30-40 in cultivation. Hardiness: Zones 4-7. Growth Habit: Prostrate on rocky soils and shorelines, becoming upright on deeper soils with drooping branches. Growth Rate: Medium. Texture: Medium. Cones: In pairs of 3-5, 2 in length by 2 in diameter. Maturing in 2 years. Cultural Notes: A common pine on the New England coast, have observed plants growing in sand dunes on Cape Cod that were prostrate in habit: plants further from the ocean assume an upright habit. The species prefers acidic sandy soil, however plants at the Minnesota Landscape Arboretum are faring well. Very salt tolerant, good for planting near roadsides where salt treatment in the winter is common.


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Pinus rigida (Pitch Pine)

Top: P. rigida habit Inset: P. rigida foliage MNLA Accession Number: 19621059 Started from seed in 1962. Transplanted to current location in 1965.


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Pinus sylvestris (Scots Pine)Range: A very wide distribution spanning from the Atlantic coast of Spain in the east, west to northern China and western Siberia. Needles: In clusters of 2, 2-5 in length. Blue-green in color with a white line: much variation on needle color within the species. Size: 50-100, rarely to 100 under cultivation. Hardiness: Zones 2-7. Growth Habit: Broad and spreading for the species with low lateral branches, becoming thinner with age. Numerous cultivars exist with dwarf, upright, and prostrate forms. Growth Rate: Medium. Texture: Medium. Cones: Solitary or in pairs of 2-3, 1-3 in length. Maturing in 1.5 years, with mature cones falling from the tree. Cultural Notes: An ornamental pine for cold climates; ubiquitous in northern climates. The peeling orange bark, blue-green needles create a nice contrast and are perhaps the species greatest attributes. The peeling bark is not observed on trees until they reach approximately 15 years in age. The broad habit of the tree suits itself well for use as a screen, and the ornamental bark and needles provide winter interest.


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Pinus sylvestris (Scots Pine)

Top: P. sylvestris habit Inset: P. sylvestris ornamental bark. MNLA Accession Number: 19600399 Started from seed in 1960. Transplanted to current location in 1965.


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Species ProfilesSubgenus Strobus

Pinus cembra (Swiss Stone Pine)Range: French Alps in the west, East to Bulgaria and Turkey. South into Italy and the Balkan Peninsula. Needles: In clusters of 5, 2-5 long remaining 5 years. Green upper halves with a bluish underside. Relatively stiff, some flexibility. Size: Rarely more than 40 under cultivation, larger specimens present in the wild. Hardiness: 3b-7, likely not tolerant of high humidity. Growth Habit: Columnar for the first 10 years, becoming more broad and bushy as the tree ages. Cultivars exist where the tree maintains this columnar form beyond the juvenile stage. Growth Rate: Slow. Texture: Medium. Cones: Short and blunt, 2-3 long by 1.5-2 in diameter. Scales are brown-violet when mature. Seed release does not occur until the spring of the 3rd year following pollination. The seed is very large (up to 0.5) and can be consumed as a pine nut. Cultural Notes: A currently underused species in Minnesota landscapes. The manageable growth habit is well suited to cultivated environments, and the slow growth allows the tree to maintain its manageable size. It thrives in full sun and is tolerant of roadside environments.


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Pinus cembra (Swiss Stone Pine)

Top: P. cembra habit Inset: P. cembra foliage MNLA Accession Number: 19610493 Transplanted to current location in 1961.


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Pinus koraiensis (Korean Pine)Range: North and South Korea, Japan, northern China, and eastern Russia. Needles: In clusters of 5, 3-5 long. Greenish-white in color with a soft appearance. Curling is often present at the end of the needles. Size: 30-50 under cultivation, can grow to 100 in the wild. Hardiness: Zones 3-7. Growth Habit: Slightly pyramidal in youth, becoming more open and irregular with age: similar to P. strobus in habit. Older specimens at the Minnesota Landscape Arboretum can be difficult to distinguish from P. strobus. Growth Rate: Slow. Texture: Medium. Cones: Pendant, solitary or in groups of 3. 3-7 in length and light brown in color, maturing in 1.5 years. Seeds are large (around in all dimensions) and do not possess a wing. Cultural Notes: An uncommon tree in Minnesota landscapes, but perfectly adaptable. This hardy pine is similar to P. strobus except for a slight curling in mature needles. In youth, Korean Pine has a more open and fine-textured appearance than P. strobus.


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Pinus koraiensis (Korean Pine)

Top: P. koraiensis habit Inset: P. koraiensis foliage MNLA Accession Number: 19720241 Transplanted to current location in 1972.


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Pinus strobus (Eastern White Pine)Range: Newfoundland in the East to Northwestern Minnesota in the west, North to central Ontario and Quebec and south along the Great Lakes, with extensive populations in the Appalachian mountains as far south as Georgia at high elevations. Needles: In clusters of 5, 2-5 long, remaining for 2 years. Soft, lacy appearance: bluegreen in color. Color varies geographically. Needles on exposed branches will bunch together if exposed to severe cold and dryness during the winter. Size: 50 to 80 under landscape conditions, 150 or more in the wild. Hardiness: Zones 3-8. Growth Habit: Bushy in youth, becoming more open with age. Branches grow roughly parallel to the ground and are more plentiful towards the top, especially on older trees. Growth Rate: Medium-Fast. Texture: Fine. Cones: Pendant, 3-7 inches long by 1.5 inches in diameter. Symmetrical, maturing in the second year. Cultural Notes: A very versatile pine for Minnesota landscapes. Its fast growth makes it suitable for a shade tree or screen. For gardeners who have the space, this climax species will provide beauty and foundation for any landscape. Needles will be burned by road salt in the winter, resulting in death of the lower limbs.


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Pinus strobus (Eastern White Pine)

Top: P. strobus habit Inset: P. strobus foliage MNLA Accession Number: 19601198 Started from seed in 1960. Transplanted to current location in 1965.


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CultivationMinnesota is fortunate enough to have a climate in which pines are native, and where a large variety of species can be grown. The genus has often been a staple in Minnesota landscapes due to its evergreen nature, providing tremendous interest to gardens during the winter months. For some species (P. banksiana, P. nigra, and P. strobus), bushy habits during youth lend these species well to being windbreaks or privacy screens. Other individuals with ornamental traits (ie dwarf stature, colored needles, etc) have been introduced into commerce and sold as specimen plants for home gardeners. As landscape plants, Pines and their cultivars can easily fit most niches within the home garden.

Cultivated Pines at the Minnesota Landscape Arboretums Pine Collection

The greatest limiting factor to Pine cultivation in Minnesota aside from cold hardiness is soil: specifically the microorganisms present and pH. Pines do not thrive in the heavy, alkaline clay soils present in the western half of the state. The root systems of most pines are fairly fibrous, resulting in a stunted root system when cultivated on heavy soils. Pine roots themselves rely on specific fungi (Micorrhizae) present in light, organic soils known as humus. These fungi form a symbiotic relationship with the pine roots: the pine provides the fungus with sugars from photosynthesis while the fungus makes additional nutrients available to the pine. In soils typical of the western half of the state, these fungi


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Where the soils are not heavy, pine cultivation is straightforward. After planting in an appropriate soil, provide the trees with ample water. The fibrous root system may take a couple of years to establish fully, leaving the trees are especially prone to drought stress during this time. Fertilizer should rarely be applied, as the chemicals have the potential to disturb the delicate micorrhizal-root relationship. Ideally, pines growing in a humus-rich soil will have all nutrients made available to them by the Micorrhizal fungi. All pines that can be grown in Minnesota generally prefer sunny situations, however many will tolerate partial shade. Those grown under shady conditions will be more elongated, and may not possess as rich of a needle color. If grown properly pines will be more vigorous, resistant to disease, and have optimal appearance. They are not as picky when it comes to cultivation, and thus are very versatile in the home landscape.

Photos: Cultivated dwarf pines and other conifers at the University of Minnesota Landscape Arboretums Conifer Collection.


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Common DiseasesCourtesy of the University of Minnesota Extension Brown spot, Mycosphaerella dearnessi Symptoms: Most pine, esp. Scots and ponderosa. Spots that enlarge to bands and encircle the needle develop in late July and August. Diseased needles often have dead tips. Killed needles drop late in the fall. Treatment: Allow for adequate spacing and avoid shearing and other operations when foliage is wet. CHEMICAL: Mancozeb. Dothistroma needle blight, Mycosphaerella pini Symptoms: Two-and three-needled pines are affected but most common on Austrian pine. Chlorotic spots appear on infected needles in fall and winter. Spots spread, turn red/brown and girdle needles causing the distal end to die. Black fruiting bodies break through lesion surface in spring. Defoliation can be severe. Treatment: Remove the lowest whorl of branches on young trees. Clean out debris and weeds in and around trees. Space plants for good air circulation. Avoid planting in low-lying areas with poor drainage. Growers should shear trees during dry weather. CHEMICAL: Bordeaux (8-8-100). Can be toxic to new needles. Needlecast, Lophodermium seditiosum Symptoms: Two-and three-needled pines, esp. Austrian red and Scots pine. Current season foliage develops yellow spots which turn brown with yellow margins in late fall and spring. Black, elliptical fruit bodies mature in or just beneath the epidermis in late summer. Needles brown and drop. Twigs die back. Spores are released during late summer/early fall rains with most infection occurring in August and September. Treatment: Improve air circulation with thinning and pruning: cool moist environments favor infection. CHEMICAL: Nurseries should apply mancozeb plus a spreader sticker or chlorothalonil. Make 3-4 applications starting July 1.


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Pine needle rust, Coleosporium sp. Symptoms: Two-and three-needle pines develop light-colored blisters which burst open to release yellow/orange spores in early summer. These spores infect the alternate hosts aster and goldenrod and NOT pine. Treatment: Damage is seldom detrimental. Remove or mow goldenrod and aster plants in the immediate vicinity. CHEMICAL: None recommended. Pine-oak gall rust or eastern gall rust, Cronartium quercuum Symptoms: Two-and three-needled pines are susceptible. The alternate host is red oak. Globose swellings up to 10 inches in diameter form on pine branches. Yellow/orange powdery-appearing spores form on the gall surface in early summer. Treatment: Remove galls on pine branches preferably before spring. CHEMICAL: None recommended. However, if the situation warrants, mancozeb may be applied when yellow pustules form on pine galls. Pine-pine gall rust or western gall rust, Endocronartium (Peridermium) harknessii Symptoms: Two-needled pines, especially mugho, ponderosa, red and Austrian pine. There is no alternate host. Rough, globose galls appear on branches and trunk. Yellow/ orange powdery spores form on the gall surface in early summer. Treatment: Remove galls on infected trees. Remove all trees with galls for a distance of 300 yards around nurseries and cull infected seedlings. CHEMICAL: Mancozeb when yellow spores are present on galls. Shoot (Diplodia) blight, Sphaeropsis sapinea Symptoms: New shoots are invaded and killed in the spring, usually before needle expansion is complete. Needles turn brown; resin soaking is common. Dieback may progress into main stem. Fruiting bodies form at the base of infected needles, on twigs and on second year cones. Austrian pine is extremely susceptible after reaching cone-bearing age. Treatment: Keep landscape trees well watered and stress free. Thin forest stands. Avoid shearing during wet weather or high humidity. Plant less susceptible pine species. CHEMICAL: Benomyl, thiophanate-methyl. Begin when new growth starts. Use a spreader sticker. Also Bordeaux.


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White pine blister rust, Cronartium ribicola Symptoms: Five-needled pines are susceptible (eg. eastern white pine, limber pine). Elongate cankers with abundant pitch flow develop on trunks and branches causing branch dieback or flagging. White blisters containing yellow/orange spores break through the cankered areas in the spring. Spores produced on pine infect the alternate host, Ribes species. Treatment: Minimize use of white pine on sites with high blister, rust hazard ratings. Avoid planting currants and gooseberries in the vicinity of white pine. Remove the lower branches on large trees. Scout trees annually for early infection and remove infected branches. CHEMICAL: Triadimefon. European Pine Sawfly, Neodiprion sertifer Symptoms: Larvae consume the previous years needles on a single branch before moving on to other branches. Look for barren branches under the new years growth, and for small white egg sacs on the needles. Treatment: Apply horticultural oil on young larvae, otherwise no treatment is recommended for mature larvae.


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BibliographyIntroduction 1http://www.conifers.org/pi/Pinus.php, 2http://www.dnr.state.mn.us/forestry/education/treeforallseasons/nativetrees.ht ml 3http://plants.usda.gov/java/profile?symbol=PISY4SOILS

AND LANDSCAPES OF MINNESOTA

5http://www.mnhs.org/places/sites/fhc/logging.html

6http://www.arboretum.umn.edu/aboutus.aspx

7http://www.publicgardens.org/content/what-napcc

Morphology 1P. Raven, R. Evert, and Susan Eichorn. The Biology of Plants, pgs 363-369 2 M. Dirr, Manual of Woody Landscape Plants . 5th Edition, pg 729 3P. Raven, R. Evert, and Susan Eichorn. The Biology of Plants, pg 533 Species Profiles 1M. Dirr, Manual of Woody Landscape Plants . 5th Edition, pgs 728-740 2The Gymnosperm Database. http://www.conifers.org/pi/Pinus.php Common Diseases 1http://www.extension.umn.edu/distribution/horticulture/dg6659.html

Documents

Pinus: Their Cultivation in Minnesota