Tree-of-heaven (ToH), also known as Chinese sumac, varnish tree, or stink tree, is a large, rapidly growing deciduous tree native to parts of China. Tree-of-heaven was introduced to North America as early as the late 1700s and has since become invasive in most areas of the United States. Tree-of-heaven can be found, sometimes in abundance, in both urban and rural environments. The tree spreads through abundantly produced wind-scattered seeds from female trees, and sprout colonies arising from established trees, in some cases producing monoculture stands of the species. ToH has also been shown to produce allelopathic chemicals that can inhibit the growth of neighboring plants, providing an additional competitive advantage.
Tree-of-heaven is a serious threat as an invasive species in many habitats or untended areas. It can reach 80 feet or more, its growth rate outpaces most native tree species, and wind scatters seeds that female trees produce in abundance. Controlling ToH is a challenge. In this publication, Purdue University extension specialists and property managers explain herbicide options, application techniques and strategies to control and manage ToH.
To receive the free download visit the Purdue Extension’s resource center: The Education Store – Invasive Plant Series – Tree of Heaven, Ailanthus altissima.
View Forestry and Natural Resources (FNR) YouTube Video: ID That Tree: Invasive Tree of Heaven.
Resources:
Invasive Species, Playlist, Purdue Extension – FNR YouTube Channel
Report Invasive Species, Purdue Invasive Species
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Invasive plants: Impact on Environment and People, The Education Store, Purdue Extension’s resource center
A Woodland Management Moment, Playlist, Purdue Extension – Forestry and Natural Resources (FNR) Youtube Channel
Conservation Tree Planting: Steps to Success, Purdue Extension – FNR Youtube Channel
Forest Improvement Handbook, The Education Store
Tree Risk Management – The Education Store, Purdue Extension’s resource center
Investing in Indiana Woodlands, The Education Store
Woodland Invaders, Got Nature? Blog, Purdue Extension – FNR
Indiana Department of Natural Resources: Invasive Species
Invasive Plant Species Identification, Video, Purdue Extension – FNR Youtube Channel
Mile-a-minute Vine, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement & Regeneration Center (HTIRC) & Purdue University Department of Forestry and Natural Resources
Ron Rathfon, Regional Extension Forester, Sourthern Indiana Purdue Agriculture Center (SIPAC)
Purdue Forestry and Natural Resources
MyDNR, Indiana’s Outdoor Newsletter: The Indiana Cooperative Fish and Wildlife Research Unit, or CRU, that Purdue will host, brings together the U.S. Geological Survey, U.S. Fish and Wildlife Service, Purdue University, the DNR, and the Wildlife Management Institute.
Its focus will be on delivering actionable science addressing fish, wildlife, plants, and other natural resources in Indiana and beyond, including the connection between the health of wildlife and the health of people.
The CRU Program is results focused, bringing together natural resource managers and researchers to work as a team to address the most pressing natural resource management needs with science. As such, the partnerships formalized with the creation of CRUs lead to true co-production of research.
“The creation of this new unit is another milestone in the highly successful USGS Cooperative Research Units Program, and we are proud to join the state of Indiana, Purdue University, the USGS, Wildlife Management Institute, and others to address conservation questions facing Indiana and the region,” said U.S. Fish and Wildlife Service Science Applications Program Assistant Regional Director Craig Czarnecki. “We look forward to engaging with the students and professionals at Purdue University as we co-develop scientific research and support the next generation of conservationists.”
But CRUs don’t just tackle management needs. They do so while cultivating the next generation of scientists and resource managers. The new Indiana CRU will focus on education, training, and outreach related to natural resources vital not only to Indiana, but the Midwest and regional economies as well.
Like all CRUs, the Indiana CRU will consist of 2-5 federal scientists along with graduate students, postdoctoral fellows, and administrative specialists. Federal scientists will serve as faculty at Purdue University, teaching graduate-level courses, supervising graduate students and postdocs, offering workshops for students and cooperators, and conducting research on natural resources topics. Once created, each CRU formalizes research priorities, like aquatic conservation or wildlife disease. Indiana CRU partners will decide these in the coming months.
“We look forward to the tremendous opportunity that collaboration with the Indiana CRU will bring to our state and Purdue University,” said Karen Plaut, executive vice president of research at Purdue University. “It will have a direct impact on graduate education as well as research productivity and innovation.”
For full article please visit: The partnership is Indiana’s first U.S. Geological Survey Cooperative Fish and Wildlife Research Unit, Indiana DNR Calendar.
Sign up to receive the MyDNR Newsletter by email: MyDNR Email Newsletter
Resources:
Purdue Announces New USGS Cooperative Research Unit, Purdue Agriculture New
Wildlife Habitat Education Program: Wildlife Identification Guide, The Education Store, Purdue Extension resource center
Wildlife Habitat Education Program – Teaching and Learning Wildlife Management Practices, The Education Store
Wildlife Habitat Evaluation Program: Preparing for the Wildlife Challenge, The Education Store
Developing a Wildlife Habitat Management Plan, The Education Store
Woodland Wildlife Management, The Education Store
Purdue Integrated Deer Mangement Project, Purdue College of Agriculture
Purdue Extension-Forestry and Natural Resources (FNR) Publications
Indiana Pond Fish, Species Identification Card Set, Purdue Extension – Forestry and Natural Resources (FNR)
A Guide to Small-Scale Fish Processing Using Local Kitchen Facilities, The Education Store
Subscribe to Purdue Extension-FNR YouTube Channel
Invasive Species, Playlist, Purdue Extension – FNR YouTube Channel
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Invasive plants: Impact on Environment and People, The Education Store, Purdue Extension’s resource center
Indiana Department of Natural Resources, Department of Fish & Wildlife
Purdue Landscape Report: Stop me if you’ve heard this one…. A tree is in a slow decline year after year. You are called to your client’s property only to find the root flare well below grade.
Most professionals in the Green Industry have encountered this at some point in their career. The most common reason for the slow decline of trees in the landscape is due to the depth of planting and girdling roots. Deep planting can cause a number of deleterious problems, including an increase in circling/girdling roots restricting vascular tissue and decay of protective bark (Fig. 1). The vascular tissue in the bark is located on the outer portions of the trunk, while the anatomy of roots contains the vascular tissue in the center. This is why roots can graft with roots and stems can graft with stems, but also why roots can girdle the stems of trees (Fig. 2)
Excessive mounding of mulch (aka volcano mulch) (Fig. 3) can contribute to tree decline, very similar to a tree planted too deep. It’s important to remember that keeping mulch several inches away from the trunk is imperative in tree health.
If a newly transplanted tree is planted significantly too deep, a faster decline can occur, especially in plants that can’t tolerate ‘wet feet’ (aka too much soil moisture) (Fig.4). In heavy-clay soils, the negative effects on tree health increase by creating a bath-tub situation by water not draining expeditiously after a rainfall or irrigation event.
To view this full article and other Purdue Landscape Report articles, please visit Purdue Landscape Report.
Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.
Resources:
The Purdue Landscape Report
Planting Your Tree Part 1: Choosing Your Tree, Purdue Extension YouTube Channel
Summer Tree Care, Purdue Landscape Report
Tree Defect Identification, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Surface Root Syndrome, The Education Store
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store
Ask an Expert: Tree Selection and Planting, Purdue Extension-Forestry & Natural Resources (FNR) YouTube playlist
ID That Tree, Purdue Extension-FNR YouTube playlist
Subscribe – Purdue Extension-FNR YouTube Channel
Kyle Daniel, Commercial Landscape and Nursery Crops Extension Specialist
Purdue Horticulture & Landscape Architecture
In this episode of ID That Tree, Purdue Extension forester Lenny Farlee introduces the Black Spruce. This species is found in bogs, wetlands, and sometimes dry sites within the North Woods of Upper Michigan and Wisconsin. Black Spruce has a bluish cast to the newest needle growth. It has single needles attached to the twigs that are typically less than an inch long. The twigs have a reddish brown cast. This tree also has small cones that are somewhat egg shaped.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Resources:
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Invasive Species Playlist, Playlist, Purdue Extension – FNR YouTube Channel (Asian Bush Honeysuckle, Burning Bush, Callery Pear, Multiflora rose)
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
How long do seeds of the invasive tree, Ailanthus altissima remain viable? (Invasive Tree of Heaven), USDA Forest Service
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Episode 11 – Exploring the challenges of Invasive Species, Habitat University-Natural Resource University
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store, Purdue Extension Resource Center
Native Trees of the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources
In this episode of ID That Tree, Purdue Extension forester Lenny Farlee introduces the Quaking Aspen. This species is found in the North Woods of Northern Wisconsin, Northern Indiana, and the Upper Peninsula of Michigan. This species has simple, alternately arranged leaves. The stems are flat which allow them to quake or tremble in the wind. The stems on this species are relatively stout and have a chalky white color.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Resources:
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Quaking Aspen, Native Trees of Indiana River Walk, Purdue Fort Wayne
Invasive Species Playlist, Playlist, Purdue Extension – FNR YouTube Channel (Asian Bush Honeysuckle, Burning Bush, Callery Pear, Multiflora rose)
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
How long do seeds of the invasive tree, Ailanthus altissima remain viable? (Invasive Tree of Heaven), USDA Forest Service
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Episode 11 – Exploring the challenges of Invasive Species, Habitat University-Natural Resource University
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store, Purdue Extension Resource Center
Native Trees of the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources
In this episode of ID That Tree, Purdue Extension forester Lenny Farlee introduces the Chokecherry. This species is found in the North Woods of Northern Wisconsin and the Upper Peninsula of Michigan as well as natively in Indiana in small/medium shrub form. This species has alternately held broad leaves with finely toothed margins, and has short leaf stalks. The stems are a light to medium gray color and have prominent lenticels scattered along them.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Resources:
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Invasive Species Playlist, Playlist, Purdue Extension – FNR YouTube Channel (Asian Bush Honeysuckle, Burning Bush, Callery Pear, Multiflora rose)
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
How long do seeds of the invasive tree, Ailanthus altissima remain viable? (Invasive Tree of Heaven), USDA Forest Service
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Episode 11 – Exploring the challenges of Invasive Species, Habitat University-Natural Resource University
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store, Purdue Extension Resource Center
Native Trees of the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources
In this episode of ID That Tree, Purdue Extension forester Lenny Farlee introduces the White Spruce. This species is found in the North Woods of Northern Wisconsin and the Upper Peninsula of Michigan. This species has single needles attached to the twig that tend to be relatively angular and stout. The bark tends to be flaky and dark. The cones are two to three inches in length, have thin scales, and are cylindrical in shape.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Resources:
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Invasive Species Playlist, Playlist, Purdue Extension – FNR YouTube Channel (Asian Bush Honeysuckle, Burning Bush, Callery Pear, Multiflora rose)
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
How long do seeds of the invasive tree, Ailanthus altissima remain viable? (Invasive Tree of Heaven), USDA Forest Service
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Episode 11 – Exploring the challenges of Invasive Species, Habitat University-Natural Resource University
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store, Purdue Extension Resource Center
Native Trees of the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources
Purdue Landscape Report: Poison hemlock was introduced to North America as a garden/ornamental plant. It is a native of Europe, and it is a member of the Apiaceae (parsley) family.
Purdue experts Bill Johnson and Marcelo Zimmer wrote about poison hemlock in a Purdue Pest & Crop newsletter.
They wrote that poison hemlock can be noticed very early in the spring every year, as it is typically one of the first weeds to green up, usually in late February to early March if temperatures are favorable. They said the largest threat of this weed is the toxicity of its alkaloids if ingested by livestock or humans, but it can also reduce the aesthetic value of landscapes and has been reported to creep into no-till corn and soybean fields as well.
Purdue Extension’s fact sheet on poison hemlock states that it can also be found along roads, streams, trails, ditches, forest edges, and waste areas.
The Purdue experts said that poison hemlock is a biennial weed that exists as a low-growing herb in the first year, and bolts to three to eight feet tall in the second year, when it produces flowers and seed. It is often not noticed until the bolting and reproductive stages of the second year. Poison hemlock is often confused with wild carrot, but can be distinguished by its lack of hairs and purple blotches that occur on the stems.
The experts pointed out that poison hemlock contains five alkaloids that are toxic to humans and livestock, and it can be lethal if ingested. They warn that the plant’s alkaloids may also be absorbed through the skin, so if you find yourself hand-pulling poison hemlock, it would be a good idea to wear gloves. All parts of the plants contain the toxic alkaloids with levels being variable throughout the year. Symptoms of toxicity include nervousness, trembling, and loss of coordination followed by depression, coma, and/or death. Initial symptoms will occur within a few hours of ingestion.
For history buffs, the Greek philosopher Socrates was sentenced to death by hemlock poisoning.
Cases of poisoning due to poison hemlock ingestion are rare as the plants emit a mousy odor that makes it undesirable and unpalatable to livestock and humans. Consumption and toxicity in animals usually occur in poorly managed or overgrazed pastures where animals are forced to graze poison hemlock because desirable forage is lacking.
To view this full article and other Purdue Landscape Report articles, please visit Purdue Landscape Report.
Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.
Resources:
The Purdue Landscape Report
Purdue Pest & Crop Newsletter
Invasive Plant Species Fact Sheets: Poison Hemlock, The Education Store, Purdue Extension Resource Center
Poison Hemlock (Conium maculatum), United States Department of Agriculture (USDA)
Invasive plants: impact on environment and people, The Education Store, Purdue Extension’s resource center
Woodland Management Moment: Invasive Species Control Process, Video, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel
Invasive Species, Playlist, Purdue Extension – FNR YouTube Channel
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Report Invasive, Purdue College of Agriculture – Entomology
John Woodmansee, Extension Educator, Whitely County
Purdue Extension
In this webinar hosted by Indiana Forestry & Woodland Owners Association, ecologist Michael Homoya discusses the many naturally occurring species of orchids in Indiana and their range, habitats and blooming seasons. This presentation will look at a selection of them and discuss their floral characteristics as well as range, habitat, and blooming seasons. Michael Homoya served as Botanist/Plant Ecologist for the Indiana Department of Natural Resources, Division of Nature Preserves for 37 years before retiring in 2019. He has written over 75 scientific papers, popular articles, and books about Indiana’s natural features, including Orchids of Indiana, Wildflowers and Ferns of Indiana Forests: A Field Guide, Wake Up, Woods, and Wildflowers of the Midwest.
Check out the Indiana Forestry & Woodland Association YouTube Channel for videos including: What is IFWOA?; A New Carbon Program for Hardwood Landowners Webinar, Indiana’s Native Orchids, Magnificent Trees of Indiana, Be Tick Aware and much more.
The Indiana Forestry & Woodland Owners Association (IFWOA) was founded in 1977 and is a non-profit organization dedicated to conservation and sustainable management of woodlands in Indiana. IFWOA advocates for scientific best practices for management to achieve objectives of clean water, wildlife habitat, soil protection, native species diversity, timber production, recreation, carbon sequestration and many others.
IFWOA is an affiliate of the National Woodland Owners Association. IFWOA is a partner, collaborator or is represented on leading National and State organizations. These memberships or collaborations are selected to advance Indiana Woodland owner’s interests. IFWOA monitors and influences legislation and economic trends impacting Indiana woodlands and landowners for our members. Membership in IFWOA provides a valuable network linkage to information and resources at the leading edge of science, industry and politics impacting Indiana woodlands.
Resources:
Orchids of Indiana, Google Books
Wildflowers and Ferns of Indiana Forests: A Field Guide, Google Books
Wildflowers of the Midwest, Google Books
Magnificent Trees of Indiana, Purdue University Press
Forest Improvement Handbook, The Education Store, Purdue Extension’s resource center
Planting Hardwood Seedlings – The Education Store
Ordering Seedlings from the State Forest Nursery System, Got Nature? – Purdue Extension-FNR
Importance of Hardwood Tree Planting – The Education Store, Purdue Extension Resource Center
Forest Improvement Handbook – The Education Store
Designing Hardwood Tree Plantings for Wildlife – The Education Store
ID That Tree – YouTube Playlist
Forest Management for Reptiles and Amphibians: A Technical Guide for the Midwest, The Education Store
Hardwood Ecosystem Experiment – Forest Birds , Purdue Extension – FNR YouTube Channel
Managing Woodlands for Birds , Purdue Extension – FNR YouTube Channel
Sustaining Our Oak-Hickory Forests , Purdue Extension – FNR YouTube Channel
Ask the Expert: Hardwood Ecosystem Experiment – Birds and Salamander Research, Purdue Extension – FNR
Subscribe to Purdue Extension-FNR YouTube Channel
Liz Jackson, Engagement Lead
Indiana Forestry & Woodland Association
In this episode of ID That Tree, Purdue Extension forester Lenny Farlee introduces the Balsam Poplar. This species is found in the North Woods of Northern Wisconsin and the Upper Peninsula of Michigan. This species can be quite tall and has gray bark with relatively prominent diamond shapes along it. These trees have a very vertical form and their leaves are elongated, sharply pointed, and have a shiny finish. Balsam Poplar also have very resinous sticky bud scales located below the leaves along the stem.
If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.
Resources:
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Invasive Species Playlist, Playlist, Purdue Extension – FNR YouTube Channel (Asian Bush Honeysuckle, Burning Bush, Callery Pear, Multiflora rose)
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
How long do seeds of the invasive tree, Ailanthus altissima remain viable? (Invasive Tree of Heaven), USDA Forest Service
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Episode 11 – Exploring the challenges of Invasive Species, Habitat University-Natural Resource University
What are invasive species and why should I care?, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store, Purdue Extension Resource Center
Native Trees of the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources