Agroforestry VOLUME 26 I S SUE 1

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SO MANY TREES

to Choose From

Apopular catch-phrase in agroforestry circles is “the 

right tree in the right place for the right reason.” 

The words are simple enough, but implementation 

is much more complicated and difficult to achieve. 

The process of selecting the right trees and shrubs for an 

agroforestry system begins with the producer’s goals. Are 

they focused on production, some function such as water 

quality, habitat, or modifying wind speeds, or a combination 

of several goals? What species and varieties can meet those 

goals? “I want to grow chestnuts or elderberries because 

I think there is a good market for them,” is just the beginning. 

It is also necessary to determine if that species or a variety 

will not just grow, but thrive on the site you have chosen. 

There is more to it than simply comparing plant hardiness 

zones. Varieties and hybrids vary in production as well as in the 

soils, slopes and even altitude required for optimal growth.

Once the species and varieties are narrowed down the 

hunt begins. Are they available as bare root or potted 

plants? Can you buy them in bulk? Maybe you need to 

buy scion wood to graft to your root stock. Or maybe you 

will choose to collect seed and go into production.

The following articles highlight some of these 

questions as well as potential solutions for establishing 

a productive agroforestry enterprise.
2 Inside Agroforestry ] Volume 26, Issue 1

NAC Director's Corner

A commentary on the status of agroforestry by Susan Stein, NAC Director

This issue of Inside Agroforestry highlights a 

variety of considerations for identifying 

and acquiring productive plants to achieve 

producer goals. We hope that this opens 

the door a bit wider to the types of tools 

and information resources available. As you take the plant 

selection journey, please know that there are many resources 

available at USDA. I have featured a few here: 

• The Natural Resources Conservation Service (NRCS) 

has twenty-five Plant Materials Centers (PMCs), each 

based in ecologically distinct areas. The role of PMCs is to 

evaluate plants and vegetative technologies that support 

USDA conservation programs and practices. https://bit.ly/

NRCSPMC

• The USDA Forest Service Reforestation, Nurseries and 

Genetic Resources (RNGR) program mission is “To supply 

people who grow forest and conservation seedlings with 

the very latest technical information”. The RNGR website 

includes publications, a national nursery and seed directory, 

and a listing of events around the country associated with 

reforestation, native plant production, restoration, seeds etc. 

https://rngr.net

• The NRCS PLANTS Database includes standardized 

information about plants and lichens of the U.S. and 

its territories. It also provides plant symbols, checklists, 

distributional data, species abstracts, characteristics, images, 

crop information, automated tools, and references. 

https://plants.usda.gov/java/

• Lastly, the USDA Agricultural Marketing Service manages 

programs that support the production and availability of 

local and regionally-important plants. These programs 

include the Federal-State Marketing Improvement Program 

(FSMIP), Local Food Promotion Program (LFPP), Farmers 

Market Promotion Program (FMPP), and Specialty Crop 

Block Grant Program (SCBGP). Some of these programs are 

managed through State Departments of Agriculture. 

https://www.ams.usda.gov/services/grants 

We hope that these resources, as well as other ones 

presented in this issue of Inside Agroforestry, will help 

in your efforts to establish agroforestry systems with 

“the right tree, in the right place, for the right reason”. 

Please enjoy this edition of Inside Agroforestry.

Sincerely,

Susan Stein

NAC’s Website 

Has Moved!

You may notice that your old NAC links or bookmarks are not working, NAC's website has 

moved. The web site itself has not changed. However, 

if you have created bookmarks or posted NAC links on 

your website for specific pages or publications, they will 

not automatically redirect to the corresponding page at 

the new location. You will have to manually save or post new addresses for future use. 

We apologize for the extra work for you and your web managers. Questions or concerns about website changes can be addressed to Joe 

Banegas at: josephpbanegas@fs.fed.us. Thank you for your continued interest in agroforestry and NAC!

The USDA National Agroforestry Center’s 

website has moved to a new address:

www.fs.usda.gov/nac
Inside Agroforestry ] Volume 26, Issue 1 3

Agroforestry: Enhancing Resiliency 

in U.S. Agricultural Landscapes 

Under Changing Conditions

The USDA Forest Service recently released a report, Agroforestry: 

Enhancing Resiliency in U.S. Agricultural Landscapes Under 

Changing Conditions. This technical report presents the first-ever 

synthesis on agroforestry as a mechanism to provide mitigation 

and adaptation services in response to a changing climate. With 

contributions from more than 50 experts from the U.S., Canada, 

and Mexico, this report draws upon recent science and shows 

how tree-based management strategies can improve agricultural 

production and resiliency. The report can be downloaded at: 

https://www.fs.usda.gov/nac/publications/changing-conditions.

shtml. To request printed copies, please contact gbentrup@fs.fed.us. 

Selecting Plants for Adaptability

Richard Straight, National Agroforestry Center 

When selecting a tree or shrub for your farm, the most significant and commonly considered factor apart 

from soils, is local climate. Cold is an important concern. 

When it comes to plants, cold kills quickly. Choosing welladapted plants is even more crucial where production and 

income are concerned. Hence, it is important to consider the 

trends in changing climate patterns and weather variability.

Not surprisingly most people turn to the USDA Plant Hardiness 

Zone map. The map is based on the average annual minimum 

winter temperature, divided into 10-degree-Fahrenheit zones. 

However, there is more to determining plant suitability than cold 

hardiness (the lowest temperature that the plant can endure). 

The American Horticultural Society’s Plant Heat Zone Map 

measures the other extreme: heat tolerance. The zones indicate 

the average number of days each year that a given region in the 

United States exceeds 86 degrees. That is the temperature at which 

many plants begin suffering physiological damage from heat. 

The length of the growing season and number of frost-free days 

are also important. These factors are key to anticipating both 

the risk of frost damage when buds begin to break or grow 

as well as the timing of plant senescence (when it shuts down 

for the winter). In addition, the length of the growing season 

impacts plant growth and fruit maturation. For known cultivars 

and varieties, suppliers often provide information on length 

of growing season required. However, these details are often 

not know for plants from unknown sources or native plants.

When moving native plants or plants of unknown seed source 

across the landscape, such as from one woodland to another, 

two other factors come into play: latitude and altitude. 

These affect the length of growing season. Plants adapted to 

conditions further north and higher in altitude will also be 

adapted for shorter growing seasons. Rough rules of thumb are 

“don’t move a plant more than 75-100 miles north or south” 

and “don’t move it more than 1,000 feet in elevation.”

The tools and guidelines discussed here may be helpful 

in selecting adaptable species, cultivars and varieties 

for agroforestry production. Even so, remember 

the basics of soils, slope and precipitation! 

This map is NOT the official Plant Hardiness Zone Map. 

Please go to planthardiness.ars.usda.gov for the official map.

Reproduced with permission of the American Horticultural Society (www.ahsgardening.org)
4 Inside Agroforestry ] Volume 26, Issue 1

Chestnut Genetics for Your Farm

Casey Dahl, Folk Tree Farm

Kate MacFarland, USDA National Agroforestry Center

For many people this is the beginning of their journey into agroforestry. For other people it is 

the end, and not always a good place to end up. 

Why we plant trees is as important as what we plant. 

The two are linked because our motivations, goals, and 

expectations will help to determine the species and specific 

genetics needed. If we have goals that only specific species 

or genetics can accomplish, we will never fulfill those 

goals if we don’t choose our plant materials correctly. 

Many people are excited to incorporate chestnuts into a 

wide range of agroforestry systems. Chestnuts can serve 

as a good example for thinking about this plant material 

selection process. Which chestnuts should you plant? Which 

species and cultivars fit your needs? How do you decide?

The lack of information about nut tree cultivars in eastern 

North America makes gathering information even more 

important. Rather than consider “what variety is best?”, 

consider “what is best for me?” Some information on 

chestnuts is available through university publications, nonprofit organizations, government offices, and other sources. 

Learning from other growers about their experiences is also 

very helpful in answering the question “what is best for me?”

“I want to plant trees!”

What to consider before planting

 Cold hardiness

 Blight resistance

 Tree size

 Nut size

 How easily nuts peel

 Graft compatibility
Inside Agroforestry ] Volume 26, Issue 1 5

The following species may be options:

• Castanea dentata (American chestnut)

• Castanea sativa (European chestnut)

• Castanea crenata (Japanese chestnut)

• Castanea mollissima (Chinese chestnut) 

There are also a wide variety of crosses and cultivars among 

these species. So, how do you choose? Characteristics to consider 

include cold hardiness, blight resistance, tree size, nut size, ease of 

peeling nuts, and graft compatibility. Other factors are similar to 

what growers examine for all fruit and nut trees: pest and disease 

issues, fruit or nut yield, and market preferences or requirements. 

Personal goals are important as well. For example, while many 

producers choose not to plant American chestnuts because of 

their blight susceptibility and small nut size, others may want 

to preserve their genetics, to trial trees from breeding programs 

aimed at adding blight resistance to American chestnuts, or 

because they live in an area of the country where there is not 

blight. Producers are making a wide range of choices based on 

individual situations – there is no one-size-fits-all solution. 

Producers have several options on planting chestnuts, as 

seedlings or as grafted plants. Each has its advantages and 

disadvantages. With grafted cultivars, you are more likely 

to get uniform yield, performance, disease resistance, and 

ripening time as well as shorter timeline to production. But, 

grafted trees cost more (in either money or time, if you choose 

to grow seedlings and graft your own), can be affected by 

graft incompatibility, and sometimes result in lower vigor, 

especially in the north. Seedlings are cheaper, more vigorous, 

and face no danger of graft failure. However they may have 

poor production (size or quality of nut) and different ripening 

times. In addition, disease resistance and cold hardiness is 

uncertain. Seedlings from cultivars have an advantage over 

generic seedlings - because you know that at least one parent 

has good characteristics. In addition, grafting a cultivar to its 

seedling may increase the success of grafts. Some orchards are 

relying entirely on seedling chestnuts and doing quite well. 

In the end, consider what you want to achieve with each 

particular component of an agroforestry system as you 

assess plant materials for inclusion. Reach out to producers, 

universities, technical assistance providers, and others in the 

agroforestry community to share and learn. If you do your 

homework first, you can find nurseries that grow what you 

need. This will lead to a much better outcome than relying 

only on what a particular nursery may have in stock. 

For more information on selecting chestnut genetics for your 

agroforestry system, watch the “Nutshell” presentation, hosted 

by the Savanna Institute: https://youtu.be/_9xnZL2myMI

Seedlings vs. Grafting

 Cheaper

 More vigorous

 No danger of graft failure

 Possible lower quality

 Possible smaller nut

 Unknown disease resistance 

& cold resistance

 Uniform yield

 Performance

 Disease resistance

 Quicker timeline 

to production

 Potential graft incompatibility

 Increased cost

 Possible lower vigor
6 Inside Agroforestry ] Volume 26, Issue 1

New Treat or New Threat? 

Deciding if a New Crop is a Risk

Richard Straight, USDA National Agroforestry Center

Diversifying crops to take advantage of a broader market and to hedge against risk is a proven strategy. One timeproven way to diversify crops is to find non-native plants that 

bear edible fruits, nuts, roots or leaves or even unique flowers and 

stems for crafts or decorative uses. Some introduced fruits have 

become so common that it is easy to forget their origins; apples, 

pears, cherries, citrus, plums, figs, strawberries and grapes are 

just a few non-native species that have become commonplace.

However, there is a risk associated with planting an 

unfamiliar non-native plant. Will it become invasive and a 

future management problem? Predicting the future is always 

difficult, especially when it comes to living systems. A safe 

and conservative approach is to cultivate only native plants.

Can we take advantage of what have we learned about invasive 

plants? Can we make an educated evaluation of the potential 

for an introduced plant to be invasive or become a weed? One 

useful tool developed for Hawaii and other Pacific Islands 

is the Hawai’i Pacific Weed Risk Assessment, HPWRA, 

https://sites.google.com/site/weedriskassessment/home. This 

is a screening tool to ask “background questions” about a 

plant before it is imported or widely planted in Hawai‘i.

The HPWRA is a Free Service.

More than 1900 plants have been screened to date. The updated 

list of completed assessments is available as a spreadsheet or pdf. 

If the plant in question is not on the list it can be submitted for 

screening via email to the HPWRA screener at hpwra@yahoo.com. 

How does the HPWRA Work?

No one is required to use the HPWRA. When requested, 

botanists review available information to answer 49 questions 

about a plant’s biology, ecology and invasive tendencies in other 

settings. The answers result in a score that predicts whether a 

plant is likely to be invasive in Hawai‘i or other tropical Pacific 

islands sharing a similar climate.

Is the HPWRA a Good Predictor?

During the testing process the tool was found to be 95% accurate 

in catching the would-be invasive plants and 85% accurate at 

identifying non-pests.

What Other Tools are Available?

Other tools have been developed to help identify potentially 

invasive plants and other organisms. Some of these tools are 

regionally-focused. The Invasive Species Assessment Protocol 

was developed in 2004 through a partnership of the NatureServe, 

The Nature Conservancy and the U.S. National Park Service. 

This tool assesses, categorizes, and lists non-native invasive 

plants according to their impact on native species and natural 

biodiversity in a large geographical area such as a nation, state, 

province, or ecological region.

The protocol is offered in generalized form for others who might 

wish to use it to conduct similar assessments and create lists of 

invasive plants for other nations, states, provinces, ecological 

regions, or comparable areas, http://www.natureserve.org/

biodiversity-science/publications/invasive-species-assessmentprotocol-evaluating-non-native-plants. NatureServe is now 

using this protocol outside of the United States to assess the 

biodiversity impact of the approximately 3,500 non-native 

vascular plant species. 

During the testing process of the 

HPWRA tool it was found to be:

95%

accurate 

in catching the wouldbe invasive plants and

85%

accurate 

at identifying

non-pests.
Inside Agroforestry ] Volume 26, Issue 1 7

Southwest Plant Selection Tool 

Adapted from NRCS - Plant Selection Tools for Revegetation Efforts in the Southwest

In California, the eVeg Guide is a tool developed by NRCS in partnership with Calflora. The search function for 

eVeg allows users to select plnat species for NRCS conservation practices and purposes based on the constaraints of 

elevation, climate, soil, and evapotranspiration zones. Plant choice may be made with either EPA Ecoregion or Calflora 

incidence data to ensure that only adapted plants will be chosen. Ther are also options to link to the NRCS PLANTS 

Database and Plant Guides to provide more information on each species. An instructional guide for eVeg is available 

on YouTube. (Adapted from NRCS - Plant Selection Tools for Revegetation Efforts in the Southwest.)

In Brief...

A periodic summary of agroforestry-related journal articles 

John S. Weedon, Stark (OH) Soil & Water Conservation District

Researchers recently compared seven hardwood species in an alley cropping 

system in southwest Quebec province over a five-year period. The species 

were Carya ovata (shagbark hickory), Juglans nigra (black walnut), Quercus 

bicolor (swamp white oak), Quercus macrocarpa (bur oak), Quercus rubra 

(red oak), Acer Saccharum (sugar maple), and four clones of hybrid poplars. 

The mean survival rate for the six hardwoods planted as 3-year-old 

bareroots was 70%, and the rate for hybrids 82% with no differences 

among the clones. Sugar maple (33%) and shagbark hickory (57%) 

had the lowest survival rates. The investigators also planted red oaks 

and sugar maples as 6-year-old root balled transplants. They had 

a 100% survival rate, which is consistent with other studies that 

indicate large-sized seedlings effectively improve tree survival.

Tree growth among the 3-year-old transplants ranged from 268 to 379 cm. 

Tree height of swamp white oak and bur oak was greater than shagbark 

hickory, black walnut, and red oak. Sugar maple height was intermediate. 

The 6-year-old transplants red oak and sugar maple grew higher than 

3-year-old transplants of the same species and the cost per dm3 of stem 

volume was lower. Height and DBH for the hybrids ranged widely.

Tree external defects were observed on 63% of the hardwood individuals. 

Black walnut, swamp white oak, and bur oak had more defects than 

shagbark hickory, red oak, and sugar maple. Defects were observed 

on 55% of the hybrid poplars with variations among the clones.

Take Home Message: Because survival, growth, and defects vary 

widely among hardwood species, hybrid poplars, and planting stock, 

substituting one species or stock for another in an alley cropping system 

may yield different outcomes. Producers need to choose wisely.

Rivest D, Cogliastro A. 2018. Establishment success of seven hardwoods 

in a tree-based intercropping system in southern Quebec, Canada. 

Agroforest Syst. https://doi.org/10.1007/s10457-018-0211-0.

Different species, different results Alley Cropping’s Favorite Playlist

In the past 35 years, agroforestry researchers have 

written 1,244 publications from 77 countries on 

alley cropping. On the one hand, 192 tree and 

181 crop genera were studied across three climate 

zones. On the other hand, most research was 

limited to a few genera and functionalities. In the 

temperate zone, the majority of the studies were 

on Populus and Juglans for trees and Zea, Glycine,

and Triticum for crops. In the subtropics, it was 

Eucalyptus and Populous for trees and Zea and

Triticum for crops. And in the tropics, most were 

devoted to Leucaena and Gliricidia for trees and 

Zea and Coffea for crops. Moreover, agricultural 

function was focused as well with 82% of the 

studies in the temperate zone studying trees only 

as biomass. Going forward, the paper’s authors 

recommend that researchers explore four rarely 

travelled topics: within system tree diversity; tree 

crops for food and fodder production; perennial 

alley crops; and trees for crop facilitation (via 

shade, nitrogen fixation, and mulch production).

Take Home Message: Most research on alley 

cropping has been limited to a handful of tree 

and crop genera and agricultural functions. 

Opportunities exist to broaden our knowledge 

of potential alley cropping systems.

Wolz KJ, DeLucia EH. 2018. Alley Cropping: 

Global patterns of species composition and 

function. Agr Ecosyst Environ. 252:61-68.
8 Inside Agroforestry ] Volume 26, Issue 1

Inside Agroforestry VOLUME 26, ISSUE 1

USDA National Agroforestry Center

1945 N 38th St.

Lincoln, NE 68583–0822

Official Business

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Address Service Requested

Upcoming Events

June 24-27, 2019

North American 

Agroforestry Conference

Corvallis, OR

September 22, 2018

Growing American Ginseng

Binghamton, NY

bit.ly/2Lsypaq

December 7-8 2018

Savanna Institute Perennial Farm Gathering

Madison, WI

http://www.savannainstitute.org/perennial-farm-gathering.html

For more upcoming events, visit our website calendar: www.fs.usda.gov/nac/events

“Inside Agroforestry” is published by the USDA National 

Agroforestry Center. 

Phone: 402-437-5178 

Fax: 402-437-5712

• Susan Stein, NAC Director

• Forest Service Research Lead - Vacant

• Richard Straight, FS Lead Agroforester (ext. 4024)

• Kate MacFarland, FS Assistant Agroforester (ext. 4012)

• Joseph Banegas, Information Assistant/ 

 “Inside Agroforestry” Designer (ext. 4014)

www.fs.usda.gov/nac

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The USDA National Agroforestry Center (NAC) is a partnership of the Forest Service (Research & Development and State & Private Forestry) 

and the Natural Resources Conservation Service. NAC’s staff is located at the University of Nebraska, Lincoln, NE. NAC’s purpose is to 

accelerate the development and application of agroforestry technologies to attain more economically, environmentally, and socially sustainable 

land use systems by working with a national network of partners and cooperators to conduct research, develop technologies and tools, establish 

demonstrations, and provide useful information to natural resource professionals.

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