United States

Department of 

Agriculture

Forest Service

Northern 

Research Station

General Technical

Report NRS-55

Kathleen S. Knight

Robert P. Karrfalt

Mary E. Mason

Methods for 

Collecting Ash 

(Fraxinus spp.) Seeds
Abstract

The threat of emerald ash borer (Agrilus planipennis) has necessitated ash 

seed collection to preserve the ash genetic resource. For ash species found 

only in natural areas, we have developed seed collection methods that 

require no special training or certifi cation. Collection techniques for natural 

areas include pole pruners for branches lower than 30 ft (9 m) and ropes or 

rope saws for higher branches. Seed collection must be timed correctly by 

examining samara color, seed coat color, and embryo size to be sure that 

seeds are fully mature. Documentation of seed identity and post-harvest 

handling of seeds are discussed.

The Authors

KATHLEEN S. KNIGHT, Research Ecologist, U.S. Forest Service, Northern 

Research Station, Delaware, OH.

ROBERT P. KARRFALT, Director, U.S. Forest Service, National Seed 

Laboratory, West Lafayette, IN.

MARY E. MASON, Research Associate, The Ohio State University, Ohio 

Agricultural Research and Development Center, Wooster OH, Department 

of Entomology.

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Manuscript received for publication 22 October 2009

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or the Forest Service of any product or service to the exclusion of others 

that may be suitable.
1

INTRODUCTION

Ash (Fraxinus) is an important genus in North America with 16 species 

spread across the continent (USDA NRCS 2009). A prolifi c and 

regular producer of seeds, it readily establishes naturally in disturbed 

areas within its range. For some conservation and timber purposes, 

white and green ash seeds were collected and occasionally seed orchards 

were planted in the past; however, to date there has been only a small 

need to collect ash seeds in the wild. But arrival and spread of the 

emerald ash borer (Agrilus planipennis) from Asia, which has already 

killed tens of millions of ash trees in the U.S. and Canada (EAB Info 

2009) and has the potential to devastate North American ash species 

(Cappaert et al. 2005), has created the need to preserve the ash genetic 

resource through long-term seed storage. Th e seeds may be used for 

future research or restoration. Th erefore, techniques for seed collection 

in natural areas are now needed.

SEED COLLECTION TIMING

Timing seed collection correctly is as important as having a good 

technique for gathering the seeds. Seeds should be collected when they 

are physiologically mature, at which point they have the greatest ability 

to survive in storage and produce a strong seedling. Physiological 

maturity is reached just before the seed is naturally shed from the 

tree. Seed maturity dates diff er among species, years, and locations. 

Ripening dates are listed in the Woody Plant Seed Manual for ash 

species that occur in regions currently infested by the emerald ash borer 

(Bonner and Karrfalt 2008) (Table 1). In Ohio, green ash samaras may 

Table 1.—Seed maturity dates of ash species

Common name Scientif c name Seed maturity date

White ash F. americana October-November

Green ash F. pennsylvanica September-October

Pumpkin ash F. profunda September-October

Black ash F nigra June-September

Blue ash F. quadrangulata June-October

Carolina ash F. caroliniana August-October
2

persist on the tree until December, blue ash samaras may fall by midSeptember, and pumpkin ash and black ash samaras may fall by midOctober (Knight and Mason, personal observation). Insect-damaged 

seeds, empty seeds, or storms can result in premature seed shed, which 

should not be confused with true mature seed shed.

Despite the published seed maturity dates, the best way to judge 

seed maturity is to dissect a few seeds. Botanically, the fruit of an ash 

is known as a samara, which contains a single ash seed. Th e samara 

changing color is the fi rst sign that the seed is maturing. Samaras 

change from green to pale green, yellow-green, tan, and fi nally dark 

brown. Molds can also darken and spot the outer layer of the samara 

until some appear almost black. Th is apparently is not harmful because 

such seeds are found to germinate.

In addition to observing the color change of the samara, it is necessary 

to observe the internal structures of the seed to decide if the seed is 

mature and healthy enough to collect. Th ere are three reasons for 

examining the internal structures. First, ash samaras may mature even if 

they do not have any true seeds inside. Secondly, insects can damage the 

seeds (Fig. 1). Finally, it is necessary to know that the seeds are mature. 

A seed can be removed from the samara to determine the color of the 

seed coat. Th e seeds are mature when the seed coat turns tan to dark 

brown (Fig. 2). Th e samara should also be cut lengthwise to expose the 

Figure 1.—Ash seeds damaged by insects are not viable. A weevil larva is inside 

the seed. 

Robert Karrfalt, U.S. Forest Service
3

embryo inside the seed. Th e 

seeds of white ash, green ash, 

pumpkin ash, and Carolina 

ash are mature when a fi rm, 

white embryo fi lls the seed 

cavity (Bonner and Karrfalt 

2008) (Fig. 3). Ripe seeds of 

blue ash (Mason, personal 

observation) and black ash 

(Bonner and Karrfalt 2008) 

have immature embryos that 

do not fi ll the seed cavity, so 

seed coat color and fi rmness 

of the embryo must be used to 

judge ripeness. Blue ash and 

black ash embryos will grow 

once dormancy is broken.

It is useful to scout potential 

seed collection areas 

beforehand to determine 

locations with enough healthy 

seeds to make collection 

worthwhile. Under normal 

circumstances, seeds should 

not be collected from trees 

where less than 80 percent of 

the seeds are good, particularly 

during a good seed year. 

However, if the trees will soon 

be lost to emerald ash borer, 

it may be necessary to collect 

from trees with somewhat 

poorer quality seeds. Mast 

seed crop years may occur 

Figure 2.—Blue ash samara pulled apart 

to expose seed. Seed removed (arrow). 

Seed coat is brown and ready for harvest.

Figure 3.—Green ash seeds cut 

lengthwise. Immature seed has placental 

tissue (arrow) taking up the right and lower 

portions of the seed, unf lled cavity (arrow) 

at the top and bottom, and the developing 

embryo (arrow) only f lling a portion of the 

seed. Mature seed has a f rm, full length 

embryo f lling entire seed (arrow).

Kathleen Knight, U.S. Forest Service.

Seed



Robert Karrfalt, U.S. Forest Service.



Unfi lled 

cavity

Developing 

embryo

Placental Placental 

tissue





Embryo 

cotyledons cotyledons Embryo 

radicle

Full length embryo Full length embryo 

fills seed cavity

 




4

every 1 to 5 years, depending on the ash species (Bonner and Karrfalt 

2008), but in some non-mast years there may be few seeds produced 

(Knight, personal observation). Scouting also makes it easier to plan 

the distribution of samples across a location and determine which seed 

collection techniques will be needed.

SEED COLLECTION TECHNIQUES

Seeds of common ash species can be easily collected along roadsides, 

because open-grown ash trees can produce seeds throughout the crown, 

providing copious amounts of seeds that are easy to reach. Less common 

ash species may be found primarily in forested natural areas. In these 

areas, the lowest branches with samaras may be 6 to 24 m (20 to 80 ft) 

above the ground, making seed collection challenging. Tree climbing has 

frequently been used in the past to collect seeds from tall trees of other 

species, especially conifers. Th at method, however, requires specialized 

training and equipment to be carried out safely. Th ree productive and 

economical methods for collecting seeds in forested areas allow the 

worker to remain on the ground: pole pruners, rope, and rope saw. Using 

a shotgun to shoot down small branches with seeds and cutting down the 

entire tree are also appropriate methods in certain circumstances, but are 

not discussed here.

Pole Pruners

Pole pruners consist of pole sections and a cutting head with a long rope 

attached. Pole pruners are most useful for collecting seeds less than 9 m 

(30 ft) above the ground, and will cut a branch up to 4 cm (1.5 in.) in 

diameter (check individual pruner specifi cations). First, a tarp is spread 

on the ground beneath the lowest small diameter branch with samaras. 

Pole sections are added until the desired height is attained, the cutting 

head is hooked over the branch, and the rope is used to operate the 

cutting head to cut the branch (Fig. 4).

Pole sections can be made from fi berglass, aluminum, or wood, and a 

variety of cutting heads are available. Th e taller the pole pruner is, the 

more diffi cult it is to control from the ground, and the more upper body 
5

strength is required to lift the pole to add new sections. It is helpful to 

wrap the rope around long, fl exible poles to prevent them from bending 

when the rope is pulled to operate the cutting head. A lightweight 

cutting head and lightweight rope will help prevent the long poles from 

bending over. Resting the pole on a cross branch can support the pole 

while sections are added or steady the pole if it starts to sway. Care 

should be taken to keep the rope clear of small side branches. Most 

cutting heads have a lever action so the pruner head should be positioned 

to allow suffi cient clearance (e.g., on the outside of a fork). For more 

leverage, one person can steady the pole and a second can operate the 

rope, or the butt of the pole can also be braced against the ground and 

Figure 4.—Ian Chambers (Ohio 

State University) uses pole 

pruners to collect pumpkin ash 

seeds at Maumee Bay State Park.

Kathleen Knight, U.S. Forest Service
6

boot instep to free both hands for pulling on the rope. Th e pole will 

be unsupported once the branch is cut and may start to fall, especially 

if the pole is angled during cutting. Bracing the bottom of the pole 

against the instep and keeping tension on the rope can slow the pole’s fall 

and prevent damage. Cut branches often fall straight down toward the 

operator, especially when the pole must be kept nearly vertical to keep it 

from falling while cutting higher branches. Many poles have a hook for 

positioning, and the hook can be used to pull down branches that hang 

up after cutting.

Another way to use the pole pruner is to put a hook on the pole to 

allow the cut end of the branch to be lowered gently (Fig. 5). A simple 

hook can be made from fl exible 3/8 in. water pipe. Th e hook is slid 

into the crotch of the branch and a lateral branch. Th e cutting head is 

then placed over the branch and the cut is made. Th e cut end of the 

branch is caught on the hook and can be lowered to the ground without 

shattering the seeds into the undergrowth. If the pole is not too long and 

Figure 5.—An ash branch, laden 

with ash seed, is gently lowered 

to the tarp using modif ed pole 

pruners (arrow).

Robert Karrfalt, U.S. Forest Service

Lateral 

branch
7

there is enough clear area, the pole can be simply swung to the ground. 

Otherwise, sections need to be taken off the pole in order to lower the 

cut branch. Th is technique can be used without the tarp, which is a good 

alternative where it is not possible to spread the tarp on the ground (e.g., 

areas with dense understory shrubs or ash branches above rivers or lakes).

Safety is important for all methods of ash seed collection. Pole pruners 

should never be used near power lines due to the risk of electrocution. 

Pole pruners operated very high have the potential to fall. Cut branches 

may fall directly toward the operator. Communication between the 

operator and the rest of the crew is important. Everyone on the crew 

should wear hard hats and eye protection and watch out for falling 

branches or equipment.

Rope

Th is method uses a strong rope over a branch to allow the seed collector 

to shake the branch so that samaras fall onto a large tarp on the ground, 

to bend the branch down so that the pole pruners can reach it, or to 

break the branch. First, a tarp is spread on the ground beneath the target 

branch with samaras. Th en, a 340- to 450-g (12- to 16-oz.) throw bag 

with a lightweight throw line is thrown or shot over the target branch 

(Fig. 6). We have successfully used the Big Shot® slingshot from Sherrill 

Tree to shoot a 400-g (14-oz.) throw bag over branches 24 m (80 ft.) 

above the ground. Th e throw line is spooled into a bag or box so that it 

does not tangle, and the bottom end is attached to a heavier strong rope, 

which is spooled into its own bag so that it does not tangle. Once the 

throw line is over the target branch (binoculars are useful to determine 

this), the throw line is used to pull up the heavier rope (Fig. 7). Once the 

heavier rope is over the branch, the branch can be shaken or pulled down 

to remove seeds (Figs. 8 and 9).

In our experience, black ash branches are easiest to break, while pumpkin 

ash, blue ash, and green ash branches are very fl exible and more diffi cult 

to break. Working with high branches on a windy day makes it diffi cult 

to get the samaras to land on the tarp if the shaking method is used. If 
8

Figure 6.—Tim Fox (U.S. Forest 

Service) uses the Big Shot® sling shot 

(arrow) to shoot a throw bag (arrow) 

over a black ash tree branch at Fowler 

Woods State Nature Preserve. 

Resources (ODNR)Photo used with permission by Tom Arbour, Ohio Department of Natural 

Figure 7.—Tim Fox (U.S. Forest 

Service) uses the red throw line 

(arrow) to pull up the heavier white 

rope (arrow). The red throw line is 

spooled into the paper bag.

Photo used with permission by Tom Arbour, ODNR

Tarp

→

Heavier 

white rope

→

Red throw 

line

→

Throw bag 

in pouch

→

→

Sling shot

Figure 8.—Tim Fox (U.S. Forest 

Service) uses the heavier rope to 

shake a black ash tree branch (left).

Figure 9.—Pumpkin ash samaras 

fall on the tarp as a branch is 

shaken.

Photo used with permission by Tom Arbour, ODNRKathleen Knight, U.S. Forest Service
9

the wind is consistent, it may be possible to gently shake the branch so 

that a few samaras fall to determine where they will land, then set up the 

tarp in that area. Breaking off a small branch laden with samaras so that 

it falls on the tarp is often the most effi cient method of seed collection.

Safety is important for all methods of ash seed collection. Rope should 

never be used to collect seeds from branches near power lines due to 

the risk of electrocution. A 400-g (14-oz) throw bag shot 24 m (80 ft) 

into the air will hit the ground with a velocity of 22 m/s (49 mph). It is 

best to shoot the sling shot at a slight angle, rather than straight up, and 

make sure no one is standing in the direction of its trajectory. Broken 

branches may fall directly toward the operator. Communication between 

the operator and the rest of the crew is important. Everyone on the crew 

should wear hard hats and eye protection and watch out for falling throw 

bags and branches.

Rope Saw

In this method, a strong rope is used to 

maneuver a rope saw into position on 

the branch and then to cut the branch. 

Th is method works best for branches at 

least 2 cm (3/4 in.) in diameter. First, 

a tarp is spread on the ground beneath 

the target branch with seeds. Th en, a 

throw bag with throw line is thrown or 

shot over the target branch, preferably 

positioned so the rope is only over the 

target branch. Rope is attached to both 

sides of the rope saw, with one end 

attached to the throw line, which is used 

to pull the rope saw into the tree. When 

the rope saw is oriented over the branch 

to be cut, the ropes are used to move 

the rope saw back and forth to cut the 

branch (Fig. 10).

Figure 10.—Tim Fox (U.S. Forest 

Service) operates a rope saw to 

cut a branch from a blue ash tree 

at Sharon Woods MetroPark.

Kathleen Knight, U.S. Forest Service
10

Because some ash trees have fl exible limbs, it is necessary to cut larger 

branches on these trees. One or two people can operate the saw (one as in 

Fig. 10, or two people on opposite sides of the branch). Standing to the 

side so the rope is at an angle (as in Fig. 10) allows the operator to cut the 

top, opposite side, and bottom of the branch, which may prevent bark 

tearing and branch hangups. Steeply angled branches should be avoided 

because the saw will slide down the branch. Sharp crotches should also be 

avoided because the saw or knots can become stuck in them.

Several diff erent saws, varying in number of teeth, thickness, and other 

features, are available from diff erent manufacturers. In our experience, 

the Pocket Chainsaw® manufactured by Supreme Products cuts quickly 

and readily orients with the cutting teeth toward the branch. We created 

larger attachment loops using 12 gauge high tensile wire and connectors 

(Fig. 11). Th e use of two diff erent colors of brightly colored rope, one for 

each side of the saw, increases visibility of the line and saw position.

Safety is important for all methods of ash seed collection. A rope saw 

should never be used to collect seeds from branches near power lines due 

to the risk of electrocution. Cut branches may fall directly toward the 

operator. Pulling hard on a stuck saw may cause it to quickly fl y toward 

Figure 11.—Rope saw with custom attachment loops and 

440 lb (200 kg) paracord.

Mary Mason, Ohio State University
11

the operator. Communication between the operator and the rest of the 

crew is important. Everyone on the crew should wear hard hats and eye 

protection and watch out for falling equipment and branches.

POST-HARVEST SEED HANDLING

Proper handling of the seeds after harvest is important to preserve 

the identity, viability and vigor of the seeds. Each collection must be 

properly documented by recording the location of the mother tree, 

species, collection date, and name of the seed collector(s). Additionally, 

a voucher specimen should be taken from each tree and pressed (Fig. 

12). Ash species readily hybridize, and vouchers are important tools for 

verifying species identity. Ideally, the voucher specimen should consist of 

an older portion of the twig with leaf scars, a new twig with the terminal 

bud, a leaf, and a full cluster of samaras. A photo of the bark and a photo 

of the whole tree or the stand in which it was found are also helpful for 

species verifi cation. Leaf and full fruit clusters may be diffi cult to obtain 

late in the collection season as leaves fall and seeds disperse.

Figure 12.—Voucher specimen of white ash.

Kathleen Knight, U.S. Forest Service
12

Seeds should be placed in paper bags and, ideally, kept separate by 

mother tree. Keeping the seeds separate by mother tree provides more 

options for using the seeds in the future and gives the opportunity to 

verify species identity at a later time. If possible, separate collections 

by mother tree should be made because these are of greater value in 

breeding work and genetic studies and will greatly facilitate restoration 

work. In extreme circumstances, such as low seed yields, loss of seeds, 

and loss of documentation, it may be necessary to bulk seed collections 

by stand, but this is not the preferred option. Seeds should not be 

exposed to high temperatures, e.g., leaving them in a hot car in the sun, 

because this can reduce the viability of the seeds. Seeds should be kept in 

paper bags at room temperature until shipped to a seed storage facility 

along with documentation, vouchers, and photos, as soon as possible 

after collection.

After ash seeds are received at the National Seed Lab, protocols are 

followed to eliminate weevils and damaged or unfi lled seeds and to 

prepare the seeds for long-term storage. Weevils (Th ysanocnemis bischoffi , 

T. helvola, and T. horridulus) attack ash seeds (Barger and Davidson 

1967, Solomon et al. 1993) and the larvae are usually in the seeds at 

harvest. If seeds are immediately dried following harvest, weevils will 

die and permanently remain in the seeds. Keeping the seeds below 

21°C (70°F) after collection without drying and then placing them in 

a cold room at about 3°C for 2 to 4 weeks will cause the weevil larvae 

to leave the seeds in an attempt to go into the earth to pupate (Karrfalt, 

personal observation). After weevils are eliminated, the infested seeds 

are much lighter and can subsequently be more easily removed from the 

seed lot with a seed aspirator to improve the germination percentage. 

Next, the seeds should be equilibrated at about 30 percent relative 

humidity, rubbed free from the stems, aspirated, sealed in a moistureproof container such as a heavy 6-mil poly bag to maintain low moisture 

content, and frozen at or below -8 °C (18 °F). It is expected that the 

ash seeds will remain viable for at least several decades for use in future 

research, breeding, or restoration work.
13

RESOURCES

Other resources are available from the National Seed Lab ash seed 

collection Web site: www.nsl.fs.fed.us/GeneticConservation_Ash.html.

• Th e rope technique for ash seed collection in natural areas – 

video by Kathleen Knight

• National Seed Lab protocol for ash seed collection – 

Powerpoint and Webinar by Robert Karrfalt

To participate in the U.S. Forest Service ash seed collection eff ort, 

contact:

Robert P. Karrfalt - Director, National Seed Laboratory

rkarrfalt@fs.fed.us 478-751-4134

LITERATURE CITED

Barger, J.H.; Davidson, R.H. 1967. A life history of the ash seed 

weevils, Th ysanocnemis bischoffi Blatchley and T. helvola Leconte.

Ohio Journal of Science. 67(2): 123-127.

Bonner, F.T.; Karrfalt, R.P., eds. 2008. Th e woody plant seed manual.

Agric. Handbk. No. 727. Washington, DC: U.S. Department of 

Agriculture, Forest Service. 1,223 p. (http://www.nsl.fs.fed.us)

Cappaert, D.; McCullough, D.G.; Poland, T.M.; Siegert, N.W. 

2005. Emerald ash borer in North America: a research and 

regulatory challenge. American Entomologist. 51(3): 152-165.

[EABInfo] Emerald Ash Borer Information. 2009. Emerald ash borer 

information. (http://www.emeraldashborer.info/index.cfm)

Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, R.L.; 

Th ompson, L.C.; McCracken, F.I. 1993. Ash pests: a guide to 

major insects, diseases, air pollution injury, and chemical injury.

Gen. Tech. Rep. SO-96. New Orleans, LA: U.S. Department of 

Agriculture, Forest Service, Southern Forest Experiment Station. 45 p.
14

U.S. Department of Agriculture. Natural Resources Conservation 

Service. 2009. Th e PLANTS Database (http://plants.usda.gov) 

(12 August 2009). National Plant Data Center, Baton Rouge.

ACKNOWLEDGMENTS

We thank Tim Fox and Ian Chambers for their help in developing 

these techniques during seed collection in fall 2008. We thank Les 

Benedict for advice on ash seed collection. Tom Arbour photographed 

the rope technique. Th e Ohio DNR Division of Natural Areas and 

Preserves, Columbus MetroParks, and Maumee Bay State Park allowed 

us to collect seeds. Paul Berrang and Andrew David provided helpful 

reviews that greatly improved this report.
Knight, Kathleen S.; Karrfalt, Robert P.; Mason, Mary E. 2010. 

Methods for collecting ash (Fraxinus spp.) seeds. Gen. 

Tech. Rep. NRS-55. Newtown Square, PA: U.S. Department of 

Agriculture, Forest Service, Northern Research Station. 14 p.

The threat of emerald ash borer (Agrilus planipennis) has 

necessitated ash seed collection to preserve the ash genetic 

resource. For ash species found only in natural areas, we have 

developed seed collection methods that require no special training 

or certification. Collection techniques for natural areas include pole 

pruners for branches lower than 30 ft (9 m) and ropes or rope saws 

for higher branches. Seed collection must be timed correctly by 

examining samara color, seed coat color, and embryo size to be sure 

that seeds are fully mature. Documentation of seed identity and postharvest handling of seeds are discussed.

KEY WORDS: Fraxinus, ash, seed, samara, collection

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