26
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004 723

Chapter 26 Seed Germination
Table 1—Mean germination energy and mean germination capacity of 18 grass, 27 forb, and 28 shrub species following specified number of days. Germinated in the dark at 34 to 38
∞
F (1.1 to 3.3
∞
C).
Species
Germinative energy a
Percent Days
Germinative capacity
Percent b
Days
Number of accessions c
Grasses
Bluegrass, Kentucky
Brome, mountain
Brome, meadow, ‘Regar’
Brome, smooth southern
Fescue, hard sheep
Foxtail, meadow
Orchardgrass
Orchardgrass, ‘Paiute’
Rye, mountain
Squirreltail, bottlebrush
Wheatgrass, bluebunch
Wheatgrass, standard crested
Wheatgrass, fairway crested
‘Ephraim’
Wheatgrass, intermediate
Wheatgrass, pubescent ‘Luna’
Wheatgrass, tall
Wildrye, Great Basin ‘Magnar’
Wildrye, Russian
Forbs
Alfalfa ‘Ladak’
Alfalfa ‘Nomad’
Aster, Pacific
Aster, Engelmann
Aster, blueleaf
Balsamroot, arrowleaf
Balsamroot, cutleaf
Burnet, small
Clover, strawberry
Cowparsnip
Crownvetch
Flax, Lewis ‘Appar’
Geranium, Richardson
Goldeneye, showy
Helianthella, oneflower
Lomatium, narrowleaf
Lupine, mountain
Lupine, silky
Milkvetch, cicer
Penstemon, low
Penstemon, Palmer ‘Cedar’
Sainfoin
Salsify, vegetable oyster
Sweetanise
Sweetvetch, Utah (shelled)
Sweetvetch, Utah (unshelled)
Sweetclover, yellow
Shrubs
Apache plume
Bitterbrush, antelope
Bitterbrush, desert
Ceanothus, Martin e
Chokecherry, black
27
54
90
67
58
75
70
30
45
75
85
78
90
70
70
75
53
70
85
56
34
80
26
26
17
80
56
30
35
70
16
20
50
49
63
73
20
21
62
80
48
34
40
28
75
23
72
58
33
32
70
38
28
21
30
30
28
56
30
28
21
30
28
28
28
30
50
28
14
14
120
150
90
98
98
21
60
150
45
45
180
150
90
130
36
56
75
150
49
21
35
180
50
50
14
60
42
28
120
150
30
77
92
80
82
80
91
72
49
95
93
88
92
93
93
90
75
91
92(3) d
94(3) d
59
83
48
40
35
91
91
64
55(20) d
80
22
27
90
72
77
95
32(65) d
42
86
91
63
60
63
34
90
63
90
86
38
72
365
120
42
49
60
75
45
112
60
49
45
80
42
50
50
120
250
49
28
45
180
180
180
175
180
35
365
365
180
75
365
365
180
365
98
98
150
365
63
35
130
365
200
210
42
180
56
70
240
365
16
5
8
8
8
30
12
12
8
7
6
7
6
24
10
10
18
12
8
40
12
8
8
10
10
8
8
16
10
18
4
20
10
22
10
8
4
7
12
22
4
6
4
12
10
16
30
16
8
4
(con.)
724 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004

Chapter 26 Seed Germination
Table 1 (Con.)
Species
Germinative energy a
Percent Days
Germinative capacity b
Percent Days
Number of accessions c
Shrubs
Cliffrose
Currant, golden
Ephedra, green
Ephedra, Nevada
Greasewood, black e
Hopsage, spiny
Kochia, forage ‘Immigrant’
Mountain mahogany, curlleaf
Mountain mahogany, true
Peachbrush, desert
Rabbitbrush, mountain low
Rabbitbrush, mountain rubber
Rabbitbrush, whitestem rubber
Sagebrush, basin big
Sagebrush, black
Sagebrush, fringed
Sagebrush, mountain big
Sagebrush, Wyoming big
Saltbush, fourwing e
Saltbush, Gardner e
Serviceberry, Saskatoon
Serviceberry, Utah
Winterfat
70
37
74
80
30
60
60
53
64
57
63
55
60
60
59
15
45
38
26
16
63
77
55
70
90
56
21
45
40
35
105
63
45
180
49
42
63
42
74
48
48
42
90
330
104
14
84
70
91
93
46
82
87
68
83
75
73
72
70
61
75
36
82
76
39
24
80
94
84
91
365
70
35
180
120
49
365
112
180
365
63
56
70
91
365
104
104
63
180
365
210
28 a
Percentage of seed that germinate during a specific time interval that is determined by the peak of germination.
b
Percentage of seed that germinate during a period of time ending when essentially all germatable seed have germinated.
c
Number of accessions used in determining results. Two 100 seed samples per accession were evaluated.
d
Percent hard seed in parenthesis.
e
Fifty percent fill, all other species 95 to 100 percent fill.
22
36
14
4
20
8
6
8
4
18
30
16
18
7
18
12
32
12
60
8
12
10
24
A mature, viable nondormant seed (fig. 1) will germinate (fig. 2) if placed under favorable conditions of moisture, temperature, gas exchange, and light (for some species). There is an interdependence between these factors as well as between age of seed and storage conditions. The conditions that allow germination to occur and the time required for germination can vary dramatically between seed lots of a species (Meyer and Monsen 1990; Meyer and
Pendleton 1990; Meyer and others 1987, 1989; Stevens and Jorgensen 1994; Young and others 1984d).
Figure 1—Mature, viable antelope bitterbrush seed.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004
Figure 2—Germinating antelope bitterbrush seed.
725

Chapter 26
The cells of the germinating seed cannot carry on the vital process of germination without sufficient water. The rate of water absorption is largely dependent upon the degree of seedcoat permeability and availability of water. Seedcoat permeability and rate of water uptake can be increased in some species by mechanical, chemical, or hot water treatments (see chapter 24). Seeds of some species will absorb the amount of water required for germination in a short period; others take a much longer period. Rubber rabbitbrush will absorb the amount of water required for germination in about 36 hours, whereas seed of blue elderberry requires a much longer period: 180 days or more.
Too much water can be harmful to some seeds. Most can be soaked in water for 3 to 5 days without decreasing germination, but care should be taken if seed is soaked for longer periods.
Seeds of many species can germinate over a wide range of temperatures. Others germinate only within narrow temperature ranges (Schopmeyer 1974b). Seed of several plant species have the capacity to germinate at temperatures close to 32
∞
F (0
∞
C). Right after snow melt, soil temperatures are generally low and soil water levels are high. Under these conditions, those seeds that germinate at low temperatures have a good chance for survival, with adequate moisture being available for continued growth.
Knowing the temperature or combination of temperatures at which a species will exhibit maximum germination can help in determining the most ideal time to sow the seed. Optimum germination temperatures have been determined for a number of shrubs (Allen and others 1986a,c, 1987; Dettori and others 1984; Evans and Young 1977a; Springfield
1972a; Young and others 1981a; Young and Evans
1981b), cool season grasses (Allen and others 1986b;
Young and Evans 1978a, 1981a, 1982, 1984; Young and others 1981a), and forbs (Allen and Davis 1986;
Allen and others 1986b; Young and Evans 1979).
Extreme high temperature, such as in a fire can increase germination and emergence of species like buckbrush, smooth sumac, and lodgepole pine. Rupture of the seedcoat structure and heat inactivation of inhibitors are possible explanations for the effect fire has on seed germination (McDonough 1977).
Most seeds will not germinate when the soil is too wet, when seeds are planted too deep, or when conditions limit the supply of oxygen. Oxygen has to be present for germination to take place. A low rate of
726
Seed Germination oxygen uptake permits only the earliest stages of germination to occur. If a continual source of oxygen is not available, germination will stop and the seed will die. Oxygen is also essential for normal seedling development. Oxygen requirements can affect seeding time, seeding depth, and selection of areas to seed.
The rate of oxygen absorption during seed germination and seedling development is highly variable among species (Schopmeyer 1974b).
Under natural conditions, some seeds become buried and germinate without light. However, light is essential for seed germination of many species. Depth of seeding should be controlled as well as possible when sowing seeds of species having a light requirement (Schopmeyer 1974b). Indian ricegrass, western wheatgrass, and Great Basin wildrye are a few species that germinate best in the dark (seed covered).
Mountain brome, slender wheatgrass, blue grama, big sagebrush, and forage kochia are species that require light to germinate.
Another factor encountered in the germination process is afterripening or a continuation of the maturing process after harvest. There are a number of grasses, forbs, and shrubs that exhibit afterripening
(Stevens and Jorgensen 1994) (table 2; also see chapter 24). Seed that has been collected before fully ripening, or seed freshly harvested can, initially, exhibit low germination that will increase after a period of air-dry storage. This process hardens the embryo, and in some instances helps increase the ability of the seed to absorb the water needed for the germination process. Whether or not afterripening occurs depends upon a number of factors, including site differences, degree of seed maturity at harvest, conditions of storage, and ecotypic differences within species (McDonough 1977).
Viable and uninjured seeds of most shrub species will not germinate without seed dormancy being broken or overcome. The degree of seed dormancy varies between species (fig. 3; table 2; also see chapter 24).
For example, forage kochia and winterfat only require afterripening, whereas, wildrose and blue elderberry require 1 or 2 years or cold moist stratification to break dormancy. Most grasses exhibit little dormancy.
An exception is Indian ricegrass (Young and Evans
1984), which exhibits a profoundly dormant embryo.
Seed of most forb species, with the exception of the legumes, posses a moderate level of dormancy. Many
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004

Chapter 26 Seed Germination
Table 2—Mean percent germination of seed from 39 plant species after 2 to 25 years of storage in an open warehouse (Stevens and Jorgensen 1994).
Species Source 2 3 4 5
Years of storage
7 10 15 20 25
- - - - - - - - - - - - - - - - Percent germination a,b,c,d
- - - - - - - - - - - - - - -
Grasses
Intermediate wheatgrass
Smooth brome
Winter rye
Forbs
Alfalfa
Washington
Colorado
Idaho
95
70
89
96
71–
88
93
52
82
94
39–
75–
80
15
56
78–
11
48
63
3
32–
13
1
2
Balsamroot, arrowleaf
Balsamroot, cutleaf
Burnet, small
Cowparsnip
Eriogonum, Wyeth
Flax, Lewis
Globemallow, gooseberry
Goldeneye, showy
Ligusticum, Porter
Lomatium, Nuttall
Lupine, mountain
Lupine, silky
Penstemon, Palmer
Salsify, vegetable-oyster
Sweetvetch, Utah
Canada same + hard seed
Paradise Valley, NV
Bountiful, UT
Ephraim, UT
Pleasant Cr. Canyon, UT
Brigham City, UT
Ephraim, UT
Benmore, UT
Ephraim Canyon, UT
Ephraim Canyon, UT
Ephraim Canyon, UT
Ephraim Canyon, UT
Ephraim Canyon, UT
Ephraim Canyon, UT
Mt. Pleasant, UT
Orem, UT
69
58
97
83
66*
7
18
41
65
59
69
92
40
76
95
42
35 28–
88*+ 93
7 8–
51*+ 87
75
94
17
91
2
73
77
99
81
72*+ 85
7 6
17
28
11
24
65
67
69
100
66
58
93
9
13
36–
73–
60–
99–
79–
66–
55–
75
92
37–
20–
96–
1
90–
83
6
13–
13
37–
26
86
65
46
25
70
79
20
4
82
0
64–
8
28
85
50
70–
7
1
0
31–
40
77
86–
1
0
87
0
16–
66
71
0
0
88–
0
5
25
6
0
0
2
13
92–
13
16
Shrubs
Bitterbrush, antelope
Bitterbrush, desert
Ceanothus, Martin
Cliffrose
Currant, golden
Ephedra, green
Ephedra, Nevada
Hopsage, spineless
Mt. Dell, UT
Bishop, CA
Manti Canyon, UT
American Fork, UT
Manti, UT
Manti, UT
Wah-Wah Valley, UT
Escalante, UT
Indian apple Ephraim Canyon, UT
Mountain mahogany, curlleaf Mayfield, UT
Mountain mahogany, true
Rabbitbrush, whitestem
rubber
Sagebrush, basin big
Ephraim Canyon, UT
Richfield, UT
Sagebrush, black
Saltbush, fourwing
Serviceberry, Saskatoon
Serviceberry, Utah
Snowberry, mountain
Winterfat
Ephraim, UT
Manti, UT
Panaca, NV
Spring City Canyon, UT
Henrieville, UT
91
97
Spanish Fork Canyon, UT 80
Corona, NM 90
48
88
90
87
79*+ 86
78 86
3 5
80*+ 89
92
93
92
42
67
63
80–
73
81–
32
42
63
65
65–
82
66
47
80
99
64
83
87
80
5
–
92
91
86–
42
61
34–
67
55–
40
94
80
12
89
28
84
85
57–
37
80
68–
14
70–
34–
40
91
99
92
18
88
69
10+
84
80
89
13
39–
76
46–
11–
24–
5
50
85–
96
80–
7
88
73
40
89
27–
82
91
6
21
69
25–
7
1
1
43
72
90–
44–
0
85
65
36–
91–
6
88–
85–
0
10–
64–
3
0
0
0
37–
76–
67–
8
0
84–
61
5
66
2
24
79
0
–
44
0
0
0
0
18
10
0
1
5
74– a
Results based on four samples of 100 seeds each at 98 percent or better fill and 100 percent purity, except fill for fourwing saltbush (52 percent fill) and Martin ceanothus (59 percent fill).
b
Asterisk (*) indicates significant afterripening.
c
Plus sign (+) indicates significant increase in germination between adjoining years at the 0.5 level.
d
Minus sign (–) indicates significant decrease in germination between adjoining years at the 0.5 level.
0
0
11
0.3
0
8
0
77
0
0
2
74
60
6
63
0
28
0
0
75
–
0
6
0
11
0
0
8
–
73
78
0
0
69+
0
–
76
0
0
1
0
21
0
0
0
2
67
71
0
0
83
0
0
1
0
0
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004 727

Chapter 26
A C
Seed Germination
B D
Figure 3—Mean germination over time of multiple accessions (number of accessions listed in parenthesis following common name) of selected grasses, forbs, and shrubs in the dark at 34 to 38
∞
F (1.0 to
3.3
∞
C). Two samples of 100 seeds each examined for each accession.
A. Bluebunch wheatgrass (8), fairway crested wheatgrass (8), meadow brome, ‘Regar’ (6), intermediate wheatgrass (24), and pubescent wheatgrass (10).
B. Orchardgrass (7), and orchardgrass, ‘Paiute’ (16).
C. Great Basin wildrye (18) and Russian wildrye (12).
D. Bottlebrush squirreltail (8), smooth brome (6), and hard sheep fescue (12).
E. Cicer milkvetch (18), arrowleaf balsamroot (8), and blueleaf aster (8).
F. Utah sweetvetch with seed out of loment (10), and Utah sweetvetch with seed in loment (20).
G. Yellow sweetclover (22), Palmer penstemon (10), and Lewis flax (32).
H. ‘Ladak’ alfalfa (30) and small burnet (10).
I. Nineleaf lomatium (8) and sweetanise (8).
J. Mountain lupine (16) and silky lupine (10).
K. Wyoming big sagebrush (12), basin big sagebrush (36), mountain big sagebrush (32), and black sagebrush (14).
L. Antelope bitterbrush (40) and cliffrose (18).
M. Winterfat (24), forage kochia (30), and fourwing saltbush (61).
N. Whitestem rubber rabbitbrush (22), green ephedra (18), and true mountain mahogany (20).
O. Curlleaf mountain mahogany (16) and black chokecherry (8).
728 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004

Chapter 26
Figure 3 (Con.)
E
F I
H
Seed Germination
G
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004
J
729

Chapter 26
Figure 3 (Con.)
K
L
N
Seed Germination
O
730
M shrubs exhibit considerable seed dormancy. Time required for germination to occur varies between species and among accessions within a species (tables 1,
2, and 3; fig. 3) (Meyer and Monsen 1990; Meyer and others 1987, 1989; Stevens and Jorgensen 1994). Species that require more than 4 weeks to germinate should be fall-seeded to allow the seed sufficient time to overcome seed dormancy. This will also ensure that germination occurs at a time when the seedling can take full advantage of available seasonal soil moisture. Species exhibiting little dormancy can be springseeded if the date of seeding allows sufficient time for germination and seedling establishment prior to the usual soil drying experienced as the growing season progresses.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004

Chapter 26
The life span of seeds is affected by many variables such as: (1) the inherent nature of individual plant species; (2) condition of seed at harvest; (3) cleaning techniques; (4) storage conditions; (5) age of seed;
(6) degree of infestation by disease organisms and insects; and (7) exposure to harmful chemicals. Fluctuating seed moisture content and high temperatures are especially damaging to seed longevity. Storing dried seed at low temperatures in vapor-tight containers will preserve seed viability for extended periods of time. Seed of forage kochia, dried to a 7 percent moisture content, and stored at room temperatures in airtight containers, have exhibited over 90 percent germination after 3 years. Undried seed stored at
Seed Germination room temperature had only 14 percent germination after 3 years (Jorgensen and Davis 1984). In general, seed with hard coats and low water content are longerlived, while seed with either relatively high water content, soft seedcoats, or both are shorter-lived
(Quick 1961). There are exceptions to this generalization. Stevens and Jorgensen (1994) have reported on the longevity of many commonly used Intermountain species (tables 2, 3).
Most species have a wide range of distribution, some larger than others. Populations of the same species growing under different climatic and edaphic conditions can exhibit different germination requirements.
Table 3—Percent germination of the same seed lots for grass, forb, and shrub seed the year of collection and following various years of storage in an open warehouse (Stevens and Jorgensen 1994).
Common names 0 5 6 7 8
Years of storage
9 10 11 12 13 14 15
- - - - - - - - - - - - - - - - - - - - - - - - - - - Percent germination a,b,c,d,e
- - - - - - - - - - - - - - - - - - - - - - - - - - - -
Grasses
Brome, smooth
Fescue, meadow
Needle-and-thread
Ricegrass, Indian
Ricegrass, Indian
Spike muhly
Wheatgrass, tall
Wheatgrass, tall
Wheatgrass, tall
Forbs
Astragalus, giant
Crownvetch
Goldeneye, showy
Goldeneye, showy
Goldeneye, showy
Milkvetch, cicer
Milkvetch, cicer
Penstemon, Eaton
Penstemon, Eaton
Penstemon, Palmer
Penstemon, thickleaf
Sweetanise
91
69*
88
55
9*
14*
72*
85
85
88
41*
44
30*
39
73
51*
63*
71*
89
74
94
94
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
+
–
0
+
+
+
0
0
0
+
+
–
0
+
–
0
0
+
+
–
0
0
63
0
0
62
0
0
0
89
0
0
0
89
0
0
0
0
0
0
0
0
99
0
0
0
0
0
0
0
0
70
0
65
0
0
0
0
0
0
0
0
0
0
0
0
0
0
91
87
92
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
63
0
0
0
0
0
75
0
0
0
0
0
0
0
0
0
0
0
Shrubs
Buffaloberry, silver
Honeysuckle
Indian apple
Indian apple
Oregon grape
Peashrub, Siberian
85
57
67
58
25
88
0
0
0
0
0
0
0
–
–
0
0
85
0
0
0
58
0
0
0
0
49
0
0
0
88
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 a
Results based on two samples of 100 seeds, each at 100 percent purity.
b
Asterisk (*) indicates significant afterripening.
c
Plus sign (+) indicates significant increase in germination between germination years at the 0.05 level.
d
Minus sign (–) indicates significant decrease in germination between germination years at the 0.05 level.
e
Zero (0) indicates no data.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
31
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
82
87
82
0
44
0
23
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
68
0
0
0
0
0
0
0
0
0
49
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004 731

Chapter 26
In work with rubber rabbitbrush, big sagebrush, and hopsage, clear relationships between collection site climate and seed germination patterns have been found (Meyer and Monsen 1990; Meyer and Pendleton
1990; Meyer and others 1987, 1989). Seed source should, therefore, be considered when purchasing seed. Seed from sources similar to that of the proposed planting site should be given preference over sources from locations having significantly different environmental conditions.
Seed Germination
Often, germination percentage of a species from the same site will vary between years. Generally, percent germination is higher during years of high seed production than in years of poor seed production. Antelope bitterbrush collected in central Utah during high production years usually exhibits 95 percent or more germination, but during years of poor seed production the germination has varied from a low of 8 percent to a high of 68 percent.
732 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-136. 2004