Table 1. Number of planting sites in different planting seasons, by tree species and geographical region. Areas were classified into two groups based on accumulated temperature sums: central Finland 1000–1200 d.d. and southern Finland >1200 d.d. (Äijälä et al. 2014).
Region/ Norway spruce Scots pine
Planting season Central Southern Central Southern
Spring 243 475 134 198
Summer 62 24 12 10
Autumn 39 43 13 17
Table 2. Average weather data for two geographical sub-regions (central [N = 6], southern [N = 7]) in Finland. Pmean – mean precipitation sum (mm), with the average of 1981–2010 in brackets; Tmean – mean temperature (°C), with the average of 1981–2010 in brackets; Tmin – mean minimum temperature (°C); Tmax – mean maximum temperature (°C). April, May and June were included in the spring plantings, July and August in the summer plantings, and September and October in the autumn plantings.
Region Planting time Pmean Tmean Tmin Tmax
Central Finland Spring 51 (36) 10 (8) –2 22
Summer 111 (68) 16 (15) 5 25
Autumn 28 (52) 7 (6) –2 16
Southern Finland Spring 49 (34) 11 (9) –1 23
Summer 80 (67) 16 (16) 6 25
Autumn 32 (58) 7 (8) –2 18
Table 3. Range of viable seedling density per hectare for the corresponding grade based on target density.
Tree species Target, seedlings/ha Grade, seedlings/ha
Excellent Good Moderate Weak
Scots pine 2500 ≥ 2375 2374–2125 2124–1300 1299 ≥
Scots pine 2200 ≥ 2090 2089–1870 1869–1300 1299 ≥
Scots pine 2000 ≥ 1900 1899–1700 1699–1300 1299 ≥
Norway spruce 2000 ≥ 1900 1899–1700 1699–1200 1199 ≥
Norway spruce 1800 ≥ 1710 1709–1530 1529–1200 1199 ≥
Norway spruce 1600 ≥ 1520 1519–1360 1359–1200 1199 ≥
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Fig. 1. Proportion of all Norway spruce (a) and Scots pine (b) plantings in different planting-result classes (weak, moderate, good, excellent), given overall (total) and separately for different planting seasons (spring, summer, autumn). Error bars show the range of proportions between southern and central Finland.

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Fig. 2. Proportion of Norway spruce (a, b) and Scots pine (c, d) sites in different planting-result classes (weak, moderate, good, excellent), given overall (total) and separately for different planting seasons (spring, summer, autumn) in central (a, c) and southern (b, d) Finland.

Table 4. Binary logistic regression model for the probability of a successful planting result. The modeling data consist of 1270 planting sites in southern and central Finland. Exponentiated estimate denotes the odds ratio.
95% C.I. for Exp(B)
Variable Estimate Std. Err p-value Odds ratio Lower Upper
Intercept 1.713 0.115 0.000
Tree species (ref. Norway spruce)
  Scots pine –1.668 0.153 0.000 0.189 0.140 0.255
Planting time (ref. spring)
  Autumn –0.117 0.321 0.716 0.890 0.474 1.669
  Summer –1.044 0.262 0.000 0.352 0.211 0.588
Region (ref. south)
  Central 0.159 0.143 0.268 1.172 0.885 1.552
Interaction (ref. spring Norway spruce)
  Summer Scots pine 1.096 0.512 0.032 2.992 0.249 1.795
  Autumn Scots pine –0.403 0.504 0.424 0.669 1.096 8.163
The reference category is: Poor
Table 5. Accuracy of classification of the planting results.
Observed Predicted Percent Correct
Poor Successful
Poor 18 312 5.5%
Successful 12 928 98.7%
Overall percentage 2.4% 97.6% 74.5%
Table 6. The numbers and proportions (%) of poor planting results, due to poor work quality and natural causes of damage, in different planting seasons for Norway spruce and Scots pine. The “mammals and birds” category includes moose, deer, bird, vole and hare damage. Other reason category includes reduced planting quality due to excessive vegetation, overwatering of the soil, rocky terrain or other terrain-related difficulties and the unknown reason category includes invalid or unclear reasons for poor plantings, respectively.
Reason for poor
planting result 		Norway spruce  Scots pine 
Spring Summer Autumn Total Spring Summer Autumn Total
Planting mistake 15 (14%) 3 (11%) 2 (14%) 20 (13%) 14 (9%) 0 (0%) 1 (6%) 15 (8%)
Poor soil scarification 29 (27%) 6 (22%) 1 (7%) 36 (24%) 14 (9%) 3 (30%) 5 (28%) 22 (12%)
Poor seedling material 1 (1%) 0 (0%) 0 (0%) 1 (1%) 0 (0%) 0 (0%) 0 (0%) 0 (0%)
Insects 5 (5%) 5 (19%) 0 (0%) 10 (7%) 6 (4%) 1 (10%) 2 (11%) 9 (5%)
Mammals and birds 8 (7%) 1 (4%) 2 (14%) 11 (7%) 63 (40%) 1 (10%) 2 (11%) 66 (36%)
Fungi 0 (0%) 0 (0%) 0 (0%) 0 (0%) 2 (1%) 0 (0%) 0 (0%) 2 (1%)
Frost 2 (2%) 0 (0%) 5 (36%) 7 (5%) 2 (1%) 1 (9%) 3 (17%) 6 (3%)
Drought 2 (2%) 0 (0%) 2 (14%) 4 (3%) 3 (2%) 0 (0%) 0 (0%) 3 (2%)
Other reason 15 (14%) 4 (15%) 0 (0%) 19 (13%) 15 (10%) 1 (10%) 2 (11%) 18 (10%)
Unknown reason 31 (29%) 8 (30%) 2 (14%) 41 (28%) 38 (24%) 3 (30%) 3 (17%) 44 (24%)