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Container-grown seedlings are the most common stock types produced in B.C., however, field-grown stock types are still produced and planted to a limited degree. Most of the discussions in this guide refer to container-grown stock.

Container-grown StockTypes

A stock type name is a shorthand method of specifying seedling morphology. For a given species, a stock type name is comprised of four elements -- container type/container size/seedling age/season of planting. In selecting a stock type, first consider the desired seedling attributes in relation to site conditions, and then specify the shorthand notation as illustrated in Figure 2.

Example of stock type nomenclature.

Figure 2.   Example of stock type nomenclature. Species is interior spruce, container type is a plug styroblock, container size is approximately 4 cm wide by 12 cm deep cavity with 77 cavities per block, age is one year, and the season of planting is spring.

Table 1 provides the definitions for the various components of the stock type notation commonly in use. Table 2 lists the dimensions of the principal containers used.

Table 1.   Abbreviations and their definitions as used in container stock types

Container type PSB ­ plug styroblock
PCT ­ plug copper treated
CRC ­ container rooted cutting
PAP ­ plug air-pruned (plastic block)
PAB ­ plug air block (styroblock)
PPT ­ plug-plug transplant
Container size Approximate dimensions of cavity (see Table 2)
Seedling age Two-part code with the two parts separated by a plus sign; total equals seedling age. For example:
  • 1+0 = one year old, seeded and grown in same place
  • .5+.5 = one year old, grown half the year where seeded, transplanted once, and grown half the year in another location
  • 2+0 = two years old, seeded and grown in same place
Season of planting Sp ­ spring
Su ­ summer
Fa ­ fall
Wi ­ winter

Table 2.   Container stock type density, container dimensions, and soil volume

Container size Cavity
width (cm)
depth (cm)
Cavities/block Cavity
volume (ml)
Seedling density

211A 2.7 11.4 240 39 1130
313B 3.0 12.7 160 65 764
410 3.6 10.5 112 80 527
415B 3.5 14.9 112 93 527
412A 4.2 11.7 77 126 366
415D 4.3 15.2 77 172 366
512A 5.2 11.9 60 220 280
515A 5.1 15.2 60 250 280
615A 6.0 15.2 45 336 215

Field-grown Stock Types

Bareroot seedlings are designated either BBR for seedlings seeded directly into nursery beds (Plate 1), or PBR for seedlings sown in a container in the greenhouse and later transplanted to the nursery bed (Plate 2). Stock age is also included in the stock type notation.

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