N. Understock
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General Specifications:
This section is to cover plants (primarily shade, flowering, fruit, and nut trees) graded by caliper generally used for grafting and budding. For plants graded by height see  Section 2.5.2 and  Section 5.2.2.

The quality of all understock offered is assumed to be normal for the species of variety unless otherwise designated. It is essential that the stem be reasonably straight.

Method of Measurement
Caliper shall be taken at the collar or ground line unless height is specified by purchaser, who must indicate if he or she wants height only or height and caliper.

Age is not important when caliper is specified; however, it may be requested by purchaser.

12.2 Grading Increments
International specifications will apply as seen in Section 2.4 of these standards followed by the grading measurement in millimetres.

Example: 1/0  5 mm

1.5 mm    15 mm
3 mm        16 mm
5 mm        20 mm
6 mm        22 mm
8 mm        25 mm
10 mm

Types of Plants

Seedlings with Limbs
There will be no limbs on one side of the seedling for at least 5 cm above the collar to ensure a budding or grafting area.

The root system and the plant shall be free of mechanical, chemical and climatological damage.  The plant must have a length of 40 cm including the root system.

One year cuttings must have a one year growth of at least 15 cm.

Two year cuttings must have a growth of 15 cm.

The plants need to be sufficiently straight.
Root Descriptions
In case of apple and pear seedlings, where the root descriptions is given as branched or straight, the following shall apply:
Branched Root: Not less than three root branches must be present within 13 cm.

Straight Root: The root shall carry the minimum caliper of the grade fore not less than 15 cm of the collar.

Vegetatively Propagated Plants

From Layering
Stem caliper shall be taken 25 cm above the bottom of the layer (basal cut).

Roots - a minimum of 3 root nodes, each node containing at least 1 root.
Hardwood Cuttings

Caliper must be taken at the collar or ground line.
Softwood or Micro-Propagated
Caliper must be taken at the collar or ground line.

Any root stock not meeting the above specifications should be labelled “unclassified”.

Shade and Flowering Tree Seedlings
Shade and Flowering Tree Seedlings, when used for understock, are graded by caliper as per this section.

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