Conifers – Root Protection

The Root System

The Root system must be well developed by good nursery practice influenced by the natural characteristics of the species/cultivar, taking into account its age and growth rates under the cultural and soil conditions within which it is growing.  The system must not show any coiled main roots close to the collar, nor any physiological damage.

The root system must not be allowed to dry out at any time.

NPS Conifers Root Protection

Plants are supplied:

  • bare-root (bagged
  • cell grown
  • rootballed (balled and wrapped)
  • container grown
Bare root Conifers

Bare root conifers should, generally, be not more than three years old.  All bare root conifers (up to 40 cm overall height) must be supplied totally enclosed in bags.  Above this height, the roots only are to be enclosed.  Ideally the bags used should be manufactured from co-extruded polythene – black on the inside and white on the outside.

Conifers must be supplied bagged unless any other protection (rootball, container grown) for the root system is specified.

Cell grown Conifers

Cell grown conifers are usually grown from seed.  The plant is grown in a container (a cell) and then supplied with a complete rootball, bundled together, protected with plastic and dispatched in boxes.

Cell trees are specified by ROOT VOLUME (Container size), HEIGHT and ROOT COLLAR DIAMETER.

As with all plants, specifications cannot be rigid since growing conditions will vary from year to year but the information in this specification gives the general standards for growing cell plants.  Again, as for other stocks, larger cell grown conifers can be grown on contract.

Rootballed conifers
rootballed conifer
Rootballed conifer

Field grown conifers are usually supplied with a rootball.  Rootballs must be firm and solid and the roots must penetrate the whole ball.  They must be enclosed in hessian (burlap). The size of the rootball must be appropriate for the species/cultivar and its age and growth rates under the cultural and soil conditions within which it is growing.  The rootball must be free of perennial weeds.

The following sizes can act as a guide:

Diameter
3x girth at the root collar Typical conifer
3x girth at 1 metre Standard form

 

For Specimen conifers, the root ball will be additionally protected with ungalvanised wire netting, wire basket, spring ring, root control bag, tree cradle or custom built container.  All materials used to support root balls must decompose within eighteen months of planting and not constrict the continuing growth of the plant.

Container grown Conifers
Container grown conifer
Container grown conifer

Container grown plants should have been grown in the container for sufficient time for the root growth to have substantially penetrated the medium but not be root bound. The rooting must be well balanced in accordance with the container size.

Plants are to be centred in the container, well rooted, firm and moist on delivery, with the growing medium coming within a suitable depth of the pot rim, taking into account the size of the container and the age since potting.

The surface of the growing medium shall be free from weeds.  Plants shall be supplied in rigid containers or polybags.  Container grown plants are defined by ‘C’ followed by a number indicating the volume in litres, e.g. C5.

Forest conifers are also grown in Japanese Paper Pots (JPP’s).  These biodegradable containers are used for raising seedling forestry stock.