GENERAL

Most conifer seed, even that which is not strictly dormant will show improved rates of germination and yield more and better seedlings when given a period of moist chilling pre-treatment.

A few species are deeply dormant, such as Taxus, and require pre-treatment over an extended period as required for a dormant broadleaf species such as Prunus avium. These more unusual types of conifer seed can be identified by reference to the seed merchant's catalogue.

Conifer seed often contains a significant proportion of empty seed.  For growth in Rootrainers as clean and uniform a source as possible is desirable.  The seed merchant can normally increase the quality by extra processing on request.  Clean graded seed with a very high germination percentage can be sown mechanically by vacuum nozzles.

SEED PRE-TREATMENT

The seed is placed in a polythene bag and several times the seed volume of cold water is added ensuring that no seed remains dry by floating.  After 48 hours the water is drained off by inverting the bag with the neck lightly tied, and the seed is stored at 1-2C for up to 10 weeks, taking care to ensure that it remains moist.  The seed can be sown any time after 3 weeks of pre-chilling when suitable growing conditions are available. Occasionally due to the action of fungus, some seed lots react negatively to pre-treatment.  For example, Picea sitchensis can be affected by cold fungus Geniculodendron pyriforme.  Affected lots can be treated with Thiram to overcome this problem.

SOWING

The Rootrainer cells should be filled to within 1/4" from the top.  The pre-treated seeds are laid on trays or newspaper and allowed to surface dry to make handling easier especially if vacuum sowing.  No heat should be applied. The sowing density depends on the seed viability which should be obtained from the seed merchant's seed test information.  For the Pinus, Picea species and Pseudotsuga taxifolia this is normally 95% or even higher after special processing.  For these species one seed per cell should result in adequate productivity.  If the viabiloity of the seed is lower as in species such as Tsuga, Larix and Chamaecyparis, this problem can be solved in one of two ways.  Either the seed can be pre-germinated in trays and one per cell pricked out, or it can be multiple seede and any excess plants thinned out later.  The size of seed will determine which alternative is chosen.  Large seeded species like Abies or Cedrus are better pre-germinated.

If the seed is sown direct it should be covered by a thin layer of sand equal in depth to the thickness of the seed to prevent drying out.  If the ambient humidity is known to be low the trays may be covered with thin polythene sheeting till the seed germinates.  Once the seedlings emerge the temperature must not be allowed to fall below OC.

CONTAINER SIZE

The smallest Rootrainer suitable for conifer production is the Rannoch.  By sowing early in March, Larix and Pseudotsuga could be grown to 30-45cm in one year.  If  larger plants are to be produced, a Sherwood Rootrainer would be more suitable.