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Seeds

Tsuga heterophylla

Western hemlock

Storage characteristics

Intermediate 

(?)a

Storage moisture content and temperature

9-12% @ < -5°Ca

Dormancy characteristics

Shallow

Pre-treatment method

6 (3-9) weeks cold (c. 4°C)

See pretreatment of shallowly dormant species

Efficacy of pretreatment / remarks

Generally effective, a significant proportion of live seeds should germinate

Approximate date to initiate artificial pre-treatment (for 1 March sowing) 18 January

Storage characteristics

Intermediate – seeds that can only be partially dried or need very slow, careful drying. They deteriorate more quickly than ‘orthodox’ seeds but more slowly then ‘recalcitrant’ seeds.

Orthodox – seeds that can be dried without harm, and once dried can be frozen, stored for years with little deterioration and relatively easily revived.

Recalcitrant – seeds that cannot be dried or frozen and are therefore short-lived.

(?) – indicates storage characteristics are not yet fully understood.

a Maximum advisable storage c. 3years @ c. 10% moisture content & -10°C

Pre-treatment method

Figures in brackets indicate that different seedlots often require different pretreatment durations. There are three potential courses of action:

  • Adhere to the pretreatment duration in bold, with the knowledge that the maximum potential germination of the seedlot may be sacrificed for the sake of simplicity.
  • Inspect the pretreating seed regularly. Sow when c. 10% of seed is chitted, with the hope that this is indicative that the remaining seeds are now close to germination.
  • Inspect the pretreating seed regularly. At suitable intervals, remove chitted seeds (by hand, flotation, and/or sieving). Sow chitted seeds and return balance to pretreatment until no more seeds germinate.

Practice Guide

Raising Trees and Shrubs from Seed (PDF-648K)

Forestry Commission Practice Guide 18.

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