Examples: Most broadleaves e.g. ash, beech, cherry
A few conifers e.g. juniper and yew.
All these seeds (whether freshly collected or stored) are incapable of germinating under any conditions until pretreated. Pretreatment consists of incubating seeds for a relatively long period of time (8 to 64 weeks) under moist conditions. All species can be pretreated either naturally or artificially. All can be pretreated in a moisture retaining medium, a few can be pretreated without. Some need cold only (c. 4°C) others warm (c. 15°C) followed by cold (c. 4°C) - for recommended pretreatment durations for individual species - seed pretreatment tables.
There are several potential methods which can be used to pretreat deeply dormant seeds. Three are described below:
- Easy: Natural (outdoor) pretreatment/germination with medium for deeply or shallowly dormant tree seeds
- Moderately easy: Artificial (temperature controlled) pretreatment/germination with medium for deeply or shallowly dormant tree seeds
- Skilled: Artificial (temperature controlled) pretreatment without medium for deeply or shallowly dormant tree seeds.