Acer pseudoplatanus

Sycamore

Recalcitrant

Store moist @ 4°C

12 (8-16) weeks cold (c. 4°C)

Generally effective although pretreatment durations, and numbers of repeat cycles may vary significantly between seedlots

Approximate date to initiate artificial pre-treatment (for 1 March sowing) 6 December

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

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.

Forestry Commission Practice Guide 18.