Cold moist stratification

Some tree seeds have a physiological dormancy which can be broken by certain levels of cold or heat. Such seeds need to be treated by stratification.

In this exercise, we used seeds from Betula pendula, Acer buegeranum, Zelkova serrata - all deciduous trees native to the Northern hemisphere. We chill seeds in a refrigerator at temperature between 0 - 5 degrees celsius, to mimic the passing of winter and to gain a more even germination. Seeds need to be kept moist and so are sealed in plastic bags before being placed in the refrigerator.

Betula pendula catkins were harvested from the TAFE garden.

Samaras from Acer and Zelkova spp. were collected from the Botanic Gardens.

The seed-raising mix used consisted of equal parts of pasteurised sand, cocopeat, perlite, combined with trichodry and mini-osmocote.

A low punnet was filled with this mix and tamped down gently but firmly.

Betula seeds were scattered as a thin layer across the mix and then covered lightly with the same mix.

Zelkova and Acer seeds were placed gently by hand in the mix and again covered lightly.

These were then watered and placed in plastic bags and refrigerated as previously mentioned.

Betula pendula stratification period was from 22/4/09 - 15/5/09 (25 days)

Zelkova serrata and Acer buergeranum from 22/4/09 - 14/6/09 (55 days)

After each stratification period, punnets were removed from fridge and placed on heating and misting beds.

Betula pendula seedlings all had excellent germination rates and were pricked out on 30/6/09 :

Ref :RHS propagating plants, pg. 54