Treatment of messmate (E. obliqua) seed to enhance nursery production of seedlings.  M. D. Murray.  February 2005.  22pp. (unpubl.)

SUMMARY

Messmate (Eucalyptus obliqua) is a major commercial species that is indigenous to forests of south-eastern Australia. Following harvesting, regeneration of forest stands is achieved by natural seedfall, direct sowing or, occasionally, planting of nursery-grown seedlings.

Messmate has proved problematic for nursery production. The relatively uniform size of seed and chaff particles often results in sowing of non-viable particles, particularly when using automated sowing systems. The prolonged duration of germination, in comparison with most other commercial eucalypts also often means that seedlings are not uniform in size.

The use of sieving, cold stratification and pre-germination treatments in association with separation by specific density were trialled to determine if the ratio of seed to chaff can be increased and the time span of germination reduced. A number of pre-germination media were tested including smoke (as a natural component of the environment associated with eucalypt regeneration), and potassium nitrate (used in nurseries to delay germination and improve uniformity).

The results were variable. Pre-germination in smoked water or distilled water followed by specific density separation improved the percent of viable seed particles which would decrease the likelihood of an empty pot. However they did not always improve the germination energy of the seed. Smoke was often associated with an unacceptably high rate of mould formation that would lead to a loss of seeds. Cold stratification for 6 weeks was most effective in increasing the rate and total percent germination, while sieving of seed prior to germination increased the purity, but decreased the number of seeds per kilogram of the seed lots.

A combination of cold stratification and pre-germination in water is likely to be the most useful treatment to improve the production of messmate seedlings. However, care needs to be taken to avoid damage to the seeds and that the selection of specific seeds and seedlings does not result in reduced genetic variation, and thus site adaptability, in the species across its range.