Weather and growth of plants

We consume a lot of coriander leaves and for the past few years I have been trying to grow coriander in all kinds of seasons; generally summer is supposed to be the good season for vegetables in Melbourne. One year I sowed the seeds in the middle of April so that the plants were established before the onset of winter. Generally they have been lasting until November. Thet start seeding in Ocober but the lower leaves are edible until the middle of November. Generally they seem to grow quite big, some were about 6-7 feet tall this year. Those I sowed in November grew only one foot tall and have seeded already. Time to sow the coriander seeds again.