Wildflower meadow seeds can be sown at any time of the year but usually spring or autumn are best. In winter the risk of extreme cold, wet weather is high which can reduce the chance of a meadow seed mix germinating successfully.
Some meadow seeds such as primula species and Yellow Rattle will not germinate until they have undergone a period of winter chilling. For this reason it is sometimes stated that wild meadow seed mixes benefit from an autumn sowing.
As with a perennial meadow seed mix, some annual flower meadow seeds such as Corn Poppy will also benefit from winter chilling. The timing of a sowing can therefore have an effect on the overall balance of species, after a wildflower meadow seed mix has germinated.
In the wild, meadow flower seeds ripen and shed mostly during the summer and autumn months. An autumn sowing probably mimics this more accurately and is at a time when soils are generally still warm and in a workable condition.
There are of course exceptions to the normal rules. In a particularly cold wet autumn, the germination of certain meadow flower seeds could fail. However this is unusual and in most cases, a sowing of meadow mix seeds between March and mid October will usually be successful.
Overall the greatest success will be obtained when soils are moist and workable and are at a temperature conducive to germination of the various wild flower meadow seeds. The need to germinate individual seeds e.g. Yellow Rattle, should always be treated with lesser importance than need for good seedbed preparation. The latter will have always have a greater bearing on overall success and result in the germination of a greater range of wild meadow seeds.
When planning a meadow, bear in mind that good seedbed preparation is normally easiest in spring or autumn and weather conditions at the time of sowing can effect overall results.