Just to elaborate a little on the refrigeration aspect, as I mentioned above it makes a difference if the seeds are dry when refrigerated or if they are hydrated. If the seeds do not have enough internal moisture when refrigerated, they will not respond to the chilling. I've done a number of daylily seed experiments, mostly with seeds that are as genetically similar as I can get them to reduce that variable as much as I can. This first picture is of daylily seeds that had been refrigerated dry for six weeks and then started at room temperature:
The next picture is of the same number of daylily seeds, refrigerated for the same length of time but in dampened vermiculite so that they re-hydrated. Both pictures were taken a month after coming out of the fridge and being started at room temperature:
This test was to illustrate that staggered germination isn't always because they were not chilled for long enough but can be because the seeds were too dry internally to respond to the refrigeration. After a month at room temperature, germination of the dry refrigerated seeds was 24%. After a month at room temperature the germination of the damp vermiculite refrigerated seeds was 96%.
These seeds had been stored dry at room temperature prior to the experiment.
