Autumn sown annuals
Do you mean biennials?
I have found that over the years my methods have changed simply because I have developed and improved my facilities in particular permanent heating and protections.
The biggest killer of over wintered plants is the wet rather than the cold, when you get both of these together it is often lethal to plants.
Just think if you are wading through slush in cold weather and your footwear lets in the wet, usually your feet are much colder than they would be if wading through the slush with waterproof footwear.
So waterproofing your plant covering helps, hence the cold frame!
The frame is cold but relatively dry so creating a better environment for plants.
The main reason for sowing in Autumn is because the soil and quite often the air temperature is relatively warm meaning conditions are warm enough for germination to take place.
With plants such as wallflower and Sweet William which are biennials I like to sow these in mid to late summer so that I can pot them up and grow them on so that I can plant them out to become established prior to the onset of winter..
Personally I rarely Autumn sow because I have heat available in Jan/Feb meaning I can replicate the Autumn temperatures and have enough cool dry storage to protect the plants until they are large enough to plant out, plus they do not go through a semi- dormant stage caused by the low temperatures as with Autumn sown plants.
So to sum up I would say that what you plan to sow and what facilities you have will play a large part in your potential success.
I hope this helps you to make your mind up should you wish to have a go at this method of sowing seeds.
