Asparagus from seed: what next?

The packets (T & M Martha Washington) I bought said sow in mid spring - I have done but nothing has come up yet. The packet also said they take a long time to germinate. I think Kristen said theirs had germinated within days, but think they were indoors in a propagator

I spoke too soon - oh joy of joys just spied two spears poking they heads up 

Its taken just over three weeks for my outdoor sowing