asparagus,best time to plant?

have just bought some connovers collossall on a whim,not knowing when to plant.
seeds by the way,it says on pack sow may,would  it hurt to sow them now especially with it being so warm?.i know i cant harvest for two years.
how would i be best to prepare the soil any different from my other veg?
ta poppie

I sowed mine later than the packet said poppie, and they've come up a treat