Depends your grow zone. I'm in zone 7 in the US. I would plant first week in April.

The best advice is from the RHS, so if you've not seen it, link below.

https://www.rhs.org.uk/advice/grow-your-own/vegetables/asparagus

You can probably plant in March, but best to use crowns you've bought rather than growing from seed, you get quicker results. Info regarding preparation prior to growing is also in the link.

Yes, roots start giving a crop in 2-3 years, while seeds take a year longer. Some higher yielding varieties are also available from roots, but not by seed. The main advantages to growing from seed are subtle, including reduced chance of virus infection, and conservation of genetic diversity.

thanks all for advice