They will need staking if they are the tall single stemmed ones, but be careful to loosen the string or ties regularly, or like what happened to mine, one day, the string will cut clean through the stem, very neatly, and all that love will have been for nothing!
I do plant mine a little deeper, but don't over water as they will rot off quite quickly. Mine will be going up to the plot mid to late April - I am in Essex.