They don't need much looking after - I have 2 growing in dappled shade, not full sun - remember they grow in woodland settings naturally. When the flowering spike has finished cut it off and you may be lucky and get another one grow. If you want it to self seed leave the flower spike on and the seeds will eventually fall to the ground and hopefully grow!
Perfect answer from Ann, but don't be disappointed if they don't flower in year one as they are biennials; once established however they will look after themselves for ever more and will self seed producing a selection of plantlets across the garden as well as doubling in original size.
Just in case you're not aware, the entire plant is toxic (including the roots and seeds), although the leaves of the upper stem are particularly potent, with just a nibble being enough to have serious effects.
Wildflowers used to and well up for muscling their way up and over any competition. Very hard to kill, but they are highly toxic, take care if children and / or pets have access.
handle wearing gloves. as sap is toxic (used as medicine to slow fast heart rates)...otherwise reasonable soil part shade once they flower and the seeds are ready shake all round the garden and you will have them forever
Might look rather out of place because of that height.....I will probably give one or two of the three away! -Slowing my heart rate sounds beneficial!!
If you cut back the stems of faded blooms, they will repeat flower all summer. If you don't want them to self seed, make sure that all faded blooms and seed heads are remove before they get the chance to seed.
If you can leave the flower heads on at the end of the summer, they will happily seed the garden. I leave some of mine, and it's lovely to see them flowering in odd places next year. If you've got different colours, they may cross-pollinate and produce completely different colours next year. I always pull mine up after a couple of years as they can go all 'manky'. I love them.
treat them as biennials and plant second year plants again next year so you have flowering stage and rosette forming stage plants at the same time for year 3 onwards