Lupins are easy and quite quick from seed, flowering in their first year if you sow them really early, and seed of individual colours is available from www.chilternseed.co.uk . Their catalogue is a good read. The Band of Noble series are excellent. Lupin 'Tutti Frutti' and 'Morello Cherry' from www.thomson-morgan.com are also good. I am looking for the palest of pale pink for my 'ice cream' bed of cool pinks and white, so have sown a packet of Band of Nobles mixed in the hope that there will be one or two in there, then I'll propagate from them by basal cuttings in the spring.
Lupins last 3 to 4 years here before fading out, and the tree lupin - lovely thing as it is - is so prone to the giant lupin aphid that I gave up on it - so silver it is for filling the May gap and for their stately demeanour and delicious range of colours.