Lilac problems- another tale of woe!

I have a little grafted variegated lilac with the most beautful pale lavender blue flowers. I kept it in the greenhouse over winter as it was so cold, and it has no flowers this year.
It does have a lot of soft growth, which will have to be trimmed. Any chance of these bits rooting? And if they did, would they survive on their own rootstock?
I have another lilac which was given to me 4 years ago as a well established plant, and the first year I had it it flowered. Since then it hasn't produced a single flower. I haven't pruned it as I believe they flower on the previous years' growth. Should I give it more time or consign it to the back of the garden? It is a very pretty dark red double, and I love the smell of lilacs.
The only one flowering this year is a sucker of my neighbours' white one! :rolleyes:

 

you did right not to prune the 4 year old, give it some feed growmore or similar, it may be that it hasn't got settled in yet even though some plants will behave perfectly the first year, it is called shock flowering. it may be it needs another year or so to really get going..
I take it that it is planted outside in the ground?
your small one may have been to molly coddled over the winter, and has not had the nescersary cold spell.. most stay out, and are hardy, they do not seem to do as well in pots as they do planted out. ours are only just coming into bud

 

Thanks Rossco. They are both in pots so I will plant them and feed them. I hesitated about planting the 4yr old as it's quite big now and if it doesn't flower it would be a waste of effort, but you're probably right about the pots!
The little one was left out the previous year and it did flower so I think you're right there too. I was worried that being variegated it wouldn't be as hardy.