Jude,I have had tulips in pots for 3 years now.I cheat and just cut the green down and plant other plants around them.I add slow release fertiliser to the pots every now and then to help the potting mix .some times I will give the plants a little feed of thrive all so.I am removing the bulbs soon as it is their 3d year and will store them and then put them in the garden for the next Spring.I will start again with fresh potting mix and bulbs for the pots.