Yes they do. But cut the flower stems off just as the petals fall off. This way the tulip will spend its energy making bulbs instead of seed. Also, don't touch the leaves. They are solar panels,so to speak, which provide the energy it takes to produce more bulbs. I might say that this is a very simplistic answer since bulb production also depends upon a lot of other variables such as soil type,depth planted, type of tulip eg hybrids don't produce bulbs as well .....etc other members will surely provide info on that....Best Regards

They seem to do better in ground thats fairly dry over the summer. And they are more likely to flower again if you feed them with tomato fertiliser until the leaves die back.

Like a lot of bulbs they appreciate being given a baking in summer but we are at the mercy of mother nature on that one. The species tulips do far better than the cultivars from my observations.