Cut tulips continue to grow because of phototropism. When cut and placed in a vase, the tulips bend towards the light, and so they elongate.
Tulips Lillies
You cut a tulip at the very end of the stem at a 45 degree angle. You can cut the stem as short as you want to put in a certain size vase after you have cut it properly from the ground.
Cutting and wrapping tulips is a very delicate process. The following website offers some tips and tricks to help your tulips last longer, http://gardening.about.com/od/craftsanddecor/qt/TulipCare.htm
tulips (two lips...)
If you mean "Holland tulips", it means tulips from Holland.
There are no specific collective noun for tulips. I have seen suggested, an explosion of tulips and a tiptoe of tulips. However, any noun suitable for the situation can be used, for example, a field of tulips, a bouquet of tulips, a bunch of tulips, etc.
If you are saying that "1 in 4" of the tulips are red, the answer would be 4 of the tulips are red.
No, tulips are multicellular organisms.
Tulips
Tulips are angiosperms.
Tulips are bulbs