A rule of thumb for the depth of bulbs (measured from the tip not the base): The planting depth should be double the height of the bulb. If you plant your bulbs in pots rather than beds, you can also use the sandwich method and position different types above each other in layers, e.g. narcissus at the bottom, then mini tulips, then hyacinths and then winter bulbs again. If you coordinate the flowering times of the various types of flower (note the instructions), the individual layers blossom immediately after each other to create a firework-like display. By the way, you can also achieve a long flowering period with a single bulb type and species by planting the bulbs in two to four sets at an interval of ten to fourteen days.