Question
Hi,
I want to make table centerpiece arrangements for my 50th B day using white and pink tulips. The vases I am using are mirrored mosaic(non see thru)about 20 inches tall. Can you tell how to arrange them?
Thank you for your time

Answer
It's going to be easiest if you use a brick of dry foam in the vase.  The brand I use is Sahara by Oasis, but there are others.  Just make sure it's meant to be a dry foam used with silks, and not a foam to be soaked with water for use with fresh flowers.

The brick should fit tightly in the container.  Use two, if necessary.  To conceal the foam, I use some spanish moss or some sheet moss stretched thin over the top of the foam.  You insert the stems right through the moss.  Try to insert the stems at least a good 2 inches to be sure the flowers hold in place.  

One of the best things about working with silks is that you can bend the stems in any direction you like.  Toward the middle, leave the stems relatively straight, but around the edges of the vase, give them a nice outward curve.

Also, don't be afraid to stagger the heights.  If they're all on the same plain, the arrangement is going to seem flat and uninteresting.  If you put a few flowers slightly deeper than the surrounding ones, it will keep the viewer's eye interested.  Additionally, I recommend to use a little bit of clustering - put a few white tulips together in some areas, a few pink in other areas, and alternate in between.  Using small groupings of like colors makes a bigger visual impact than if you distribute them completely evenly.

Ideally, the vase should make up just 1/3 of the height of the overall arrangement.  Since you're working with such a tall vase, this might not be possible.  But I would recommend to leave the stems as long as possible.  You want the flowers and the vase, because it's decorative, to gain the same amount of attention.  If the stems are too short, the flowers are going to lose any focus and appear rather unimpressive.