If they're to be arranged in vases, it helps to know the three kinds of shapes used in design: linear, focal, and filler.

The linear flowers are long & straight, with many blossoms close to the stem. These form the framework of the floral design. Some examples you might try: liatris, chicory, Bells of Ireland, delphinium, larkspur, salvia, glads, snaps.

Focal flowers are used as centerpieces that anchor the design, direct attention: showy flowers like sunflowers, lilies, cabbage rose, hydrangea and peonies.

Filler flowers are used to transition between the linear and focal flowers, and soften the lines. Look for clusters of flowers on a single stem or flower head. Examples: sedum, yarrow, lady's mantle.

Filler foliage is also used extensively, inc. ferns and grasses, evergreen boughs.

Also consider formality/informality of the flowers used.
Coneflowers (and other disks) inc. rudbeckia and montauk daisies are mainly used to make wildflower bouquets.

Think about how you will be using the flowers, how often you will be changing the design (weekly?), will pollen be a problem indoors.

Thank you prairiegirlz5, that's exactly what I wanted to know! I'll keep all that in mind as I design the garden.

Formal or informal isn't important, there will be occasions for both. Another consideration is the availability of certain flowers. We have very little money for this project so I was going to ask for donations this spring when my gardening friends are dividing their perennials.

I'm going to use your suggestions when I send out my requests--I want to make sure I'm not just getting flowers people want to get rid of.

Don't forget to ask for volunteers to dig and plant the garden! I know lots of people on this forum are into growing and selling cut flowers, more so than me. I'm glad I could help.

Also, think about the size of your arrangements.. If they are large, you will want to plant those plants that produce larger flowers, large sunflowers, giant dahlias, hydrangeas..etc.. but if these are for small arrangements you can plant the little Teddy bear sunflowers, the small dahlias, zinnias.. And don't forget roses--yes some roses can be carefree, produce repeatedly and have tons of var. A climbing rose can take up very little 'floor' space in a small garden.. Place a small trellis and train it up.. it will produce tons of flowers for cutting..

queenbee_1, I just noticed your post. What wonderful ideas, I never thought of roses but they would be super easy since they are in a fence and won't need to be protected from the deer. I'll have to run it by the deacon but I think we can do that.

Thanks so much for your reply!

Our church has extensive gardens around it to cut for our altar and for our events - plus two of us grow cutting gardens for it also (and for weddings etc.). It is extra special to be able to provide a true thanks for the gifts we are given.