I have a small bed in full sun, zone 5, approximately 6 feet wide and 10 feet long. I would love to get some suggestions on a companion plant for a space of about 36 square inches in the back of the bed.

I currently have the following plants in the back of the bed from left to right:

Climbing pink flowering rose on trellis,____Empty Space____, broadleaf white flowering Rhodie

In the front of the bed I have from left to right:
Black Eyed Susans, Purple Cone Flowers, Shasta Daisies, Tick Seed

Thanks in advance! Beautiful day for gardening in the midwest today!

the rhodie flowers first, then the rose...

how about a bank of tall lillies? I have the old fashioned orange turk's caps standing up through a bed of irises and daylilles, and they make a great vertical statement.

either holly hocks or Lupines are another suggestion- again, a great vertical statement, and the lupines are about mny favorite flower in the whole world for the smell alone!

and I'd be tempted to put some annuals- verbenas, or allysums in the very front of the bed.

(actually, if you can find it, there is a perennial alyssum that makes standing bouquets of tiny yellow flowers that is one of the best foils for every other flower in the garden in the spring)