This is beautiful!! I have a small specimen of this- two nights ago it was eaten down to about 8 inches by an open range (friendly?) cow. My fountain grass is several years old but much smaller probably due to dry desert climate. It dies to the ground each year and comes up rather late in spring.
The picture was taken when the Pennisetum was exactly six months old, in Sept 2002. In a picture when it was planted in early March '02, it is just about 1x1'. A tribute to good quality compost and a sunny location, I guess! Actually, it was getting too big, so my husband and I yanked it out in Oct. and divided it into thirds. The divisions have been cut back and put in pots. It's been two months and with moderate watering they are starting to grow again. Looks like they stay purplish-red as long as they receive occasional water. We have 3 other Rubrums planted at the same time that are more moderately sized, between 3-5' but no more than 3' across.