Purple fountain grass (Pennisetum setaceum "Rubrum") grows in clumps 3 to 4 feet tall and 2 to 3 feet wide. It sends purple flower spikes up to 12 inches long. This plant is a perennial in USDA zones 9 to 11, which means that it overwinters where the temperatures stay above 20 degrees F. Most often, however, people grow it as an annual.
Fill small seeding pots with half peat and half perlite in early spring. Plant the seeds 1 inch deep in the potting medium and 1 inch apart. Tamp down the soil above the seed to ensure contact.
Water the seeds deeply. Secure a plastic bag over the seeds with a rubber band. Place the seeds in a warm dark area, keeping them moist until they sprout.
Remove the plastic bag and transplant the purple fountain grass into larger pots when they reach 3 inches high. Plant the grass in the same potting medium at the same height as they were in their original pots.
Find an appropriate area to plant your purple fountain grass. This grass prefers full sun or partial shade in almost any soil.
Transplant the purple fountain grass outdoors after the danger of frost passes. Again, plant the grasses at the same height they resided in their pots. Space multiple plants 36 to 60 inches apart.