Is Rubrum Grass an Annual or Perennial?

Rubrum grass, also known as purple fountain grass (Pennisetum setaceum ‘Rubrum’), is a popular ornamental grass grown for its attractive burgundy foliage and purplish plumes. But is it an annual or a perennial? The answer depends on where you live.

Rubrum Grass Growth Habits

Rubrum grass is considered a tender perennial as it cannot survive cold winters. It is hardy only in USDA zones 9-11 where it will return year after year. In cooler climates zones 8 and below, it will likely die back over winter.

Even in zones 7-8 rubrum grass may sometimes return in spring if given adequate winter protection such as mulch. However, its likelihood of returning each year in these cooler zones is low so it is often grown as an annual.

Overwintering Rubrum Grass

If you want to enjoy rubrum grass for multiple years you can overwinter it indoors. Here’s how

• In fall, cut the grass back to about 3 inches from the ground.

• Place the potted plant in a sunny window or basement where temperatures remain above 50°F.

• Keep the soil moist but not soggy, watering once a month.

• In spring after the threat of frost has passed, move the plant back outdoors.

This overwintering method allows you to grow rubrum grass as a perennial even in zones where it normally dies back.

Growing Conditions

• Sun: Full sun
• Soil: Well-draining
• Water: Drought tolerant, water deeply once a week
• Hardiness: Zones 9-11

Rubrum grass thrives in hot, sunny conditions. Make sure to give it plenty of space as mature plants reach 4 feet tall and wide. Space additional plants 3-5 feet apart.

Care

Caring for rubrum grass is easy. It is drought tolerant once established so only needs occasional watering. Feed in early spring with a balanced, slow-release fertilizer to stimulate growth.

In fall, cut the grass back to the ground before first frost. In zones 9-11, cut back in late winter before new growth emerges.

Annual or Perennial?

To summarize, rubrum grass is:

• A perennial in zones 9-11, returning each year.
• An annual in zones 8 and below, dying back in winter.
• A perennial in zones 7-8 if given winter protection.

So is rubrum grass an annual or perennial? The answer depends on your climate zone and how you choose to grow it. With proper care, you can enjoy this beautiful ornamental grass for many years to come.