Ornamental · Poaceae
Japanese Blood Grass
Imperata cylindrica 'Rubra'
Give it full sun and even moisture, and the blades kindle blood-red from the tips down.
Full sun
Every 5–10 days
USDA 5–9
12–18 in · 30–46 cm
Overview
Japanese blood grass earns its place in a garden for the sake of one quality: color. Its slender upright blades open green near the base and deepen to blood-red toward the tips, and the whole clump reads like stained glass when the low sun passes through it at the close of the day. A grass by family, it settles into a tidy, knee-high mound and keeps to its spot, which makes it an easy partner for a considered border.
As a hardy perennial it holds its ground through hard winters down to -20°F (-29°C) and rises again from the roots each spring, so the scene it anchors returns on its own. It rewards a full-sun position with even moisture, and its color reaches full pitch when it sits at the front of a bed or against a darker hedge or wall that lets the red carry across a space.
One trait separates this grass from the usual ornamental, and it shapes where it belongs. The red cultivar can revert to its wild green form, cogongrass, a federal noxious weed and one of the most destructive invasive grasses anywhere. It stays harmless to the people and pets who share the room around it, yet the legal and invasive side is real, and the sections below set it out in full.
Care
The short version: full sun for the deepest red, soil kept evenly moist, and a single cutback in late winter. Keep watch over the clump for any green shoots and lift them the moment they appear.
Light
Set it in full sun for the fullest color. The blades take a little shade, but past light shade the red drifts toward green, which undoes the very look you planted it for.
Water
Keep the soil evenly moist, watering about every 5 to 10 days as the weather asks. An established clump rides out a short dry stretch, though even moisture returns the best color and the strongest growth.
Soil
It settles happily into fertile, well drained loam that holds a touch of moisture. A pH anywhere from 5.5 to 7.0 suits it, a span that takes in most ordinary garden ground.
Temperature
This is a hardy grass at ease across a wide range, from a deep winter low of -20°F (-29°C) to summer highs near 100°F (38°C). It dies back over winter and rises again from the roots each spring.
Humidity
Everyday outdoor air is all it asks, so there is no level to tend. It takes average garden humidity in its stride.
Feeding
A single feed of balanced general-purpose fertilizer in spring is enough. There is no call to keep feeding through the season, since the grass keeps its own steady, moderate pace.
Pruning
Cut the whole clump to the ground in late winter, ahead of new growth. The one habit to hold to is lifting any all-green shoots the instant they show, since they signal a reversion to the invasive form.
Repotting
In a container, divide and refresh the clump every 2 to 3 years, or sooner if the roots fill the pot or the center starts to fade. Splitting it keeps the plant vigorous and the color true.
Size & spacing
Look for a clump around 12 to 18 inches (30 to 46 cm) tall spreading 12 to 24 inches (30 to 60 cm) wide. Allow each plant that much room so the mound can fill out without crowding its neighbors.
When to plant
Place Japanese blood grass in the garden in spring once the last frost has passed, and it settles into its setting over the first growing season. It rarely flowers in cultivation, so the display rests on foliage rather than bloom. Cut the clump to the ground in late winter, and fresh red growth rises as the season warms.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring after last frost
- Harvest: rarely flowers in cultivation
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Most of what unsettles this grass is either weak color or, more seriously, the plant slipping back toward its invasive green parent. Learn to read one from the other, because the first is an easy adjustment and the second calls for a swift response. Match what you see below and act while it still counts.
Green intruders rising in the crimson clump
Those forceful green shoots mark the plant reverting to cogongrass, the wild green form of the species and one of the most invasive grasses anywhere. Lift out every green shoot the moment it appears, rhizomes and all, then bag the material and send it to the bin. Skip the compost pile entirely, and keep returning to the spot, since the green growth ranges quickly beneath the soil.
Fix:
- Dig out the green-reverting shoots immediately, including rhizomes
- Bag and destroy all removed material; do not compost
- Monitor the area repeatedly for regrowth
Restricted or weed-listed in your area
Settle the legal question before this grass ever reaches your garden, because the species is a federal noxious weed that cannot be sold or moved across state lines, and many states bar even the ornamental form. In its cogongrass guise it forms dense, fire-prone stands that overtake native plantings. Review your state's rules ahead of planting or relocating it, keep clear of the southeastern US, and remove and destroy any plant growing where it is not permitted.
Fix:
- Verify local and state legality before planting or moving the plant
- Do not plant in or near the southeastern US
- Remove and destroy plants where prohibited
Washed-out color instead of deep red
Muted color almost always comes down to too little sun. The deepest blood-red belongs to a clump in full sun, while one set in heavy shade holds onto a duller green. Give it a brighter, sunnier position, keep the soil evenly moist, and the rich tone finds its way back.
Fix:
- Relocate to a site with full sun for best red color
- Ensure soil stays evenly moist
Toxicity
The reassuring note first: Japanese blood grass is not poisonous to people or pets, and the ASPCA leaves it off its toxic-plant lists. A curious cat or dog may bring up a little grass after a nibble, and that is all. The real concern is not poison but how readily this grass turns invasive, so read the section above on reversion and state law.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A household cat is safe alongside it. A chewed blade might prompt a little grass to come back up, which is the ordinary response to any greenery rather than poisoning.
Dogs None
Dogs share the same clean bill. The most a curious mouthful tends to bring is a spell of mild, passing stomach upset.
Horses None
Horses are in no danger, since the foliage lacks the toxins that trouble them in so many garden ornamentals.
Rabbits None
Rabbits may graze the blades without concern, because none of the plant is toxic to them.
Livestock None
Cattle, goats, and sheep run no risk of poisoning from the leaves.
Birds None
Birds come to no harm near it, with nothing poisonous in either the leaves or the seed.
People None
It is safe to handle and to keep in a home with children. No one grows it for the table, and the single thing to note is pollen, which may bother anyone inclined to hay fever.
Not chemically poisonous; pets that nibble grass may vomit or have mild stomach upset, and grass pollen can affect allergy-prone individuals. The real risk with this plant is invasiveness and legality, not toxicity.
Varieties
Two forms are worth knowing, and the difference between them tells the entire story of this plant.
Red Baron
This is the ornamental form that lands in gardens, its upright slender blades coloring blood-red from the tips down and seeming to ignite when low sun passes through them from behind.
Imperata cylindrica (species, cogongrass)
The all-green wild form holds federal noxious weed status and counts among the most damaging grasses on earth, raising dense fire-prone stands, and the red cultivar can lapse back into it.
How to propagate
This grass increases by one means, dividing the clump, and the task stays simple as long as you keep watch for any green-reverting growth.
DivisionEasy
Spring · One growing season
Dividing the clump in spring is the single route to more plants, since this cultivar seldom sets seed worth sowing. Lift an established clump, part it into sections, and settle them back in, and each piece finds its footing across one growing season. Set aside any division showing green reverting growth for disposal rather than passing it along.
Myths
This crimson ornamental is entirely safe and altogether carefree.
The red form is truly non-toxic to pets, so that reassurance stands. The complication lies elsewhere: it can revert to the aggressive green cogongrass, the species itself is a federal noxious weed, and its sale is banned or restricted across many states. The concern that matters is invasiveness and legality, not poison.