Is Johnsongrass good for gardens?

No, it is highly invasive and will quickly outcompete most garden plants.

How do I get rid of it?

Consistent digging to remove all rhizomes or repeated mowing is required to weaken the plant.

Plant guide

Johnsongrass.

Sorghum halepense

Pronounced SOR-gum ha-leh-PEN-see

Also known as Aleppo Grass, Arabian-millet, Columbus Grass, Cuba-grass, Egyptian Millet, Evergreen Millet, Grass Sorghum, Great Millet, Johnson Grass

Johnsongrass is a resilient perennial grass that spreads through seeds and underground rhizomes. It is often considered an invasive weed in many parts of the world due to its aggressive growth habit. You will find it thriving in open fields, roadsides, and disturbed soils.

At a glance

Care level: Easy
Plant type: Perennial grass
Light: Full sun
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: 7 feet
Growth rate: Fast
Hardiness: USDA 6 to 10
Bloom time: Mid to late summer

Care

This grass is extremely hardy and requires very little attention to survive. Watch for rapid spread, as its rhizomes can quickly take over garden beds. It prefers full sun and well drained soil to reach its full height.

Watering: It is quite drought tolerant once established but grows best with consistent moisture.
Feeding: It rarely needs extra food, but a light application of balanced fertilizer in spring can boost growth.
Pruning: Cut back regularly if you want to prevent it from going to seed and spreading.
Repotting: If kept in a container, move it to a larger pot when the roots become crowded.
Soil: Well drained, fertile soil
Soil pH: 5.0 to 7.5
Temperature: -15 to 40°C
Humidity: 30 to 80%

Safety

People: The plant is considered toxic due to the presence of hydrocyanic acid, especially in young or stressed growth.
Pets: This plant can be toxic to livestock and pets if it contains high levels of cyanogenic glycosides, especially after frost or drought.
Children: Keep children away from this plant as the sharp leaf edges can cause cuts and the foliage is toxic if ingested.
Contact allergens: The leaves have sharp, serrated edges that can cause mechanical skin irritation.
Airborne allergens: The pollen is a significant airborne allergen for many people during the late summer flowering period.
Edibility: The foliage can contain cyanogenic glycosides that release cyanide when damaged, making it toxic to livestock and potentially dangerous if ingested by humans.

How to identify it

Tall stems reaching 2 to 7 feet
Long, flat, lance shaped leaves
Prominent white midrib on leaves
Large, open, purplish flower panicles

Height: 0.5 to 2.5m
Spread: 0.3 to 1m
Leaves: green, deciduous
Flowers: purple, green, 0.5 to 1cm
Fruit: brown, Autumn

Problems to watch for

Rust · Fungal infection causing orange or brown pustules on the leaves.

By symptom

Plant problems by symptom

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Growing it

Propagation: division, seed
When to plant: spring

There are no recommended companions for this species as it is an aggressive weed that should be managed for removal.

Similar species

Sorghum · It is a related cultivated crop that lacks the aggressive, invasive rhizome system of Johnsongrass.

Science

Family: Poaceae
Genus: Sorghum
Order: Poales
Class: Liliopsida
Native range: Mediterranean region and parts of Asia.
Conservation: It is classified as a noxious weed in many regions and should not be planted intentionally.

It thrives in disturbed soils and open fields, spreading rapidly through an extensive underground network of rhizomes.

Value to wildlife: seed source for birds, nesting material
Pollinators: bees, butterflies
Uses: erosion control, wildlife habitat

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 3/9
Soil reaction: 6/9
Light: 8/9
Temperature: 6/9
Moisture: 5/9
Nutrients: 7/9

Taxonomy resolved against GBIF.

Questions people ask

Is Johnsongrass good for gardens?: No, it is highly invasive and will quickly outcompete most garden plants.
How do I get rid of it?: Consistent digging to remove all rhizomes or repeated mowing is required to weaken the plant.

Where the name comes from

The common name honors William Johnson, who introduced the grass to his Alabama farm in the 1830s. The scientific name refers to the Aleppo region in Syria.

Good to know

It was introduced to the United States in the 1800s as a potential forage crop.
A single plant can produce thousands of seeds in one season.
The rhizomes can grow several feet deep into the soil.

Also in

Plants toxic to cats and dogs

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This guide was generated with AI on October 19, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.