Johnsongrass
Sorghum halepense · Poaceae
The gardener's calendar
Ideal time to plant johnsongrass: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Family
- Poaceae (grasses)
- Type
- Perennial herbaceous grass
- Mature height
- 60 to 150 cm
- Growth
- Very rapid
- Hardiness
- Hardy, tolerates moderate frosts
- Flowering
- Summer to autumn (July-October)
- Foliage
- Deciduous, senescent in winter
- Origin
- Near East and North Africa
Care
Exposure
Johnson grass thrives in full sun, exposed to at least 6 hours of direct light daily. Maximum exposure promotes vigorous growth and flower production. It tolerates partial light shade but develops less densely in such conditions.
Soil
This grass adapts to most soils, including poor, dry, or chalky ones. Proper drainage remains essential to prevent root asphyxia. Well-drained soil, even light soil, is sufficient for optimal development.
Watering
Once established, Johnson grass tolerates drought very well thanks to its deep root system. Water regularly during the first growing season. Under normal conditions, rainwater is sufficient; intervene only during prolonged heat waves.
Fertilizing
No fertilizer is strictly necessary on average soils. On very poor soils, a balanced fertilizer application in spring can support growth. Favor moderate application rather than excessive feeding.
Pruning and cutting
No pruning is strictly necessary. You can cut back faded stems in late autumn or early winter for aesthetics. Allow natural self-seeding or eliminate unwanted young plants by pulling them out before they become deeply rooted.
Pests and diseases
Johnson grass is generally robust. In very humid and waterlogged conditions, root rot may appear. Excess moisture and poor aeration promote fungal problems; therefore prioritize good drainage and airy planting density.
Did you know?
Johnson grass (Sorghum halepense) is a grass native to the Near East that bears the name of the historic city of Aleppo (Halab). Long used as a forage plant in Mediterranean zones, it has naturalized in many temperate and subtropical regions, where it rapidly colonizes abandoned or disturbed land thanks to its aggressive rhizomes.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
- Tufted hair grassDeschampsia cespitosa
- Wavy hair-grassAvenella flexuosa
- Purple moor-grassMolinia caerulea
- Reed canary-grassPhalaris arundinacea
- Common quaking grassBriza media
- Creeping soft-grassHolcus mollis
Tips generated and checked by Viridia — adapt them to your local climate.