General Plant Information (Edit)
Plant Habit: Grass/Grass-like
Life cycle: Perennial
Sun Requirements: Full Sun
Water Preferences: Mesic
Dry Mesic
Dry
Soil pH Preferences: Strongly acid (5.1 – 5.5)
Moderately acid (5.6 – 6.0)
Slightly acid (6.1 – 6.5)
Neutral (6.6 – 7.3)
Slightly alkaline (7.4 – 7.8)
Minimum cold hardiness: Zone 2 -45.6 °C (-50 °F) to -42.8 °C (-45°F)
Maximum recommended zone: Zone 11
Plant Height: 1 to 8 feet
Fruit: Showy
Other: Panicles of purplish seed heads containing shiny, oval reddish brown seeds.
Fruiting Time: Late summer or early fall
Fall
Bloom Size: Under 1"
Flower Time: Summer
Late summer or early fall
Underground structures: Rhizome
Uses: Erosion control
Will Naturalize
Wildlife Attractant: Butterflies
Resistances: Humidity tolerant
Drought tolerant
Pollinators: Wind

Image
Common names
  • Johnsongrass
  • Johnson Grass

Photo Gallery
Location: Reading, Pennsylvania
Date: 2023-09-14
view of grass seedheads in panicle clusters
Location: N. E. Medina Co., Texas
Date: June 2012
Johnson Grass in bloom
Photo by PromiselandFarm
Location: Reading, Pennsylvania
Date: 2023-09-14
big patch off of bicycle-hiking trail
Location: Reading, Pennsylvania
Date: 2023-09-14
broad blades with a white vein down middle
Photo by SongofJoy
Photo by SongofJoy
Comments:
  • Posted by ILPARW (southeast Pennsylvania - Zone 6b) on Dec 30, 2023 1:38 PM concerning plant:
    This grass species is native to the Mediterranean Region and got its name of Johnsongrass from a certain Colonel William Johnson who introduced the grass to his river-bottom farm in Alabama in 1840. It has become invasive and spread to all lower 48 states of the USA. On the one hand, it is considered a noxious weed in farm fields for corn, soybeans, and other crops; however, it is also considered as a good forage grass for livestock that is quite edible for animals until after it blooms. It is similar in appearance to Switchgrass, Redtop, and Purpletop but differs in being taller, having not just fibrous roots but also white to brown rhizomes (underground stems), and the broad blades bear a conspicuous white vein down the middle. The egg-shaped seeds turn from green to greenish violet, to dark reddish brown and are not as nicely reddish or purplish as Redtop or Purpletop respectively.

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