How does hypericum spread?
Spreads rapidly by underground stems and can spread aggressively in ideal growing conditions. Plant 18" apart for use as a ground cover.
Specialist journal
Spreads rapidly by underground stems and can spread aggressively in ideal growing conditions. Plant 18" apart for use as a ground cover.
Considering that this plant is so invasive, consider growing St. John's wort in a container, where its spreading roots and abundant seeds can be kept in check. This plant is easily established in areas where soil is moist but well-drained and in full sun to part shade.
One species of Hypericum – Hypericum perforatum – is listed as a noxious weed in this state by the California Invasive Plant Council. … It is also known as Klamath weed because it invades pastures and roadsides of northern California and Oregon. The plant causes animals that eat it to be highly sensitive to sunlight.
It appears this plant is invasive on the West Coast, but it works great on the East Coast. … It appears there is a native hypericum (prolificum), and an Asian- European invasive species (calycinum) that needs to be avoided at all costs.
John's Wort spreads easily, and a single plant can produce up to 100,000 seeds per year. Those seeds can be viable for up to ten years.
Hand pulling or digging St. John's-Wort before the flowers go to seed can reduce the spread of this plant. Remove as much of the root system as possible to help prevent regrowth.
John's wort (Hypericum densiflorum) is a native shrub that can grow up to 6' tall with a spread of 3-6' wide.
St. John's wort (SJW), known botanically as Hypericum perforatum, is a sprawling, leafy herb that grows in open, disturbed areas throughout much of the world's temperate regions.