Skaneateles Conservation Area/Invasive species/Centaurea jacea s.l.

Centaurea jacea s.l.
The Centaurea jacea complex includes the following knapweed species:
 * Centaurea jacea (brown knapweed),
 * Centaurea nigra (black knapweed),
 * Centaurea nigrescens (tyrol knapweed),
 * Centaurea × moncktonii [C. jacea × C. nigra] (meadow knapweed).

These taxa can be difficult to differentiate, and all are known to hybridize with one another.

It is clear that one or more of these species are present and indeed widespread at the Skaneateles Conservation Area (SCA).

Ecological impact
The Centaurea species in this group can increase the density in the herb layer and larger stands clearly reduce the number of individual native plants.

Biological characteristics and dispersal ability
The Centaurea species in this group are perennial plants that can produce hundreds or up to a thousand seeds on a single plant. The seeds are small, light and flat. Dispersal could be passive (wind) or active (animal). Seed can be spread in contaminated hay or seed mixtures and by mowing equipment.

Ecological amplitude and distribution
Suitable habitats for the Centaurea species in this group include cultivated uplands, grasslands, old fields, forests, woodlands, and roadsides, all of which are present at the SCA. Large stands at and around the SCA have been noted with both native and other invasive species already present.

The native range of these knapweeds (Europe) contains climate similar to that of Central New York. They are present in all northeastern states and provinces and in all New York State PRISMS.

Difficulty of control
Seeds are assumed to remain viable for at least a year, unlikely up to 10 years.

Regrowth of these knapweeds is from ground-level meristems rather than from extensive underground root systems, but plants can still be difficult to pull up dig. Multiple herbicide treatment may be required to eradicate stands.