Malta starthistle

Centaurea melitensis full plant — Full plant

Max Lichter

Common Name(s)

Malta starthistle

Napa starthistle

Tocalote

Scientific Name

Centaurea melitensis

Family

Sunflower or Aster family (Asteraceae)

Reasons for concern

Malta starthistle is an adaptable, quick growing plant that outcompetes native species. It is also toxic to horses.

Classification

Non-native

Botanical description

Bushy annual rosette with a tall, branching wiry stems

Leaves

Young plant is a lobed basal rosette. 1-5 inch long oblong leaves, with larger lower leaves having lobed margins. Most leaves have small, prickly hairs

Stem(s)

Up to 3 feet tall branching stems covered with gray prickly hairs

Flowers

Spiny, yellow disked flowers comprise the flower head and look similar to Yellow starthistle. The base is ½ - 2 inches wide, egg shaped, and covered in cobweb-like hairs. The bract below is brownish purple with brownish purple spines.

Fruit

Dry, light brown cypselae with white or light brown hairs

Roots

Deep taproot

Native to

Mediterranean

Where it grows

Disturbed areas like roadsides, lots, pastures, and open fields.

Lifecycle

Annual

Reproduction

By seed

Weedy Characteristics

Malta starthistle prolifically produces seeds that can remain dormant underground for up to 3 years. These seeds can be spread by wind, water, animals, or people. The plant can adapt to a wide variety of environmental conditions, making it outcompete native plants

Look-alike Plants

Desert thistle (Cirsium neomexicanum) can be distinguished by its wider, flatter white to purple flower and thinner stems and leaves. The base of the flower is also flatter and wider.

Control Strategies

Hand pulling is very effective, but when the plant is seeding, it can be bagged and removed to make sure new plants dont grow. Herbicides like 2-4 D, aminopyralid, transline, dicamba, and glyphosate should be applied before flowering.

Gallery

References