Ox-eye Daisy, Leucanthemum vulgare

A large patch of ox-eye daisy.

A large patch of ox-eye daisy.

From late spring into summer, pretty white daisies dance on the ends of long stems in gardens, meadows, dry fields, roadsides and railroad right-of-ways and even waste areas. Ox-eye daisy, Leucanthemum vulgare (= Chrysanthemum leucanthemum), is an attractive, but somewhat weedy, short-lived herbaceous perennial from the British Isles, Europe and northern Asia. Hardy in zones 3-9, it is now naturalized throughout the US and southern Canada. The showy flowers make this a popular garden plant.  It is often confused with the ornamental Shasta daisy (L. x superbum or C. maximum) but that plant is more robust and has larger flowers that bloom later on heavier stems. Scentless chamomile (Matricaria maritima) is another similar plant but it is an annual that has smaller flowers and much more finely dissected leaves.

Ox-eye daisy in full bloom.

Ox-eye daisy in full bloom.

Also known as marguerite, field daisy, white daisy, moon daisy, moon-penny, dog daisy, and many other common names, this plant in the family Asteraceae (Compositae) was introduced to North America a long time ago and has become naturalized in a variety of plant communities, displacing native plant species in some areas. It is not a threat to intact prairies and savannas but readily invades disturbed ground. In some places it is considered a noxious weed and is especially problematic in pastures and western rangeland, becoming a greater problem as grazing intensity increases in wet summers. Although not poisonous, cattle and deer avoid it. Sheep, goats and horses will eat it but it can impart an off-flavor to the milk of animals that consume it. Populations in some areas have become resistant to many herbicides. Seeds can remain viable after passing through the digestive tract of cattle, so care should be taken when moving stock to avoid spreading the seeds. This species can also harbor the plant disease aster yellows and several nematode species.  Ox-eye daisy can also invade turfgrass, becoming a lawn weed that tolerates mowing. It is often included in wildflower seed mixes.

Ox-eye daisy readily self-seeds, producing many seedlings.

Ox-eye daisy readily self-seeds, producing many seedlings.

With no dormancy requirements, seed can germinate throughout the growing season, although most seedlings establish in the fall. Seedlings have smooth leaves that are dull above and pale beneath, with shiny veins and dark green splotches between the veins. Seedling growth is slow the following spring (and through that winter in mild climates), with the crown and rhizomes developing from the fibrous root system during the summer. New shoots emerge from the crown in the fall and the plant flowers during its second year.

Ox-eye daisy can be a weed in lawns.

Ox-eye daisy can be a weed in lawns.

This species initially develops as a basal rosette, forming clumps 1-2 feet tall and wide. The alternate, glossy, dark green leaves are coarsely toothed to pinnately lobed. These basal and lower leaves are ovate to spoon-shaped and typically about 4” long. The rosettes are evergreen except in the harshest climates. The short-lived plants will produce stems from the root crown or laterally creeping rhizomes. The prostrate basal stems can produce adventitious roots. The entire plant produces a somewhat disagreeable odor when cut or crushed.

Terminal flowers are borne on the end of stems that extend 1-2 feet above the foliage. The profuse flower stems are sometimes branched but usually are single, with a few small, sessile leaves that decrease in size from bottom to top. The solitary daisy flower heads are 1-3” inches across with about 20-30 white ray florets surrounding the yellow disc florets. The white “petals’ are slightly notched at the tips. The flowers are pollinated primarily by insects, including beetles, flies, wasps and butterflies. Plants bloom in mid-spring but if deadheaded will continue to produce flushes of flowers throughout the summer. The plants produce abundant, brown or black flat, ribbed seeds (technically a dry, indehiscent achene lacking a pappus). A single plant typically produces 1,300-4,000 seeds but many more (up to 26,000) may occur on particularly vigorous plants.

The solitary flowers open from tight buds (L), with characteristic white ray florets surrounding the yellow disc florets (C and R).

The solitary flowers open from tight buds (L), with characteristic white ray florets surrounding the yellow disc florets (C and R).

Ox-eye daisy prefers heavy, moist soils but tolerates a wide range of conditions. It is considered difficult to control or eradicate because the plants can grow from rhizome fragments and it self-seeds vigorously in open habitats.

Ox-eye daisy can form dense colonies.

Ox-eye daisy can form dense colonies.

It is easily controlled by continued cultivation but not by mowing. Unwanted seedlings are easily removed in the garden. However this species does aggressively invade fields, where it forms dense populations, thus decreasing plant species diversity, so even garden plantings should be deadheaded when flowers begin to fade to help reduce the amount of seed produced. Seed can remain viable in the soil for many years, although most of the seed germinates soon after it is dropped from the flowers or the following spring. Seed germinates readily on bare soil; mulching after seeds are shed will reduce seedling populations in garden situations.

– Susan Mahr, University of Wisconsin – Madison