Both species are sometimes known locally as ‘carrot weed’.
The two species have similar feathery, fern-like leaves and small white flowers arranged in umbels (the stalks of individual flowers are arranged rather like the spokes of an umbrella arising from the same point on the end of the flowering stem)
The leaves of Daucus carota are finer than those of Oenanthe pimpinelloides and are divided three times rather than just twice into ovate or linear segments. The final segments of Daucus carota are linear or lobed or have serrate edges
When crushed the leaves of Daucus carota have a distinctive ‘carroty’ smell
In Oenanthe pimpinelloides the young plants have leaves about 10 cm long, divided into opposite leaflets. As the plants grow older the leaves become much larger and are twice divided
Individual flowers are up to 7 mm in diameter in Daucus carota, and up to 4 mm across in Oenanthe pimpinelloides. The whole umbel is larger in Daucus carota (up tō 12 cm in diameter) than in Oenanthe pimpinelloides (2-6 cm in diameter). In Daucus there is a ring of green pinnate bracts (in appearance like small, narrow leaves with linear segments) just under the umbel and sometimes the flowers at the centre of the umbel are pink
Daucus carota has a slender white taproot smelling strongly carrot: Oenanthe pimpinelloides has fibrous roots with conspicuous black tubers
After flowering, the umbel of Daucus carota closes up, with the individual rays curling upwards
Fruits of Daucus carota are spiny and can cling to fur or clothing: this distinguishes them from other species.
Biology
Origin
Daucus carota is native to Europe, Asia and North Africa: Oenanthe pimpinelloides originated in Europe and Asia Minor
The cultivated carrot (sometimes classified as Daucus carota subsp. sativus) was developed from the wild carrot, probably in ancient Persia, over 2000 years ago
The first domesticated carrots in New Zealand were planted by Captain Cook in Queen Charlotte Sound in 1773
Domesticated carrot may revert to wild carrot quite quickly
New Zealand produces 80% of the world’s carrot seed
Oenanthe pimpinelloides was first recorded in New Zealand in 1940.
Life cycle
Daucus carota is an annual or biennial whereas Oenanthe pimpinelloides is a perennial, regrowing from the base every year
Seed of wild carrot is dormant when fresh and must experience a period of after-ripening before it can germinate. After this process it can germinate at any time of the year when soil moisture is adequate. Like many other weeds germination tends to occur in separate flushes
Wild carrot sends up flowering shoots between August and May: parsley dropwort between October and April.
Benefits
Wild carrot is and has in the past been used as an aromatic herb with a number of claimed medicinal properties. Amongst other things it has been used as a diuretic, to sooth the digestive tract and to stimulate the uterus
Wild carrot is readily eaten by sheep, even when flowering
Carrots can be a useful companion plant for tomatoes and may also provide a good microclimate for lettuce.
Occurrence
Wild carrot grows throughout the North Island, and in some places can be abundant. In the South Island it is most commonly found in western and southern areas, on roadsides and in some pastures in late spring and early summer. It can be abundant on dry, open, hill slopes.
Parsley dropwort is found in grazed pasture, on disturbed ground, playing fields, parks, lawns and gardens especially in Northland, but is increasing in parts of the Waikato, Coromandel and East Coast of the North Island. Generally, parsley dropwort grows in a damper environment than wild carrot.
Impacts
Impacts on pasture
Both species replace more useful pasture species
When flowering wild carrot is less palatable to cattle but is still readily eaten by sheep
Parsley dropwort is not palatable to livestock and becomes even less so when its flowering stems become woody
Hay from pastures infested with parsley dropwort is worth less and probably helps spread the weed.
Impacts on livestock
Cattle tend to ignore wild carrot when it is flowering but it has been reported to taint milk
Parsley dropwort is considered poisonous in South Australia, and it has several close relatives which are poisonous to livestock.
Control
Little research has been carried out on control of parsley dropwort
However, 2,4-D ester at rates of 3 litres per ha in June or August (before restrictions on its use begin in September in Northland) seems to give reasonable control and MCPA seems almost equally effective
In waste areas glyphosate or metsulfuron-methyl are effective
Wild carrot is controlled by 2,4-D or MCPA in the seedling stage but can be harder to control when it gets older.
Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.