galinsoga
Galinsoga parviflora
Asteraceae
Comments: This is an upright annual weed that is occasionally found in crops and gardens. It is not as common throughout New Zealand as other cropping weeds such as fathen, but in some places can be common enough to be troublesome. It is an annual weed, normally germinating in spring, but also able to germinate in autumn.
Distinguishing Features: It tends not to grow quite as tall as some upright annual weeds found in crops such as fathen and redroot. Note that the stems aren't always as straggly as shown in the top picture. The leaves are not particularly distinctive, looking similar to a number of other common weed species. Being a member of the Asteraceae family, the flowers are similar to those in weeds such as daisy and stinking mayweed, with central yellow disk florets surrounded by white ray florets (often incorrectly called petals). However, unlike daisy and stinking mayweed, the ray florets of galinsoga are very small, and so the flowers are not as noticeable as in some of these other Asteraceae species.
Control: As with many annual weed species, there are usually no particular problems with controlling galinsoga, with it being susceptible to most selective herbicides and also cultivation. It is poorly controlled by trifluralin.