Galinsoga

Galinsoga 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, such as in nurseries and gardens.

It is an annual weed, normally germinating in spring, but also able to germinate in autumn.

It tends not to grow quite as tall as some upright annual weeds found in crops such as fathen and redroot. 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 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, so the flowers are not as noticeable as in some of these other Asteraceae species, but very distinctive if you do notice them. There are only five ray florets (white “petals”) per flower. 

There are two main types of galinsoga in New Zealand. In some areas, you’ll find mainly the Galinsoga parviflora shown. In other areas, it is Galinsoga quadriradiata that is more common. This tends to have slightly more jagged leaf margins than the Galinsoga parviflora, and the foliage is usually a bit more hairy. Both are simply known as galinsoga in New Zealand.

As with many annual weed species, there are usually no particular problems with controlling galinsoga, with it being susceptible to cultivation and most selective herbicides such as atrazine, oxadiazon, glufosinate, terbuthylazine, metribuzin, methbenzthiazuron and mesotrione.

It is poorly controlled by trifluralin and ethofumesate, and needs to be treated at the seedling stage with herbicides such as clopyralid, bentazone and bromoxynil.