Hairy Galinsoga - Weed of the Week

A Gardener’s Constant Menace

Hairy galinsoga ( Galinsoga quadriradiata), sometimes referred to as shaggy soldier, is a weed that the constant gardener loves to hate. It is a summer annual that belongs to the sunflower family ( Asteraceae) and can often invade vegetable gardens to establish dense infestations by crowding out other plant species. Certain traits, such as rapid seedling development, ability to bloom following a short period of vegetative growth and producing multiple generations during a growing season, help hairy galinsoga establish swiftly in gardens.

It also can occur in disturbed sites and cropping fields and is known to serve as an alternate host for certain nematodes and more than 20 insect pests. Hairy galinsoga is considered to have originated in Central to South America, but it has become naturalized in North America and other temperate and tropical regions. This weed is not usually found in lawns.

Hairy galinsoga is considered to be edible and to possess other beneficial attributes. It can be consumed by both humans and livestock. Young leaves can be used in a soup or in dishes, such as risotto and lasagna. Due to the presence of certain secondary metabolites, such as flavonoids and phenolic compounds, it has been documented to have antioxidant and anti-inflammatory properties. Extracts from hairy galinsoga are known to coagulate blood and have been used to treat wounds. Certain beneficial insects, such as hoverflies, are attracted by its flowers.

Hairy Galinsoga Identification

Hairy galinsoga, as inferred from its name, is characterized by profuse hairs on stems and leaves. This trait distinguishes it from its cousin, gallant soldier ( Galinsoga parvifolia), which has similar morphological characteristics, except for limited to no hairiness and narrower leaves. Leaves are oval with serrated margins and are arranged oppositely on the stems with distinct petioles. Its flowers have densely packed disc florets that are yellow in color and five tiny white ray florets, each with three crenate teeth at the tip. Seeds of hairy galinsoga germinate between 12°C (54°F) and 30°C (86°F) with an optimum temperature requirement between 20°C (68°F) and 24°C (75°F); most of the seed germination occurs from May to June. It produces flowers prolifically from about mid-June until late fall. Fallen seeds can germinate immediately due to the absence of dormancy requirement. This phenomenon may be exploited to eradicate hairy galinsoga from an infested field by thoroughly managing it for three to four years.

Controls for Hairy Galinsoga

Mechanical methods, such as hoeing or cultivation, are effective if carried out repeatedly during the earlier stages of weed growth. Mulches, such as thick (6-mil) black plastic or straw over newspaper, are effective to control this weed in home gardens but will have to be applied prior to germination. In vegetables, such as tomato, pepper, potato and sweet corn, the herbicide metolachlor (Dual II Magnum) when applied prior to weed germination followed by late-season cultivation has been found to provide effective control. In landscapes and nurseries, pre-emergent herbicide indaziflam (Specticle G) controls this weed. In non-crop situations, the herbicide 2,4-D or glyphosate can effectively control this weed when applied during its early stages.

Author:  Rakesh Chandran, WVU Extension Weed Science Specialist  
Last Reviewed: August 2020 

Recommendations for the use of agricultural chemicals are included as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services does not imply endorsement by West Virginia University Extension Service nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.