Galinsogas
Hairy galinsoga, Galinsoga quadriradiata Cav. = G. ciliata (Raf.) S.F. Blake
Smallflower galinsoga, Galinsoga parviflora Cav.



Images above: Upper Left: Hairy galinsoga seedling (Scott Morris, Cornell University). Upper Right: Hairy galinsoga mature plant (Scott Morris, Cornell University). Bottom: Hairy galinsoga flower (Scott Morris, Cornell University).


Images above: Left: Smallflower galinsoga plant (Joseph DiTomaso, University of California, Davis). Right: Smallflower galinsoga seed head (Joseph DiTomaso, University of California, Davis).
Identification
Other common names:
- Hairy galinsoga: French-weed, common quickweed, shaggy soldier, ciliate galinsoga, fringed quickweed, quickweed, Peruvian daisy, shaggy galinsoga
- Smallflower galinsoga: gallant soldier
Family: aster family, Asteraceae
Habit: Highly branched, summer annual herbs.
Description: Seedlings have 0.4” (1 cm) long, stalked cotyledons and opposite young leaves.
- Hairy galinsoga: Cotyledons are hairless and square or egg shaped, with flattened, slightly indented tips. Seedling stems are short, green and sometimes turn maroon with time. Young leaves are triangular or egg shaped and light green, with a pointed tip. Three prominent veins are red tinged above and hairy below. Dense hairs are present on the stem, stalks, toothed leaf edges, and upper leaf surface, hairs located on leaf edges point toward the leaf tip.
- Smallflower galinsoga: Cotyledons are round to lima bean shaped, with indented tips and a fringe of tiny hairs along the margin. Young leaves are paddle to broadly oval shaped, slightly cupped, and sometimes toothed, with a tapered tip. Very young leaves are grooved along one to three veins.
Mature plants are upright and much-branched. Branching occurs in even pairs from axils of the opposite leaves.
- Hairy galinsoga: Densely hairy stems reach 4-28” (10-70 cm) in height. Coarse hairs are present on leaf stalks, the entire upper leaf surface and veins on the lower leaf surface. The broad leaves are 1-3” (2.5-7.5 cm) long by 0.5-2” (1.3-5 cm) wide, egg-shaped to triangular, with coarsely toothed, hairy edges. Roots are shallow and fibrous.
- Smallflower galinsoga: Irregularly hairy stems are 12-24” (30-60 cm) tall. Hairs are concentrated near stem-leaf joints and on leaf stalks. Leaf stalks are 0.5” (1.3 cm) long, thin, and may be absent on younger leaves. Leaves are egg-shaped to lance-egg-shaped with a pointed tip, 0.3-4.25” (0.8-11 cm) long by 0.1-2.75” (0.3-7 cm) wide, light green, and finely to coarsely toothed. A small taproot may be present.
Flower heads of both species are clustered at branch ends; they have 4-5 small, usually white, 0.1” (0.25 cm) long ray flowers. Petals have 3 rounded teeth at their tip. The center of the flower head is a mounded group of distinct yellow disk flowers that each produce one seed.
- Hairy galinsoga: Flower heads are 0.25” (0.6 cm) in diameter, with occasional pink petals. Petaled ray flowers do not produce seeds.
- Smallflower galinsoga: Flower heads are 0.13” (0.3 cm) in diameter. Petals are only white and the petaled ray flowers produce seeds. There are 15 to 50 yellow disk flowers per ray flower.
Fruit and seeds: The apparent seeds are covered with a tight hairy coating of fruit tissue. These four-sided seeds are topped with a crown of papery brown scales.
- Hairy galinsoga: Seeds are 0.1” (0.25 cm) long, and torpedo shaped.
- Smallflower galinsoga: Seeds are 0.06” (0.15 cm) long, and cylinder or oval shaped. Slightly wedged seeds are derived from the ray flowers.
Similar species: Seedlings can be confused for Virginia copperleaf (Acalypha virginica L.), but the two can be distinguished by looking for the notched, not broadly indented, tip of the Virginia copperleaf cotyledon. Unlike Galinsoga spp., all but the first true leaves of Virginia copperleaf are alternate.
Management
Hairy and smallflower galinsoga are particularly prominent in low-growing vegetable and specialty crops (De Cauwer et al. 2019, Warwick and Sweet 1983). Since their seeds do not persist for more than a couple of years in the soil, one of the best tactics for managing these weeds is to rotate fields into a sod crop periodically. Three or four years in sod is usually sufficient to nearly or completely eradicate an infestation (Warwick and Sweet 1983). Reduction of the population will be more complete if galinsoga is prevented from seeding during the establishment of the sod, for example, by use of a nurse crop or mowing. A few years of aggressive control to avoid seed production can greatly reduce populations. For example, a competitive summer annual cover crop can reduce galinsoga seed production by more than 98% (Kumar et al. 2009). After the seedbank has been depleted, avoid reintroducing galinsoga in soil clinging to shoes and machinery.
Controlling the galinsogas requires continual attentionto field conditions. Avoid building excessive levels of soil phosphorus from manure or compost amendments as this will favor galinsoga growth and reproduction more than that of crops such as lettuce with modest fertility requirements (DiTommaso et al. 2022). Because these species go to seed so rapidly, clean up fields immediately after harvest to reduce population growth. During summer fallow periods, either keep the soil clean cultivated at 3 to 4 week intervals to flush out seedlings, or plant with a competitive cover crop. If time and the season permit, try to work in a cultivated fallow period before planting. Since the seeds can only emerge from the top 0.4” (1 cm) of soil, a thorough cultivation at shallow depth can effectively deplete the surface seedbank without bringing up new seeds. A false seedbed with flame weeding reduced hairy galinsoga plant density more than shallow tillage, however tillage to 0.8-1.6” (2-4 cm) depth provided the highest seedbank reduction (De Cauwer et al. 2019).
Two alternatives are available for handling very heavy seedings that result from an occasional year with poor control. First, since the seeds mostly germinate near the soil surface, do not till between seed production and when the first flowers appear on spring germinating plants. Most of the seeds will have germinated by then and will be destroyed when a seedbed is prepared for an early summer crop. Second, moldboard plow the seeds under as deeply as you can. For the next few years use relatively shallow tillage while the deeply buried seeds die off.
Ecology
Origin and distribution: Both species originated in Central America (Warwick and Sweet 1983). Both species occur in moist areas of the United States, primarily in the Northeast and northern states of the Midwest, with scattered occurrence in other humid parts of the United States (USDA Plants). Both species are widespread in temperate and tropical North and South America and have been introduced into various parts of Europe, Asia, Africa and Australia (Warwick and Sweet 1983). They are rare in dry regions of the world, even in irrigated crops.
Seed weight: Hairy galinsoga 0.18 mg, smallflower galinsoga 0.17 (Mohler unpublished); hairy galinsoga 0.23 mg, smallfower galinsoga 0.26-0.27 mg (Rai and Tripathi 1983, 1986); hairy galinsoga outdoor population 0.23 mg, greenhouse population 0.20 mg (Shantz and Shantz 1972).
Dormancy and germination: Freshly shed seeds of both species will germinate immediately if exposed to light and warm temperatures (Baskin and Baskin 1981, Ivany and Sweet 1973, Rai and Tripathi 1983, Warwick and Sweet 1983). However, seeds of hairy galinsoga shed in summer were dormant until late fall in the Czech Republic (Jursík et al. 2003) and some lots of smallflower galinsoga harvested in summer months were dormant (De Cauwer et al. 2014). Germination approaches 100% in light at a wide range of constant temperatures ranging from 54 to 97 °F (12 to 36 °C) or at fluctuating day/night temperatures ranging from 59/50 to 95/68 °F (15/10 to 35/20 °C), but decreases at cooler temperatures of 59/43 °F (15/6 °C) or lower (Baskin and Baskin 1981, De Cauwer et al. 2014, Jursík et al. 2003, Shontz and Shontz 1972). Both species show markedly reduced germination in the dark (Baskin and Baskin 1981, Rai and Tripathi 1987, Shontz and Shontz 1972, Warwick and Sweet 1983), which allows them to persist until the following season when buried in the soil. Nitrate has no effect on germination (De Cauwer et al. 2014).
Seed longevity: Studies of seed longevity are limited. In India, soil seed populations declined by more than 99% in cropland from winter to summer due to a combination of emergence and mortality (Rai and Tripathi 1984). In Mexico, viability of seeds from disk flowers of smallflower galinsoga declined by approximately 70% in the first year after burial, whereas those from ray flowers declined by approximately 50% (Espinosa-García et al. 2003). The general absence of galinsoga from farms where row crops are rotated with several years of sod indicates that few seeds survive in the soil for more than three years (Warwick and Sweet 1983).
Season of emergence: Emergence begins in early spring, peaks in late spring and early summer but continues until frost, particularly following soil disturbance (Ivany and Sweet 1973, Warwick and Sweet 1983).
Emergence depth: Only seeds at or very near the soil surface produce seedlings. Most galinsoga seeds produce seedlings when positioned on the soil surface, but only half emerge from 0.1” (0.2-0.3 cm), and none emerge from 0.4” (1 cm) (DeCauwer et al. 2014, Ivany and Sweet 1973, Sweet 1986).
Photosynthetic pathway: C3
Sensitivity to frost: Both species of galinsoga die when exposed to even mild frost (Warwick and Sweet 1983).
Drought tolerance: Both species are drought sensitive (Rai and Tripathi 1983). Hairy galinsoga is somewhat less sensitive to drought than tomato (Warwick and Sweet 1983, Sweet 1986).
Mycorrhiza: Smallflower and hairy galinsoga are mycorrhizal (Fracchia et al. 2009, Harley and Harley 1987).
Response to fertility: Both species thrive when N, P and K levels are all high, whereas, low levels of any of these nutrients will reduce growth and flowering (Rai and Tripathi 1987, Warwick and Sweet 1983). Following a corn crop, hairy galinsoga showed a much stronger response to P with no added N than to N with no added P (Garcia Freira 2014). Biomass and reproduction of this species increased most to increasing P at a high constant N level, but was relatively unresponsive to increasing N at constant P levels (DiTommaso et al. 2022). At reduced levels of N and K, smallflower galinsoga increases root growth, but hairy galinsoga does not (Warwick and Sweet 1983).
Soil physical requirements: Both species occur on a variety of soil types but prefer damp, rich soil (Warwick and Sweet 1983).
Response to shade: Both species grow best in full sunlight and show markedly reduced growth when shaded (Ivany and Sweet 1973, Shontz and Shontz 1972). Hairy galinsoga exhibits strong shade avoidance responses when grown in competition, including increased stem length and leaf area, delayed flowering and seed production, and greatly reduced biomass and seed production (Brainard, 2002).
Sensitivity to disturbance: Plants of all sizes usually wilt quickly when uprooted unless the weather is unusually wet. Stem fragments buried in moist soil can produce roots, thereby facilitating their persistence in cultivated vegetable crops (Damalas 2008, Sweet 1986, Warwick and Sweet 1983). Well-rooted plants tend to break near the base when pulled or hoed and then quickly regenerate (Mohler, personal observation).
Time from emergence to reproduction: Plants flower until the first killing frost (Baskin and Baskin 1981). Both species first flower 24-60 days after emergence (24-28 days determined by Ivany and Sweet 1973, 45 days observed by Doll 2002, and 41-60 days cited in Warwick and Sweet 1983). Flowering time of hairy galinsoga was delayed from 34 days in the absence of competition to 46 days with competion, but always occurred when there were 10 leaves on plants (Brainard, 2002). Seeds are released 8-14 days after flowering (Baskin and Baskin 1981, Ivany and Sweet 1973, Warwick and Sweet 1983).
Pollination: Both species readily self-pollinate, but are also cross pollinated by insects (Warwick and Sweet 1983).
Reproduction: Once a plant begins to flower, it will continue to grow and flower until frost (Ivany and Sweet 1973). Consequently, early emerging plants that are not killed by human intervention can produce many seeds. Medium sized plants of hairy galinsoga about 18” (45 cm) in diameter averaged 40,000 seeds/plant (Mohler, unpublished data). Plants grown in the absence of competition produced approximately 25,000 seeds within 67 days, whereas those grown under moderate competition within a broccoli crop produced no more than 4,000 seeds/plant during the same time period (Brainard, 2002). A plant of smallflower galinsoga in Japan produced 400,000 seeds (Warwick and Sweet 1983). Since plants mature rapidly and seeds can germinate immediately upon dispersal, both species are capable of completing three to four generations per year in the Northeast (Warwick and Sweet 1983, Sweet 1986).
Dispersal: Seeds disperse short distances by wind (Warwick and Sweet 1983), but the fine hairs attached to the seed are much reduced relative to most wind dispersed species in the aster (composite) family. The seeds are hairy and stick readily, but not persistently, to fur and clothing.
Common natural enemies: Both species are commonly attacked by a diversity of aphid and leafhopper species (Batra 1979). They are also susceptible to galinsoga mosaic virus (Behncken 1970).
Palatability: Leaves, stems, and flowers of hairy galinsoga are cooked in soups in Southern Mexico (Bautista-Cruz et al. 2011). Smallflower galinsoga contains high concentrations of protein and minerals and is consumed as a leafy vegetable in several areas of the world (Damalas 2008).
References:
- Baskin, J. M., and C. C. Baskin. 1981. Temperature relations of seed germination and ecological implications in Galinsoga parviflora and G. quadriradiata. Bartonia 48:12-18.
- Batra, S. W. T. 1979. Insects associated with weeds of the Northeastern United States: Quickweeds, Galinsoga ciliata and G. parviflora (Compositae). Environmental Entomology 8:1078-1082.
- Bautista-Cruz, A., M. R. Arnaud-Viñas, G. A. Martinez-Gutiérrez, P. S. Sanchez-Medina, and R. P. Pacheco. 2011. The traditional medicinal and food uses of four plants in Oaxaca, Mexico. Journal of Medicinal Plants Research 5:3404-3411.
- Behncken, G. M. 1970. Some properties of a virus from Galinsoga parviflora. Autralian Journal of Biological Science 23:497-501.
- Brainard, D.C. 2002. Weed management implications of a broccoli-winter rye intercropping system. PhD Dissertation. Department of Horticulture, Cornell University. 136 pp.
- De Cauwer, B., R. Devos, S. Claerhout, R. Bulcke, and D. Reheul. 2014. Seed dormancy, germination, emergence and seed longevity in Galinsoga parviflora and G. quadriradiata. Weed Research 54:38-47.
- De Cauwer, B., T. De Cuypere, S. De Ryck, L. Delanote, K. Dewaele, K. Willekens, and D. Reheul. 2019. Reduction in field emergence and seedbank density of Galinsoga quadriradiata and other weeds after contrasting false seedbed strategies in organic vegetable fields. Weed Research 59:265-278.
- Damalas, C. A. 2008. Distribution, biology, and agricultural importance of Galinsoga parviflora (Asteraceae). Weed Biology and Management 8:147-153.
- DiTommaso, A., C. L. Mohler, and A. S. Westbrook. 2022. Response of hairy galinsoga (Galinsoga quadriradiata) to nitrogen, phosphorus, and competition from lettuce. Weed Science 70:579–586.
- Doll, J. 2002. Knowing when to look for what: weed emergence and flowering sequences in Wisconsin. https://extension.soils.wisc.edu/wcmc/knowing-when-to-look-for-what-weed-emergence-and-flowering-sequences-in-wisconsin/
- Espinosa-García, F. J., R. Vázquez-Bravo, and M. Martínez-Ramos. 2003. Survival, germinability and fungal colonization of dimorphic achenes of the annual weed Galinsoga parviflora buried in the soil. Weed Research 43:269-275.
- Fracchia, S., A. Aranda, A. Gopar, V. Silvani, L. Fernandez, and A. Godeas. 2009. Mycorrhizal status of plant species in the Chaco Serrano woodland from central Argentina. Mycorrhiza 19:205-214.
- Garcia Freire, X. 2014. Biomass production and flowering of Galinsoga quadriradiata, and its competition with Lactuca sativa, in response to nitrogen and phosphorus. Honors Thesis, College of Agriculture and Life Sciences, Cornell University: Ithaca NY.
- Harley, J. L., and E. L. Harley. 1987. A check-list of mycorrhiza in the British flora. New Phytologist 105:1-102.
- Ivany, J.A., and R. D. Sweet. 1973. Germination, development, and growth of galinsoga. Weed Science 21:41-45.
- Jursík, M., J. Soukup, V. Venclová, and J. Holic. 2003. Seed dormancy and germination of shaggy soldier (Galinsoga ciliata Blake.) and common lambsquarters (Chenopodium album L.). Plant Soil Environment 49:511-518.
- Kumar, V., D. C. Brainard, and R. R. Bellinder. 2009. Effects of spring-sown cover crops on establishment and growth of hairy galinsoga (Galinsoga ciliata) and four vegetable crops. HortScience 44:730-736.
- Rai, J. P. N., and R. S. Tripathi. 1983. Population regulation of Galinsoga ciliata and G. parviflora. Weed Research 23:151-163.
- Rai, J. P. N., and R. S. Tripathi. 1984. Population dynamics of different seedling cohorts of two co-existing annual weeds, Galinsoga ciliata and Galinsoga parviflora, on two contrasting sites. Acta Oecologica 5:357-368.
- Rai, J. P. N., and R. S. Tripathi. 1986. Effects of density and soil nitrogen levels on growth of Galinsoga ciliata and G. parviflora in pure and mixed stands. Canadian Journal of Botany 64:2708-2715.
- Rai, J. P. N., and R. S. Tripathi. 1987. Germination and plant survival and growth of Galinsoga parviflora Cav. as related to food and energy content of its ray- and disc-achenes. Acta Oecologica 8:155-165.
- Shontz, N. N., and J. P. Shontz. 1972. Rapid evolution in populations of Galinsoga ciliata (Compositae) in western Massachusetts. American Midland Naturalist 88:183-199.
- Sweet, R. D. 1986. Life History Studies as Related to Weed Control in the Northeast 9. Galinsoga. Northeastern Regional Publication. Cornell University Agricultural Experiment Station: Ithaca, NY.
- USDA Plants. USDA, Natural Resources Conservation Service Plants Database. http://plants.usda.gov
- Warwick, S. I., and R. D. Sweet. 1983. The biology of Canadian weeds. 58. Galinsoga parviflora and G. quadriradiata (= G. ciliata). Canadian Journal of Plant Science 63:695-709