COMMON RAGWEED Science Page DID YOU KNOW? Pollen from common THE COMMON RAGWEED PLANT .usbg.gov w male flower ragweed and giant ragweed Common ragweed is an annual, meaning is the main cause of hay ww pollen it lives only one season. It is one of the fever in North America. first plants that grows where the soil Each ragweed plant can has been disturbed -- in fields, gardens, produce up to a billion roadsides, and waste places. pollen grains. Wind can The plant There are separate female and single pollen carry the light pollen up to grows up male flowers on each plant. grain 640 km (400 miles). It is to 150 cm (magnified) (5 feet) The female flowers axil easy for people to inhale tall. are in the axils of the tiny pollen grains. the upper leaves. UNITEDSTATES BOTANIC GARDEN The male flowers female flower ORIGINS are tiny yellow- Most of the 30 or so green bells on spikes ragweed species are near the tops of the plants. Pollen release native to North and begins in the middle South America. Common of the growing season, peaks by late ragweed is the most Common summer, and ends widespread of all the male flower ragweed was with a ragweeds. It was killing frost. named for the accidentally imported raggedy shape to Europe in the 1940s, of its leaves. and has spread widely throughout many parts The seed pods are small prickly burrs that stick Common ragweed often grows on to the fur and feathers of animals passing by. seed of Europe since then. abandoned farms in Eastern Europe. Each burr contains a single seed. pod CLASSIFYING COMMON RAGWEED FAMILY sunflower GENUS SPECIES Asteraceae (sunflower family) Ambrosia artemisiifolia Asteraceae is the Ragweeds were named after the delicious This Greek name refers to the largest family of dandelion food eaten by the Greek gods to make fact that common ragweed flowering plants, and them live forever. It is not known why this leaves look like those of includes about 1,100 name was given to ragweed. Perhaps it plants in the genus Artemesia. was because horses liked to eat ragweed. genera and 20,000 leaf of species. All the common ragweed Giant plants in this family Common ragweed (A. artemisiifolia) have tiny flowers ragweed (A. (A. artemisiifolia) trifida) grows up to 1.5 m packed together. Look closely next grows up to (5 ft). time you see a daisy 4 m (13 ft). or a dandelion. What looks like one flower is actually many little chicory flowers. leaf of wormwood common (Artemesia absinthium) ragweed FRIEND... ...OR FOE? Many people UNITED STATES BOTANIC GARDEN BOTANIC STATES UNITED suffer from Ahh... hay fever and ..choo!! asthma caused by ragweed pollen. Common ragweed and Common ragweed giant ragweed provides food and cause more ww hay fever than w shelter for animals. .usbg.gov Rabbits and grasshoppers eat the all other plants leaves. Voles and many different put together. species of birds eat the seeds. SPOTLIGHT .usbg.gov PUZZLE ON RESEARCH w Word Scramble Roadside Ragweed ww Pollen from Common and Giant (1) AWREGED Dr. DiTommaso, a weed scientist at Cornell causes more hay fever than all other plants put University, noticed that common ragweed forms together. Ragweed belongs to the (2) dense stands along roadsides where large SACERAETEA family, and the genus (3) amounts of salt are applied to help remove snow SOMARAIB. (4) MOCOMN ragweed is the most and ice in winter. Dr. DiTommaso hypothesized widespread of all the ragweeds. The scientific that this is because ragweed can easily adapt name of common ragweed is Ambrosia (5) to salty soils. That is, ragweed can develop the MEISFIAROTAILI. It is an (6) LUNANA, meaning ability to sprout and grow in salty soils. Other UNITEDSTATES BOTANIC GARDEN it lives only one season. (7) LEAM ragweed plants cannot adapt to salty soils as well. flowers are on spikes near the tops of plants. To test his hypothesis, Dr. DiTommaso designed and carried out an experiment to see how well ragweed seeds can germinate TRY THIS in salt water. He compared seeds taken from Find a plant more salt-tolerant than salty roadsides with seeds taken from fields. According to his hypothesis, the ragweed seeds common ragweed What you need taken from roadsides should germinate better in * salt solution: 15 ml (1 tablespoon) of salt in salty water than the seeds taken from fields. 1 liter (a quart) of water He collected ragweed seeds from along * water * paper towels * waterproof roadsides and from different fields. He placed * seeds to test * clear plastic cups marker seeds from each location on filter paper in sealed dishes, and moistened the filter paper What to do in each dish with distilled water (the control) 1. Go to a roadside that is heavily salted in or with one of four different salt solutions, winter. Collect some ragweed seeds from from slightly salty to very salty. All the dishes plants that have over-wintered. CAUTION: were kept in controlled temperature and light DO THIS ONLY UNDER ADULT SUPERVISION, conditions (similar to spring time conditions). AND WATCH FOR TRAFFIC! You will also Then he counted the number of seeds that need to get seeds of salt-tolerant cover germinated in each dish for 21 days. crops, such as trefoil or alfalfa, from a In the saltiest water, 31% of the ragweed gardening supply store. seeds from roadsides germinated, and only 2. You will need six cups for each kind of seed 3% of the seeds from fields germinated. These you test––three will be moistened with salt results very strongly support the hypothesis: water and three with fresh water (the ragweed can easily adapt to salty soils. control). For the ragweed seeds, write This study may explain why attempts to grow “ragweed” on the sides of six cups. Write groundcovers along salty roadsides have “salt water” on the sides of three of the failed -- ragweed quickly crowds them out. cups and “fresh water” on the other three. Plant scientists now need to test different For each of the other kinds of seeds you groundcovers to find out which ones can test, label six cups in a similar way. Line compete with ragweed in salty soils. the inside of all the cups with a paper towel Source: DiTommaso, A. (2004). Germination behavior of common and stuff paper towels into the center of the ragweed (Ambrosia artemisiifolia) populations across a range of cups. salinities. Weed Science 52:1002-1009. 3. Place seeds between the towels inside of the cups. Put 10 seeds evenly spaced in each “...” cup, about 2-3 cm (1 in) from the bottom QUOTE of the cup. Label what kind of seeds are in “A square-mile field of ragweed plants can each cup. yield sixteen tons of pollen in a year, yet only ww 4. Moisten the towels in each cup with either a millionth of a gram can start an allergic w salt water or fresh water. The seeds should MOSAICS GARDEN response of the kind that can send many of us .gardenmosaics.org be moist, but not under water. into fits of sneezing, scratching, coughing and 5. Keep the cups in a warm place, not in direct wheezing.” sunlight. Add either fresh or salt water as Source: Nesse, R.M. and Williams, G. (1994, Nov/Dec) Nothing to needed. Sneeze At. The Sciences, pgs. 34-38. 6. Count the number of seeds that germinate in each cup over a couple of weeks. Make a graph to record your results. .