Pineappleweed An introduced annual weed of wasteland and bare places by paths. Pineappleweed was introduced into the UK just prior to 1900 and within 25 years it had spread along roadsides Pineapple Weed Seeds Pineapple Weed Matricaria discoidea Aster family (Asteraceae) Description: This annual plant is about 3-12″ tall, branching frequently and having the appearance Pineapple Weed This is an annual weed, reproducing by seeds. The stems are erect, up to 40 cm tall, branched, hairless, and smooth. The leaves are alternate, hairless, very finely divided, and
An introduced annual weed of wasteland and bare places by paths. Pineappleweed was introduced into the UK just prior to 1900 and within 25 years it had spread along roadsides throughout most of England. Pineappleweed is now common throughout the UK, and is still increasing, especially on tracks and paths and on cultivated land. It prefers an open loamy or sandy loam soil.
Pineappleweed occurs in cereals and broad-leaved arable crops and has become a frequent weed of intensive vegetable crops. It is also a common garden weed.
Pineapleweed is used medicinally, including as an effective worming treatment. The flowers smell of pineapple when crushed.
Pineappleweed flowers from June to September, sometimes into November. Insects seldom visit the flowers. Seed is set from July onwards within 40-50 days of flowering. The average seed number per plant ranges from 850 to 7,000. The 1,000 seed weight is 0.13 g.
Seed germination is promoted by light, just a short flash is sufficient. In the laboratory, germination is increased by a period of dry-storage. Seed sown in field soil and cultivated periodically emerged from February to November with peaks from March to May and August to October.
Plants emerging from January to April remain vegetative for longer before flowering than plants emerging from mid-May to mid-July that take just 40-50 days to flower. All set seed and die before winter. Plants that emerge after August are likely to overwinter as vegetative rosettes that do not flower until the following spring. Daylength is the controlling factor and flowering is delayed at a shorter daylength.
In sandy loam soil, seedlings emerge from the top 0-10 mm of soil with the majority emerging from the surface 5 mm.
Based on seed characters, pineappleweed seed should persist for longer than 5 years in soil. Seed mixed with soil and left undisturbed declined by 83% after 6 years but in cultivated soil the decline was 91%. Seed buried in sub-arctic conditions had 20% viability after 6.7 years.
Seeds are dispersed in mud and by rain splash. Mud on the tyres of cars was responsible for much of the early spread. The seeds are light enough to be blown by the wind and by passing traffic. Viable seeds have been found in horse droppings.
Seedlings and larger plants should be controlled by cultivation and hand weeding to prevent seeding. Pineappleweed seedlings are more numerous on tine-cultivated or no-till land than ploughed land.
In grassland, pineappleweed is able to colonise areas around gateways and troughs where livestock have trampled and caused poaching.
Pineapple Weed Seeds
Aster family (Asteraceae)
Description: This annual plant is about 3-12″ tall, branching frequently and having the appearance of a miniature bush. Fern-like leaves up to 2″ long and �” across alternate along the hairless stems. These simple, double, or triple compound leaves are pinnately divided into linear lobes. From the axils of the upper leaves, there develops flowerheads on stalks about �–1�” long. The flowerhead of each stalk is about 1/3″ across, and consists of numerous greenish yellow disk florets and no ray florets. Each disk floret has 4 tiny lobes at its apex. The base of the flowerhead has several overlapping green bracts that are lanceolate or ovate with papery upper margins. The top of the flowerhead is shaped like a dome or blunt cone. Both the foliage and flowerheads have a pineapple-like odor when they are bruised or crushed. The blooming period occurs during the summer and lasts about 1-2 months. Each disk floret is replaced by an oblong achene that is broader at the top than the bottom. The achenes are without awns or tufts of hairs. The root system consists of a branching taproot. This plant spreads by reseeding itself.
Cultivation: The preference is full sun, mesic conditions, and gravelly or compacted soil. Competition from taller plants is not tolerated for very long.
Range & Habitat: Pineapple Weed is a common plant in central and northern Illinois, but it is somewhat less common in the southern areas of the state (see Distribution Map). This plant is adventive from the Pacific Northwest. In addition to eastern North America, Pineapple Weed has since spread to northern and western Europe, where it is not native. Habitats include stony slopes of pastures, barnyards, edges of driveways and sidewalks, gravelly areas along railroads and roads, and sunny waste areas that are rocky or gravelly. Disturbed areas are strongly preferred.
Faunal Associations: The flowerheads attract flower flies (Syrphidae) and are probably pollinated by them. Little is known about this plant’s relationship to birds and herbivorous mammals in the NE or Midwest. Cattle reportedly make little use of it as a food source. It is possible that the seeds or flowerheads stick to the tires of motor vehicles and for this reason Pineapple Weed often occurs along roadsides and driveways.
Photographic Location: Along a gravelly slope near a driveway in Urbana, Illinois.
Comments: This odd-looking little plant is closely related to the mayweeds, chamomiles, and other weedy daisies that have been introduced into North America from abroad. They share the same kind of highly dissected foliage. However, Pineapple Weed lacks white ray florets in its flowerheads, unlike the others, and it is less showy in appearance as a result. Another scientific name for this species is Matricaria matricarioides. The common name refers to the scent of the foliage and flowerheads, and possibly the appearance of the latter.
This is an annual weed, reproducing by seeds. The stems are erect, up to 40 cm tall, branched, hairless, and smooth. The leaves are alternate, hairless, very finely divided, and pineapple scented when crushed. The flowers are very small, grouped into head, and yellowish-green in colour. Flower heads are dome-shaped and resemble miniature pineapples. The tubular florets are surrounded by a series of involucral bracts which have broad whitish translucent edges. The seeds are olive or brown in colour, 1.0 x 0.3 mm in size, and one per flower.
Take a minimum of 20 weed counts across the field. Check roadsides, waste areas, yards, and disturbed ground for patches of this weed. May occur in high traffic areas such as walking paths.