Few-petalled Daisies
What are they?
The compound heads of small yellow florets and outer ring of white petals show these plants to be members of the daisy and dandelion family - the Asteraceae. However, these plants have a greatly reduced number of petals than is typical of daisies and often have just five petals, or at least less than ten. These are small, 'weedy' annuals, typically less than 50cm tall.
Where are they found?
These plants are all introductions and are likely to be found on tilled ground in gardens, allotments and other disturbed places or where self-seeding from original plantings.
Identification
The identification of these species is fairly straight forward, although confirmation of the Galinsoga species is best done by studying the tiny, scale-like bracts that are found in the flowerhead, in the spaces between the tiny, yellow florets. If the flowers already have seeds present, the feathery scales at the top of the seed - called the pappus - can be also be used for identification.
Gallant Soldier Galinsoga parviflora
Introduced from South America. Scattered here and there on disturbed ground, especially in urban habitats and on sandier soils; also frequent in some areas as an arable weed. Flowers May to October. Leaves and stems with only a scattering of short hairs. Tiny scales in the flowerhead are three-pointed towards their tips. Pappus scales on the seed tops have fringing hairs and blunt tips.
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Shaggy Soldier Galinsoga quadriradiata
Introduced from South America. Scattered here and there on disturbed ground, especially in urban habitats and on sandier soils. Generally less common than Gallant Soldier. Flowers May to October. Leaves and stems usually with an obvious coat of whitish hairs. Tiny scales in the flowerhead taper to a single point at their tips. Pappus scales on the seed tops have slender, long-pointed tips.
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Black-jack Bidens pilosa
Originally from South America but now widely introduced in warmer parts of the world. Formerly occurred as a rare introduction from bird seed or wool waste but there have been no recent records. Flowers June to September. Flowerheads to 2cm in diameter, typically with five to eight, white petals. Leaves very variable, often three-parted but may also be simple or up to seven-parted.
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Mexican Cosmos Cosmos bipinnatus
Introduced from Central America as a garden ornamental and occasionally found as a survivor from previous plantings or occasionally when self-seeded. This plant has become an invasive problem in some parts of the world but our winters are currently too cold for it. Flowers July to September. May grow to over a metre in height with flowers either white or various shades of pink and 4.5-9cm in diameter, typically with eight petals. Leaves very deeply cut into narrow, linear strands.
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Garden Dahlia Dahlia x hortensis
Originally introduced from Central America, where already long-cultivated by the time of the Spanish Conquest. Continuing artifical breeding has produced a wide variety of plants with flowers in many colours and forms. Flowers July to October. Plants from 50-200cm in height with leafy stems arising from potato-like tubers. Leaves variously three- to seven-lobed with coarsely toothed margins. Flowers highly variable, from Cosmos-like 'daisy' flowers with eight petals, to highly modified and selected forms with twisted, rolled or otherwise ornamental petals.
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Pinnate Dahlia Dahlia pinnata
Originally introduced from Central America and widely cultivated to produce a range of cultivars and hybrids. Flowers July to October. Plants from 50-215cm in height with leafy stems arising from potato-like tubers. Leaves variously three- to seven-lobed with coarsely toothed margins. The true Dahlia pinnata is probably not in cultivation and there is no clear distinction between cultivars of it and hybrids between D. pinnata and D. coccinea, with hybrids typically referred to as one or other of the parents in the past. Currently, there is a range of small, bedding dahlias referable to Pinnate Dahlia, that are widely planted in amenity areas and may occur as throw-outs on rough ground. These are illustrated here.
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