Sunflower, Coneflowers & Allies
What are they?
Marigolds and related plants form a group of often showy, yellow- or orange-flowered members of the daisy and dandelion family - the Asteraceae. Their flowers differ from those of the dandelions in having strap-like petals or 'rays' around the outside of the compound flowerhead only, with the small florets in the centre being petalless and forming a button-like middle. These plants are annuals or herbaceous perennials and are often grown in gardens for their showy flowers, whichcan be produced throughout the summer. The plants tend to be multistemmed, while the flowerheads are mostly carried singly on long stems.
Where are they found?
Most are plants that are grown ornamentally and are most likely to be found as garden escapes or throw-outs on roadsides, waste ground or other grassy places. Corn Marigold is a weed of arable margins.
Identification
The flowers of this group can seem all rather similar at first, so it pays to make a note of leaf detail and to take a close look at the phyllaries (the green bracts around the base of the flowerhead), which should make identification relatively straight forward.
Annual Sunflower Helianthus annuus
Introduced from North America and well-known both as a garden ornamental and as the source of sunflower seed. Occasionally found as a self-sown stray from agricultural plantings or from spilt bird food. Flowers July to October. Cultivated forms are easily identified by virtue of their height (sometimes to 5m or more!) and their massive flowerheads up to 30cm across. Self-sown plants tend to more closely resemble the true species, being much shorter (to 100cm) and having smaller flowers that appear on side branches, rather than a single, large flower at the top of the main stem. In the photos below, the first row shows the larger-flowered form, while the lower row shows smaller, self-sown plants.
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Perennial Sunflower Helianthus x laetiflorus
Occurs as a natural hybrid in North America but plants in the UK originated in cultivation. Grown as a garden ornamental and occasionally recorded as a garden escape or throw-out on rough ground. Flowers September to October. A tall perennial plant, to two metres in height. Very similar to Jerusalem Artichoke but grown as a an ornamental for its flowers and differing mostly in its phyllaries, which are 5-12mm in length and mostly pressed against the flowerhead.
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Jerusalem Artichoke Helianthus tuberosus
Introduced from North America as a root vegetable and occasionally found as a relic of cultivation. Flowers July to October. Spreads readily from a creeping rootstock, so often found forming loose colonies of many stems. Stems have rough, bristly hairs on them. Very similar to Jerusalem Artichoke and differing mostly in its phyllaries, which are 11-18mm in length and spread more openly.
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Black-eyed Susan Rudbeckia hirta
Introduced from North America as a garden ornamental and occasionally found as a relic of cultivation. Flowers July to October. An annual or short-lived perennial that doesn't persist for long. The whole plant is covered in rough hairs, the stem hairs having swollen, reddish bases. Flowers are usually yellow with a dark centre, but some cultivated varieties may have orange or red tones.
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Cut-leaved Coneflower Rudbeckia laciniata
Introduced from North America as a garden ornamental and occasionally found as a relic of cultivation where it may persist for a number of years. Flowers July to October. A perennial species that may grow to two metres in height. Stems more or less hairless. Leaves very variable, from simple and deeply toothed/lobed to pinnate.
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False Sunflower Heliopsis helianthoides
Introduced from North America as a garden ornamental and once recorded as a garden throw-out in Cambridge. Flowers August to October. A perennial species that may grow to 1.5 metres in height. Stems more or less hairless. Leaves opposite. Can readily be told from the true sunflowers (Helianthus spp.) by the jointed appearance of the stems at the leaf nodes.
There are two forms of this species, one with smooth leaves and stems (var. helianthoides) and one with rough leaves and stems (var. scabra). The former is often known as Rough Oxeye and the latter as Smooth Oxeye. Since this is confusing when it is not clear which variety is present, I have used the more widely used, North American name.
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Large Blanket-flower Gaillardia x grandiflora
A garden hybrid, it's parents originating from North America. Commonly cultivated and occasionally found where garden waste has been dumped on roadsides or rough ground. Flowers July to September. Flowers reddish with a yellow border of variable width. Phyllaries and leaves rather variable, reflecting a spectrum of intermediates between the parents. Leaves may be simple, toothed or lightly lobed.
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Golden Tickseed Coreopsis tinctoria
Introduced from North America as a garden ornamental and occasionally found as where included in so-called 'wildflower mixes'. Flowers July to October. A small plant, to around 50cm in height. Each leaf is deeply cut into a complex bunch of narrow segments.
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