Riotous rudbeckias
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North America’s prairies are home to a wide range of
perennial daisies, including such well-known plants as the coneflower (Echinacea
purpurea) and the sunflower (Helianthus annuus), but among the most
striking, especially for late season colour are the rudbeckias.
Named after Olaus Rudbeck (1660–1740), a Swedish botanist,
there are around 15 species of Rudbeckia and, like Echinacea,
they are commonly known as coneflowers because their disc florets form a
prominent central cone.
While the less developed species, such as R. fulgida and
R. laciniata, may seem to produce an awful lot of foliage for the
quantity of flowers at their stem tips, Black-eyed Susan (R. hirta), its
cultivars and hybrids offer far more flower for your money.
Originally a rather rangy 1.5–2m tall plant with simple,
single, golden-yellow daisy heads, R. hirta has been extensively
hybridised, refined and developed so that it now occurs in single-,
semi-double- and double-flowered forms with blooms several times larger than
those of the wild species, on far more compact plants. What’s more, the flower
display lasts from late January until well into autumn.
Although Rudbeckia hirta is a biennial or short-lived
perennial, because it is so easily grown and inclined to become a little untidy
after the first season, it’s usually treated as an annual and raised afresh
from seed each spring. If you feel that you’d like to perpetuate some particularly
good forms, try leaving the clumps in the ground over winter and dividing them
in early spring or strike cuttings of the strong basal shoots.
For success rudbeckias require nothing more than
well-drained soil and sunshine. Afternoon sun will do, though all day is
better. Some forms grow too easily and may self-sow if given the chance.
Fortunately, they are easily controlled and not greatly inclined to
invasiveness.
Copyright Geoff Bryant
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