Zinnia elegans (youth-and-age, "Hyakunichiso")

Japanese name: ヒャクニチソウ （百日草）
Scientific name: Zinnia elegans

[Overview]
An annual 30–90 cm tall.
The stem is erect and stiff, with short hairs.
The leaves are simple and opposite, ovate to oblong, 4–10 cm long and 3–6 cm wide, with 3–5 conspicuous veins and stiff hairs.
The leaf margins are entire.
A single capitulum is borne at the end of each branch; in the wild species the ray florets around the edge of the inflorescence are reddish purple to pale purple, and the central tubular florets are yellow.
There are many cultivars, and their flower colors include almost every color except blue.

[History]
It arrived in Japan in the 2nd year of Bunkyu (1862), at the end of the Edo period.

[Cultivation]
Propagate from seed.
The ideal temperature for germination is 15–25°C, and for growth 10–30°C.
When planting in a flower bed, space plants about 30–40 cm apart, and it is good to make a somewhat raised ridge to improve drainage.
It prefers soil with good sunlight, ventilation, drainage, water retention and aeration.
In poor sun, flowering is poor or the flowers become small.
Splashing mud from rain or watering makes disease more likely, so for plants in the ground it is good to mulch around the base with bark compost or similar.
Water thoroughly when the soil surface dries, and it is good to water as close to the base as possible to prevent mud from splashing back.
In addition to base fertilizer, continue with chemical fertilizer once a month or liquid fertilizer about once every 10 days until the flowering period.
After flowering ends, cut back to a few nodes below the topmost bud; side shoots will then grow and you can enjoy a second flowering.
Pests and diseases include powdery mildew, aphids and spider mites.

[Notes]
The name comes from its long flowering period.

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