Solidago altissima ("Seitakaawadachiso")

Japanese name: セイタカアワダチソウ （背高泡立草）
Scientific name: Solidago altissima

[Overview]
A perennial 1–2 m tall that forms large colonies on sunny banks and vacant lots.
It spreads well by extending underground stems.
The stem and leaves have short hairs and are rough to the touch.
The leaves are simple and alternate, lanceolate, 6–13 cm long and 1–2 cm wide, with three conspicuous veins.
The leaf margins are entire or have low teeth.
There is a short petiole.
On the upper side of the branches, yellow flower heads about 5 mm across are densely arranged, forming a large conical inflorescence as a whole.
Both the ray flowers and the tubular flowers are yellow.
There are 10–18 ray flowers per flower head.
The fruit is an achene with pappus.

[History]
It was introduced around 1900 as an ornamental and a nectar source plant, and became widely naturalized after the war.
It releases allelopathic substances from its roots and underground stems, suppressing surrounding plants and forming colonies.

[Cultivation]
Propagate by division.
It prefers sunny, well-drained soil.
It is cold-hardy and heat-tolerant, and is robust and easy to grow.
For potted plants, water thoroughly when the soil surface dries; for plants in the ground, rainfall is sufficient unless summer brings a long spell of sunny weather and the soil becomes severely dry.
If basal fertilizer is applied, no further fertilizer is particularly needed, and too much may cause the plant to become leggy and fall over.
When the plant grows tall, it is good to put up stakes so that it does not fall over.
Pests and diseases include powdery mildew, rust, leaf miners, lace bugs, spider mites and aphids.

[Notes]
It is designated as an invasive alien species requiring caution under the Invasive Alien Species Act.

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