Perennial plant - perennial

Japanese: 多年草 - たねんそう（英語表記）perennial

Herbaceous plants that live for more than two years and are evergreen or have parts above ground that die during winter, but the stems, leaves and roots near the ground survive and sprout again the following spring, grow and bloom, are called perennials. Originally, perennials were also called perennial plants and are treated the same. In floriculture, perennials (perennial plants) broadly include bulbs and other plants based on their continuous growth period, but are differentiated in terms of cultivation. They also do not include biennial plants, whose seeds are sown from summer to autumn and which bloom from winter to spring.

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Cultivation considerations

When cultivating perennial plants, it is important to know their place of origin and manage them so that they adapt to the climatic and soil conditions.

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Climate conditions

Even in Japan, there are differences between areas with snowfall in winter and areas without snowfall. In particular, in areas with low temperatures and dryness in winter, such as the Pacific coast, plants with poor root development are likely to be lifted up by frost. Some plants are also prone to growth inhibition due to excessive humidity during the rainy season and the subsequent abnormal rise in soil temperature, which causes them to dry out.

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Soil conditions

Most perennial plants prefer soil that is well-drained and has good water retention, but depending on their place of origin, some prefer humus, and some grow better with limestone.

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Repotting

Some plants only need to be planted once, but some species have a strong aversion to certain soils, and some will not grow well in pots unless they are constantly repotted in new soil. On the other hand, some plants grow too large and slow down or are prone to root rot, so they need to be repotted according to their characteristics.

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Breeding

Although they can be propagated by seeds, they can also be propagated by division, cuttings, grafting, etc. (1) Division They are divided based on the number of 3-5 rows (buds), and for those that mainly flower in the spring, autumn is the best time to plant them, while for those that flower from summer to autumn, spring is the best time to plant them. There are also some species such as Japanese iris that do best in the summer after flowering. (2) Propagation (cuttings, leaf cuttings, root cuttings) For perennials whose stems are not woody, this is often called cuttings. For those with strong rooting abilities, they can be propagated simply by cutting off leaves or roots and inserting them. (3) Grafting This method is used when it is difficult to propagate plants by division or cuttings. There are also special cases where Clematis is grafted onto a rootstock such as a C. quinquefoil.

[Yasuo Hori]

Main perennial plants
©Shogakukan ">

Main perennial plants

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

草本植物で2年以上生存し、常緑または越冬の際地上部の一部は枯死するが、地際に近い茎葉と根部は生き残り、翌春ふたたび萌芽(ほうが)して成長開花するものを多年草とよぶ。本来、多年草は宿根草ともいい同じ扱いをしている。花卉(かき)園芸面では、その生育永続期間よりみて、多年草（宿根草）とは、広義には球根類なども含むが、栽培上は区別している。また夏から秋にかけ種子を播(ま)き、冬から春にかけて開花する二年草は含まない。

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栽培上の留意点

多年草（宿根草）の栽培にあたっては、原産地を知ったうえで気候条件、土壌条件になじむように管理することがたいせつである。

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気候条件

日本でも冬季積雪地域と無積雪地域とでは差がある。とくに太平洋側のように冬季の低温乾燥地域では根張りの悪いものは霜で浮き上がりやすい。また梅雨期の過湿やその後の地温の異常な上昇で乾燥し、生育が阻害されやすいものもある。

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土壌条件

多年草のほとんどのものは排水もよく保水性もある土質を好むが、原産地によっては腐植質を好むものや、石灰質があったほうがよく生育するものなどがある。

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植え替え

一度植え付けるだけでよいものもあるが、種類によっては忌地(いやち)性の強いものがあり、鉢物ではつねに新しい用土で植え替えてやらないと育ちの悪いものもある。一方、株が殖えて大株になりすぎて生育が衰えたり、根腐れをおこしやすいものもあるので、特性にあった植え替え管理が必要である。

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繁殖

種子繁殖もできるが、株分け、挿芽、接木(つぎき)などの方法で殖やすことができる。（1）株分け　3～5条（芽）を基準に分けるが、主として春に開花するものは秋、夏から秋に咲くものは春がよい。またハナショウブのように開花後の夏季がよいものもある。（2）挿木（挿芽、葉挿、根挿）　茎が木化していない多年草類では、挿芽とよぶことが多い。発根性の強いものでは、葉や根を切断したものを挿すだけでも殖やすことができる。（3）接木　株分けや挿芽が困難なものを殖やす場合に行う方法である。クレマチスではセンニンソウを台木として接木するような特殊な例もある。

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おもな多年草

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