What are the origins of the Alpine blue thistle?
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Latin name:
Eryngium alpinum.
Botanical family:
Apiaceae (formerly Umbellifera) such as carrot, fennel and celery.
Main types:
Several species of the genus
Eryngium
grow naturally in France.
This is the case of
E. giganteum,
a biennial reaching up to 1.5 m in height or
Eryngium maritimum
, smaller (50 cm) recognizable by its more thorny glaucous green leaves.
Origin:
Western Alps.
But beware: the Alpine blue thistle is a rare and protected species whose collection and transplantation are prohibited by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites).
It can be found commercially, but the seller must provide a certificate that the plant was not collected from the wild.
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What are the uses of Alpine blue thistle?
In massive or rockery.
The inflorescences, once dried, allow you to make pretty bouquets.
How to recognize the Alpine thistle?
Also called Alpine panicaut,
Eryngium alpinum
is a large, deciduous, bushy perennial plant that can reach 90 cm high and 50 cm wide.
Its tiny flowers, blue or white, are very popular with pollinating insects.
They form very graphic cylindrical umbels of a beautiful steel blue supported by superb flexible spiny bracts.
Flowering period:
From the end of June to the end of August.
Hardiness:
Non-frost plant provided the soil is sufficiently draining.
Fears scorching temperatures in summer.
How to cultivate it?
Difficulty level:
Easy.
Soil:
Well draining but cool with a neutral to slightly basic pH.
Read also: The right pH, a guarantee of future good harvests
Exposure:
The panicaut des Alpes needs maximum light.
It will therefore be displayed in full sun in mountain gardens.
In the plains, the south-eastern exposure will protect it from heat stroke in July-August.
Sowing / planting:
Sowing can be done in place from May or in the fall under a cold frame.
It is also possible to make root cuttings in winter in sand, always under a cold frame.
Cultivation management:
This plant sensitive to heat and drought can only be grown in the ground because its taproot requires a good depth of soil.
Cool temperatures result in darker flowers.
Watering is not necessary if the soil is naturally cool.
After flowering, cut the foliage and cover the stump.
Do not let the soil soak up water in winter to avoid root rot, especially in clayey conditions.
Common diseases and pests:
Protect young plants from slugs and snails and watch for blight attacks if the humidity is too high.
Sheet written by Philippe Lemettais,
SNHF,
Orchids section.