Spotted knapweed

2,7511,00

A reliable species for dry and sandy areas. The spotted knapweed is a medium-tall plant that lives two or many years. It is pollinated by a wide range of insects – flies, bees, bumblebees, butterflies.

Wild, non-cultivar seeds.

SKU: N089

About the species

Polish name:Rhenish knapweed

Latin name: Centaurea stoebe L. syn. C. rhenana Boreau p. Str.

Family: Asteraceae (composite Compositae), subfamily: Carduoidae

Status in Poland: native, common in many regions

Durability:
biennial
Flower color:
pink
Height:
about 75 cm
Flowering:
July-August

Morphology

The spotted knapweed is a tall or medium biennial plant, possibly short-lived.

It creates dense fields with the raspberry heads with a whitish center, often confused with “thistles” (actually: plume thistles), although without spikes on the leaves. It has a deeply penetrating taproot.

The shoots are upright, although in gardens they tend to lie down, strongly branched at the top, with the few, spiral arranged leaves.

It produces the pinnate leaves (with small, white-gray, shiny hairs), 50-150 mm long, with irregularly serrated blades. From June to August it creates inflorescences in the form of heads characteristic of knapweeds, made of a multitude of inconspicuous ray florets (sterile), and disc (bisexual, fertile) florets. In the case of the spotted knapweed, the heads reach 19.0-25.5 mm in diameter, are pale raspberry or light purple (sometimes white), they smell strongly and beautifully.

The fruit is a tiny achene, usually 3-5 mm long, with a short, multifunctional pappus. Depending on the conditions, this pappus either acts as a flying apparatus or as a velcro that clings to animal hair and human clothing.

Spotted knapweed is one of the few in the Polish flora of “steppe runners” (Greek: chamaechor, Ukrainian and Russian perekatypol, English tumbleweed), i.e. plants that detach from the ground completely after drying up and roll in the wind for thousands of kilometers in an openwork form structures made of the remains of shoots, leaves and whole infructescences, which facilitates the colonization of new areas.

Additional information

Sowing

It prefers sunny, dry and well-drained positions, sandy but quite fertile. It even tolerates barren soil.

Seeds It can be sown until the end of spring (late May). It can be sown by broadcast method on wastelands, or planted in prepare plots for it with parallel rows, separated by about 0.4 m. Cutting down the overblown heads will extend the blooming time considerably. Trimming individuals of this cornflower at a height of about 100 cm prevents lodging and at the same time stimulates tillering. It is sometimes attacked by aphids. After several years of growing this species in one place, there may be problems with subsequent crops in its former position.

 

Interesting facts

The spotted knapweed is an extremely competitive plant. This is mainly due to its allelopathic effect on other species, i.e. the secretion of secondary metabolites into the soil, which are more harmful to other plants than to this one. Therefore, the presence C. stoebe causes erosion of top soil layers. Most herbivores are reluctant to eat it.

The spotted knapweed has become an invasive species dangerous for agriculture and native wild flora in Canada and the USA, mainly in the west. It was probably found there as an alfalfa weed at the end of the 19th century. It immediately mastered not only arable fields, fallow lands, pastures with too many cattle and horses, places around canals and oil pipelines, post-industrial areas and roadsides, but also sandy river banks, semi-deserts and prairies, especially in naturally disturbed places, e.g. by buffalo feeding grounds or colonies prairie dogs. Many American and Canadian scientists have been studying various aspects of the invasion of this cornflower for decades. There are still debates about the exact mechanism of soil sterilization and removal of other plant species. In order to get rid of the spotted knapweed, a number of insect species were imported from America, methods of forcing sheep to eat cornflower were also developed, and various other agrotechnical treatments (herbicides + mowing with burning hay and reclamation of topsoil layers) are still being perfected. On the other hand, there are voices among American beekeepers to stop fighting C. stoebe, and even deliberately sow it as an excellent honey plant.

Use Value

The spotted knapweed has long been highly valued by beekeepers. Depending on the conditions, it gives 500-600 kg of nectar and as much as 260 kg of pollen per hectare of field margin / apiary. Liked for its rapid pace of development from seed to flowering specimen (several months), low soil requirements, pleasant smell, and excellent quality of nectar for bees and honey for humans. Beekeepers usually broadcast it on wastelands, while on plots with a spacing of 20 x 40 cm. In addition to the honey bee, it is also visited by the bumblebees and the solitaries (the leafcutting bees, the pantaloon bees, the small carpenter bees, the sweat bees, the miner bees, and the anthophora bees).

Featured products