Index
Practical ecological knowledge for the temperate reader.

Centaurea Sp. - Knapweed

Family: Asteraceae (Aster) [E-flora]

"Annual to perennial herb. Stem: prostrate to erect, generally ± branched, generally ribbed, occasionally winged. Leaf: basal and cauline, alternate; proximal generally 1–2-pinnately lobed; distal generally ± reduced. Inflorescence: heads disciform or radiant (discoid); involucre cylindric to hemispheric; phyllaries graduated in 6–many series, generally ± ovate, scarious-margined, tip appendages fringed to spiny; receptacle flat, epaleate, long-bristly. Flower: corolla white to pink, purple, or yellow, tube long, distally bent; outer flowers generally sterile, corolla 3–10-lobed, ± bilateral, reduced, inconspicuous or expanded and spreading, ± ray-like; inner flowers bisexual, corolla ± radial; anther base tailed, tip oblong; style tip cylindric, minutely hairy distal to hairy ring, branches very short. Fruit: ± barrel-shaped, ± compressed, attached ± at side; pappus 0 or generally of stiff, unequal bristles or narrow scales.
± 500 species: especially Eurasia, northern Africa; some cultivated. (Greek: plant name associated with Chiron, a centaur) [Keil & Ochsmann 2006 FNANM 19:181–194] Many noxious or invasive weeds." [Jepson]

Local Species;

  1. Centaurea cyanus - cornflower [E-flora]
  2. Centaurea diffusa - diffuse knapweed [E-flora]
  3. Centaurea melitensis - Maltese star-thistle [E-flora]
  4. Centaurea montana - mountain bluet [E-flora]
  5. Centaurea nigra - black knapweed [E-flora]
  6. Centaurea nigrescens - short-fringed knapweed [E-flora]
  7. Centaurea stoebe - spotted knapweed [E-flora]
  8. Centaurea x moncktonii - meadow knapweed [E-flora]

References


Uses of Related Sp.


Centaurea cyanus - cornflower

"Centaurea cyanus is a ANNUAL growing to 1 m (3ft 3in) by 0.3 m (1ft) at a fast rate. It is not frost tender. It is in flower from June to August, and the seeds ripen from August to October.
The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, flies, Lepidoptera (Moths & Butterflies). The plant is self-fertile. It is noted for attracting wildlife. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: acid, neutral and basic (alkaline) soils and can grow in very alkaline soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought." [PFAF]

"General: Annual herb from a taproot; stems erect, branched, loosely hairy, 0.2-1.2 m tall." [IFBC-E-flora]

"Leaves: Basal leaves linear to lanceolate, entire or with a few teeth and narrow lobes towards the base, white-woolly below, up to 13 cm long and 1 cm wide, soon deciduous; stem leaves similar, reduced and narrower upwards." [IFBC-E-flora]

Habitat/Range: "Dry roadsides in the lowland and montane zones; infrequent in S BC; introduced from the Mediterranean region." [IFBC-E-flora]

Status: Exotic [E-flora]

Food Use

Other Use

Medicinal Use

"Cornflower has a long history of herbal use, though it is seldom employed nowadays. In France it is still used as a remedy for tired eyes, but opinions differ as to its efficacy[254, 268]." [PFAF]

Cultivation & Propagation

"Succeeds in ordinary garden soil[1, 200]. Prefers a well-drained fertile soil and a sunny position[200]. Tolerates dry, low fertility and alkaline soils[200]. Established plants are drought tolerant[201]. A very ornamental plant[1], there are many named varieties[188]. The flowers are often used in dried-flower arrangements because they retain their colour well[7]. A good plant for bees, butterflies and moths[20, 30, 108]. The cornflower is considered to be a good companion, in small quantities, for cereal crops[18, 20], though another report says that its greedy roots deprive the cultivated plants of nutrients and its tough stem dulls the reaper's sickle[4]. Members of this genus are rarely if ever troubled by browsing deer[233]." [PFAF]

"Seed - sow March in the greenhouse. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in May. The seed can also be sown in situ during April, whilst in areas where the winters are not too cold a sowing in situ during September will produce larger and earlier-flowering plants" [PFAF]

Synonyms

References


Centaurea diffusa - diffuse knapweed

"General: Annual, biennial or short-lived perennial herb from a taproot; stems erect, branched, sparsely hairy, 10-60 cm tall." [IFBC-E-flora]

"Leaves: Basal leaves pinnately divided into linear segments, broadly lanceolate in outline, 3.5-20 cm long, 0.5-3.5 cm wide, grey-green, lightly dense-hairy, soon deciduous; stem leaves similar, reduced upwards." [IFBC-E-flora]

"Habitat / Range Dry roadsides, disturbed areas, overgrazed grasslands and shrublands in the steppe and lower montane zones; common in S BC east of the Coast-Cascade Mountains; introduced from the E Mediterranean region." [IFBC-E-flora]

Status: Exotic [E-flora]

Synonyms

References


Centaurea melitensis - Maltese star-thistle

"Centaurea melitensis is a ANNUAL growing to 0.5 m (1ft 8in). It is hardy to zone (UK) 7. It is in flower from July to September, and the seeds ripen from September to October.
The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, flies, Lepidoptera (Moths & Butterflies). The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought." [PFAF]

"General: Annual herb from a taproot; stems erect, winged, ridged, branched, 15-70 cm tall." [IFBC-E-flora]

"Leaves: Basal leaves oblanceolate, toothed to lobed, hairy; stem leaves becoming lanceolate to linear-oblong, entire and reduced." [IFBC-E-flora]

"Habitat / Range Mesic disturbed areas in the lowland zone; rare in SW BC, known recently only from Samuel and Georgeson Islands in the Gulf Islands; introduced from the Mediterranean region." [IFBC-E-flora]

Status: Exotic [E-flora]

Medicinal Uses

Cultivation & Propagation

"We do not have information on this species, but the following notes are based on the closely related C. solstitialis. Succeeds in ordinary garden soil[1, 200]. Prefers a well-drained fertile soil and a sunny position[200]. Tolerates dry, low fertility and alkaline soils[200]. A good bee and butterfly plant the flowers are rich in nectar[171]. Members of this genus are rarely if ever troubled by browsing deer[233]." [PFAF]

"Seed - sow April in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and plant them out into their permanent positions in the summer. If you have sufficient seed it can be sown in situ in the spring, and an autumn swing in situ might also be worth trying." [PFAF]

References


Centaurea nigra - black knapweed

"Centaurea nigra is a PERENNIAL growing to 0.6 m (2ft). It is hardy to zone (UK) 5 and is not frost tender. It is in flower from June to September, and the seeds ripen from August to October.
The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, flies, Lepidoptera (Moths & Butterflies). The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: acid, neutral and basic (alkaline) soils and can grow in very alkaline soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought." [PFAF]

"General: Perennial herb from a taproot; stems erect, branched, rough-hairy, 10-80 cm tall." [IFBC-E-flora]

"Leaves: Basal leaves oblanceolate, long-stalked, toothed or shallowly lobed to entire, long-hairy above and below, the blade up to 15 cm long and 3 cm wide; stem leaves reduced and becoming unstalked upward." [IFBC-E-flora]

"Habitat / Range Mesic to dry roadsides and fields in the lowland and montane zones; rare in S BC south of 51degreeN; introduced from Europe." [IFBC-E-flora]

Status: Exotic [E-flora]

Food Use

"Flower petals - raw. Added to salads[183]." [PFAF]

Medicinal Use

"The roots and seeds are diaphoretic, diuretic, tonic and vulnerary[4, 61]. The plant once had a very high reputation as a healer of wounds[4]." [PFAF]

Cultivation & Propagation

"Succeeds in ordinary garden soil[1, 200]. Prefers a well-drained fertile soil and a sunny position[200]. Tolerates dry, low fertility and alkaline soils[200]. Established plants are tolerant of considerable neglect, thriving and even self-sowing in dense weed growth[K]. Members of this genus are rarely if ever troubled by browsing deer[233]." [PFAF]

"Seed - sow April in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and plant them out into their permanent positions in the summer. Division in autumn. Very easy, larger clumps can be replanted direct into their permanent positions, though it is best to pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the summer or following spring. This should be done at least once every three years in order to maintain the vigour of the plant. Basal cuttings in spring. Harvest the shoots when they are about 10 - 15cm long with plenty of underground stem. Pot them up into individual pots and keep them in light shade in a cold frame or greenhouse until they are rooting well. Plant them out in the summer." [PFAF]

References


Centaurea nigrescens - short-fringed knapweed

"General: Perennial herb from a taproot; stems erect, branched, glabrous or somewhat sparsely long-hairy, 0.4-1.0 m tall." [IFBC-E-flora]

"Leaves: Basal leaves oblanceolate to elliptic, base tapering into the stalk, deeply to shallowly lobed or irregularly pinnately cut, glabrous or often lightly hairy below, up to 15 cm long and 3 cm wide; stem leaves lanceolate, unstalked, reduced upwards." [IFBC-E-flora]

"Habitat / Range Mesic roadsides and fields in the lowland zone; rare in SW BC (Saanich Peninsula, Vancouver Island) and SC BC (Mara Lake area); introduced from Europe." [IFBC-E-flora]

Status: Exotic [E-flora]

Synonyms

References


Centaurea stoebe - spotted knapweed

"General: Biennial or sometimes perennial herb from a taproot; stems erect, ridged, laxly branched, 0.2-1.8 m tall." [IFBC-E-flora]

"Leaves: Basal leaves pinnately cut, linear, stalked; stem leaves becoming reduced and unstalked above." [IFBC-E-flora]

"Notes: This species is sometimes difficult to separate from the closely related C. paniculata. The latter, however, has much stiffer, divergent branches that are often again branched with narrower heads." [IFBC-E-flora]

"Habitat / Range Dry roadsides and fields in the steppe and montane zones; frequent in S BC east of the Coast-Cascade Mountains; introduced from Eurasia." [IFBC-E-flora]

Status: Exotic [E-flora]

References


Centaurea x moncktonii - meadow knapweed

"General: Perennial herb from a taproot; stems erect, branched, thinly hairy, 40-80 cm tall." [IFBC-E-flora]

"Leaves: Basal leaves oblanceolate to lanceolate, simple to irregularly pinnately cut or with a wavy margin, sparsely long-hairy above, long-hairy below, soon deciduous; stem leaves similar, reduced upwards." [IFBC-E-flora]

"Habitat / Range Mesic to dry fields and waste places in the lowland, steppe and montane zones; infrequent in S BC south of 56degreeN; introduced from Europe." [IFBC-E-flora]

Status: Exotic [E-flora]

Synonyms

References


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