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Vascular Plants of California
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Centaurea melitensis
TOCALOTE; MALTESE STAR-THISTLE


Higher Taxonomy
Family: Asteraceae (Compositae)View DescriptionDichotomous Key
Common Name: SUNFLOWER FAMILY
Habit: Annual to tree. Leaf: basal and/or cauline, alternate, opposite, rarely whorled, simple to 2+ × compound. Inflorescence: 1° inflorescence a head, resembling a flower, of several types (see below), 1--many in generally +- cyme-like cluster; each head generally with +- calyx-like involucre of 1--many series of phyllaries (involucre bracts); receptacle of head flat to conic or columnar, paleate (bearing paleae = receptacle bracts) or epaleate; flowers 1--many per head. Flower: bisexual, unisexual, or sterile, +- small, of several types (see below); calyx 0 or modified into +- persistent pappus of bristles, scales, and/or awns; corolla radial or bilateral (0), lobes generally (0)3--5; stamens 4--5, filaments generally free, generally fused to corolla at tube/throat junction, anthers generally fused into cylinder around style, anther base generally rounded or cordate (deeply sagittate or with tail-like appendages), tip (= flattened appendage) generally projecting beyond pollen sac; pistil 1, 2-carpeled, ovary inferior, 1-chambered, 1-seeded, placenta basal, style 1, tip generally +- 2-branched (except in some staminate disk flowers), branch tips truncate or generally bearing +- brush-like appendages; stigmas 2, generally on adaxial faces of style branches. Fruit: achene (also called a cypsela) (drupe in Chrysanthemoides), cylindric to ovoid, sometimes compressed, generally deciduous with pappus attached.
Genera In Family: +- 1500 genera, 23000 species: worldwide, many habitats. Note: Flower and head types differ in form and sexual condition. A disk flower has a generally radial corolla, with a cylindric tube, expanded throat, and generally 5 lobes. Disk flowers are generally bisexual and fertile but occasionally staminate with reduced ovaries. Discoid heads comprise only disk flowers. A radiant head is a variant of a discoid head, with peripheral disk flower corollas expanded, often bilateral. A ray flower corolla is bilateral, generally with a slender tube and flattened petal-like ray (single lip composed of generally 3 lobes). Ray flowers are generally pistillate or sterile (occasionally lacking styles). Radiate heads have peripheral ray flowers and central disk flowers. Disciform heads superficially resemble discoid heads, with pistillate or sterile flowers that lack rays, together with or separate from disk flowers. A ligulate flower is bisexual, with a bilateral, generally ephemeral corolla and 5-lobed ligule. Liguliflorous heads comprise only ligulate flowers. See glossary p. 31 for illustrations of family characteristics. Echinops sphaerocephalus L., Gaillardia aristata Pursh, Gaillardia pulchella Foug., Hymenothrix loomisii S.F. Blake, Tagetes erecta L., Thelesperma megapotamicum (Spreng.) Kuntze are waifs. Melampodium perfoliatum Kunth, historic urban waif. Ageratum conyzoides L., Guizotia abyssinica (L. f.) Cass., Santolina chamaecyparisus L., orth. var. are rare or uncommon escapes from cultivation. Dyssodia papposa, Ismelia carinata (Schousb.) Sch. Bip. [Chrysanthemum carinatum Schousb.], Mantisalca salmantica (L.) Briq. & Cavill. are historical or extirpated waifs in California. Inula helenium L. not documented in California. Taxa of Aster in TJM (1993) treated here in Almutaster, Eucephalus, Eurybia, Ionactis, Oreostemma, Sericocarpus, Symphyotrichum; Chamomilla in Matricaria; Bahia in Hymenothrix; Cnicus in Centaurea; Conyza in Erigeron and Laennecia; Dugaldia in Hymenoxys; Erechtites in Senecio; Hymenoclea in Ambrosia; Lembertia in Monolopia; Osteospermum ecklonis in Dimorphotheca; Picris echioides in Helminthotheca; Prionopsis in Grindelia; Raillardiopsis in Anisocarpus and Carlquistia; Schkuhria multiflora in Picradeniopsis; Trimorpha in Erigeron; Venidium in Arctotis; Whitneya in Arnica. Amauriopsis in TJM2 (2012) treated here in Hymenothrix; Arida in Leucosyris; Bahia in Picradeniopsis.
Unabridged Note: Largest family of vascular plants in California and of eudicots globally.
eFlora Treatment Author: David J. Keil, except as noted
Scientific Editor: David J. Keil, Bruce G. Baldwin.
Genus: CentaureaView DescriptionDichotomous Key


Common Name: KNAPWEED, STAR-THISTLE
Habit: 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.
Species In Genus: +- 500 species: especially Eurasia, northern Africa; some cultivated. Etymology: (Greek: plant name associated with Chiron, a centaur) Note: Many noxious or invasive weeds. Centaurea nigrescens Willd. not naturalized.
eFlora Treatment Author: David J. Keil
Reference: Keil & Ochsmann 2006 FNANM 19:181--194
Centaurea melitensis L.
NATURALIZED
Habit: Annual 1--10 dm, +- gray-hairy, resin-dotted. Stem: generally 1, distally +- branched, winged. Leaf: +- thinly tomentose, +- scabrous, and puberulent with short, crinkled hairs; proximal 2--15 cm, entire to lobed, often 0 at flower; distal cauline entire or toothed, long-decurrent. Inflorescence: heads disciform, 1--many, peduncled (or sessile in axils), sometimes of cleistogamous flowers; involucre 10--15 mm, ovoid, +- cobwebby or becoming glabrous; main phyllaries +- straw-colored; tip appendage +- purple, base spine-fringed, central spine 5--10 mm, slender. Flower: many; corolla yellow; sterile flower corolla +- = disk; disk flower corolla 10--12 mm. Fruit: +- 2.5 mm, +- light brown, finely hairy; pappus bristles 2.5--3 mm, white. Chromosomes: 2n=18,24,36.
Ecology: Disturbed fields, open woodland; Elevation: < 2200 m. Bioregional Distribution: CA-FP, D (uncommon); Distribution Outside California: native to southern Europe. Flowering Time: Apr--Jul
Jepson eFlora Author: David J. Keil
Reference: Keil & Ochsmann 2006 FNANM 19:181--194
Jepson Online Interchange
Noxious Weed listed by CDFA
Weed listed by Cal-IPC

Previous taxon: Centaurea jacea nothosubsp. pratensis
Next taxon: Centaurea pouzinii

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Citation for this treatment: David J. Keil 2012, Centaurea melitensis, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=1934, accessed on October 20, 2019.

Citation for the whole project: Jepson Flora Project (eds.) 2019, Jepson eFlora, http://ucjeps.berkeley.edu/eflora/, accessed on October 20, 2019.

Centaurea melitensis
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© 2012 Neal Kramer
Centaurea melitensis
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© 2013 Neal Kramer
Centaurea melitensis
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© 2007 Neal Kramer
Centaurea melitensis
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© 2007 Thomas Stoughton
Centaurea melitensis
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© 2008 Keir Morse
Centaurea melitensis
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© 2010 Neal Kramer

More photos of Centaurea melitensis in CalPhotos



Geographic subdivisions for Centaurea melitensis:
CA-FP, D (uncommon)
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Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time.