Baccharis thesioides
Baccharis halimifolia
Arizona baccharis, Mogollon baccharis
consumption-weed, eastern baccharis, eastern false willow, sea-myrtle
erect to ascending, slender, striate-angled, glabrous, scarcely resinous.
erect to ascending, slender, striate-angled, glabrous or minutely scurfy, sometimes resinous.
usually present at flowering;
sessile;
blades (1-nerved) linear-oblanceolate to narrowly oblong, 20–40(–80) × 4–8 mm, bases cuneate, margins evenly serrate (teeth spinulose, apices acute, faces finely gland-dotted, not resinous).
present at flowering; short-petiolate or sessile;
blades elliptic to broadly obovate or rhombic, main cauline rhombic, 30–50(–80) × 10–40(–60) mm (thick and firm), bases cuneate, margins entire proximally, usually coarsely serrate distal to middles (teeth 1–3 pairs), faces glabrous, gland-dotted, resinous (distal reduced, entire).
campanulate; staminate 3–6 mm, pistillate 3–6 mm.
campanulate; staminate 3–5 mm, pistillate 3–5 mm.
30;
corollas 2.2–3 mm.
20–30;
corollas 2.5–3.5 mm.
20–30;
corollas 3 mm.
25–30;
corollas 3–4 mm.
lanceolate, 1–5 mm, margins scarious, erose-ciliate, medians green, apices acute or obtuse (erose, abaxial faces glabrous).
ovate to lanceolate, 1–4 mm, margins scarious, medians green, apices obtuse to acute.
(10–50+) in terminal, compact, rounded paniculiform arrays.
3–4 in loose pedunculate clusters in (terminal, leafy-bracted) broad paniculiform arrays.
1.5–2.2 mm, 5-nerved, glabrous;
pappi 4–6 mm.
1–1.8 mm, 8–10-nerved, glabrous;
pappi 8–12 mm.
= 18.
Baccharis thesioides
Baccharis halimifolia
Baccharis thesioides is recognized by its erect stems, narrow, oblong, evenly serrate leaves with finely spinulose teeth, heads in relatively small rounded arrays, and 5-ribbed cypselae with short pappi. It is sometimes confused with B. bigelovii, which has broader and irregularly serrate leaves. The two taxa may belong to the same species complex centered in Mexico.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Native to the Atlantic and Gulf Coastal Plain, Baccharis halimifolia is recognized by its broad, distinctly rhombic, coarsely serrate basal leaves, pyramidal, leafy arrays, and cypselae with large fluffy pappi. The plants are often to 600 cm; the basal leaves might be missed by collectors. Forms with relatively narrow leaves are especially common in Arkansas, Louisiana, and east Texas. These may be the result of hybridization and introgression with B. neglecta, in areas where they are known to hybridize (D. J. Zanowiak 1991), or with B. angustifolia. Hybrids between B. halimifolia and B. angustifolia are known from Florida as well. Baccharis halimifolia has been introduced to Australia and France. In Australia it infests large areas along the coast of southern Queensland and New South Wales. Its success as an invasive weed is attributed to production of a large number of seeds that are widely dispersed by the wind, shade tolerant germination and seedlings, tolerance to wet soils and salinity, and ability to resprout after a fire (W. E. Westman et al. 1975). The leaves of B. halimifolia contain a cardiotoxic glycoside known to cause the death of sheep if they eat about one percent of their body weight in leaves.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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