Ontario Weeds: Petty spurge
Excerpt from Publication 505, Ontario Weeds,
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Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Petty spurge, inflorescence viewed from side.
Stems & Roots: Stems erect, 10-30cm
(4-12in.), single or branched from the base; top of each main stem
3-branched at base of inflorescence; lower and middle stem leaves
alternate (1 per node), oblong to rounded, 1-2cm (2/5-4/5in.) long,
short-stalked; leaves at tip of stem in one whorl of 3 leaves from
the same node; leaves opposite (2 per node) in the inflorescence.
Flowers & Fruit: Inflorescence beginning as a 3-branched umbel and branching repeatedly in 2's, with a small flower cluster, in the angle between each pair of branches; flowers complex in cyathia or tiny cups, like those described for Leafy spurge; seedpods 3-lobed, containing 3 seeds; seeds about 1.5mm (1/16in.) long and about half as wide, somewhat 6-sided, the 2 inner faces with long, narrow depressions, the 4 outer surfaces with 2 to 4 circular depressions, gray to gray-brown. All parts contain a white milky juice which freely exudes when the plant is cut or broken. Flowers from early July until end of fall.
Habitat: Petty spurge occurs throughout southern Ontario in gardens, waste areas, roadsides and occasionally in cultivated fields.
Similar Species: It is distinguished from other erect-growing spurges by its annual habit, by the combination of alternate leaves on main stem, whorl of 3 leaves at tip of stem, and pairs of smaller opposite leaves in the inflorescence, by its main umbel at the tip of the stem having only 3 branches, and by its small, elongated, gray to brownish, 6-sided seeds with 2 elongated depressions and 4 rows of 2 to 4 rounded depressions. There is also a tendency for the stems to be somewhat succulent, and for the 3 main branches of the inflorescence to be somewhat enlarged above the nodes and taper upwards to be much thinner just below the next pair of small leaves.
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