Flower:

Slender, elongating spike at the tip of branching stems, the flowers arranged alternately, 1 or 2 per node, crowded and strongly overlapping for most of the spike. Flowers are tiny, petal-less, have 5 stamens and 2 or 3 styles. The bracts surrounding the flower are green, erect to ascending, more or less egg-shaped, tapering to a white spine at the tip.

Leaves and stems:

Leaves are mostly alternate, thread-like to narrowly linear, up to ~2 inches long, 1 to 2 mm wide, nearly round in cross-section, widened and stalkless at the base, and have a short white spine at the tip. Edges are toothless, surfaces are hairless but often have sparse, tiny bristles. Stems are single, hairless to sparsely hairy, ridged, green or red-striped, usually erect, usually many-branched above the base, often becoming bushy and the whole plant turning red later in the season.

Fruit:

Fruit is a brown, cup-shaped, 1-seeded capsule with or without a narrow, notched wing around the top, 2 to 5 mm in diameter including any wing. At maturity the plant breaks off at ground level and becomes a tumbleweed, spreading 1000s of seeds as it goes.

Notes:

The first report of Slender Russian Thistle in North America was by Minnesota's own John Moore, collected from a Dakota County roadside in 1937. A weed from Eurasia, it is most often found in the usual places where weeds congregate—roadsides, railroad rights-of-way, gravel pits, empty lots and other waste places—but it's also been known to creep into higher grade prairies and rock outcrops. It likes dry, sandy soil.

It is often mistaken for its much more common cousin, Russian Thistle (Salsola tragus), and is no doubt under-reported in the state. Both have thread-like leaves with a spiny tip. S. tragus is distinguished by fruit with a wide wing around the top, spikes that are more loosely arranged, the flowers not strongly overlapping except towards the tip, and floral bracts that are widely spreading. Pretty much every reference notes the bracts of S. collina are appressed where S. tragus are spreading, but this caused me some confusion in the field. The base of S. collina bracts are more or less erect, tightly hugging the flower, but the tips tend to flare out so they appear to be more ascending than appressed. This should still adequately separate it from S. tragus, where the bract base can be perpendicular to the stem or nearly so, plus the density of the spike (crowded or loose).