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The tips of the upper stems of heartleaf alexanders produce 2-3" wide compound umbels of 7-15 umbellets, each with 10-20 tiny yellow flowers. The central flower of each umbellet is sessile; the rest have short pedicels (a diagnostic character of the genus). Each 1/8" wide flower consists of five yellow petals that remain curled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed capsule with a flat top from which the remnants of the styles project. Heartleaf alexanders is restricted to northeastern Illinois, where it is uncommon; it is usually found in drier habitats than its much more common relative, golden alexanders (Zizia aurea).

Zizia

Zizia aptera

heartleaf alexanders [Blooms: Apr/May–?]

The tips of the upper stems of golden alexanders produce flat to slightly rounded compound umbels 2-3" across with about a dozen umbellets of tiny, golden-yellow flowers. Each umbellet has about 20 flowers; the central flower is sessile (or nearly sessile) while all the other blooms in the umbellet are on short stalks (pedicels), a character of the genus. Each 1/8" wide flower consists of an insignificant calyx, five yellow petals that are persistently incurled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed (not winged) 2 mm long capsule with a flat top from which the remnants of the two styles project. Golden alexanders prefers full to partial sun and is tolerant of a range of habitat quality. The yellow-flowered variety of meadow parsnip (Thaspium trifoliatum var. aureum) is very similar to golden alexanders but has basal leaves that are simple rather than trifoliate compound, but I have not seen meadow parsnip in Jackson Park. John Hilty (www.illinoiswildflowers.info) warns that "Golden Alexanders should not be confused with Pastinaca sativa (Wild Parsnip), which is a weedy Eurasian biennial. The latter is taller, blooms later, and has more leaflets in each compound leaf." Wild parsnip DOES occur in Jackson Park, but it is relatively rare, twice the size of golden alexanders, has robust, strongly ribbed stems, and a large, flattened, winged fruit. Heartleaf alexanders (Zizia aptera) is also very similar, but only the uppermost leaves are compound; all the lower and middle leaves are simple and heart-shaped.

Zizia

Zizia aurea

golden alexanders [Blooms: Apr/May–?]