Prickly Sida
Sida spinosa
Mallow family (Malvaceae)

Description: This plant is a summer annual that becomes –2' tall, branching occasionally. The stems are covered with fine white hairs. The alternate leaves are up to 2" long and 1" across. They are ovate or ovate-oblong, crenate along the margins, and sparsely covered with fine hairs that are difficult to see. These leaves have long petioles (up to 1" long) and are rounded or slightly cordate at the base. At the base of the petiole, there is a pair of linear stipules; some of the lower leaves also have a blunt green spine below the base of their petioles.

One or a few flowers develop from the axils of the leaves on short peduncles (flowering stalks) up to " long. These peduncles are shorter than the petioles, which causes the flowers to appear hidden among the leaves. Each flower is about 1/3" (8 mm.) across when fully open; it consists of 5 spreading petals that are light yellow or light orange, 5 sepals that are green and broadly lanceolate, and a united column of 5 styles and numerous stamens that becomes spreading at its apex. The petals are well-rounded and rather floppy; there are pale lines across their upper surface that function as nectar guides. The blooming period occurs from mid-summer to early fall and lasts about 1-2 months for a colony of plants. The flowers usually bloom during bright sunny mornings. Each flower is replaced by circular seedpod with 5 brown segments that break apart. Each segment encloses a single seed and has 2 spreading spines at its apex. The seeds are reddish brown and 3-angled. The root system consists of a shallow taproot that divides into secondary roots. This plant spreads by reseeding itself, and it occasionally forms colonies.

Cultivation: Typical growing conditions are full or partial sun and moist to mesic soil that is loamy and fertile. Once the seeds germinate, this plant develops very quickly.

Range & Habitat: Prickly Sida is fairly common in southern and central Illinois, but absent from the NW and north central areas of the state. This plant is probably adventive from tropical America, although some authorities think it is native to some areas of the United States, including the lower Midwest. The northern boundary of its range at the time of European settlement is not entirely clear. Habitats include cropland, abandoned fields, gardens, grassy areas along railroads and roadsides, and waste areas where the soil has been recently disturbed. This is primarily a weed of fields and gardens that is rarely observed in high quality natural habitats.

Faunal Associations: The flowers attract various bees, including bumblebees, little carpenter bees, and Halictid bees, as well as small to medium-sized butterflies and skippers. Charles Robertson observed the following Lepidopteran species on the flowers of Prickly Sida: Colias philodice (Clouded Sulfur), Eurema lisa (Little Yellow), Pieris rapae (Cabbage White), Pontia protodice (Checkered White), and Pyrgus communis (Common Checkered Skipper). The foliage is not known to be toxic and it may be eaten occasionally by mammalian herbivores. These animals help to distribute the seeds as the spines on the segments of the seedpods can cling to either fur or clothing.

Photographic Location: An abandoned garden at the webmaster's apartment complex in Urbana, Illinois.

Comments: At first glance, this leafy plant does not appear to be a member of the Mallow family, but a careful examination of the flowers reveals a united column of styles and anthers that is a typical characteristic of Mallow flowers. Prickly Sida is a rather unique plant that doesn't closely resemble other Mallows, which are either small weedy vines, tall wetland species with huge flowers, or plants with purple or pink flowers. A distinguishing characteristic of Prickly Sida is the blunt green spines that occur below the petioles of the lower leaves. The only other Sida sp. (Sida) in Illinois, Sida elliottii (Elliott's Sida), is confined to a few southern counties. It is a more conservative perennial species that occurs in sand prairies. Elliott's Sida has narrow leaves that are linear-oblong or oblong, and its yellow flowers are larger in size (–1" across) than those of Prickly Sida.