Fabaceae: Mimosa nuttallii
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Family Name
Fabaceae
Common Name
Sensitive brier
Description
Mimosa nuttallii is a sprawling perennial herb with stems that grow up to 1 m long, covered with small prickles, 0.5-2 mm long. The alternate leaves are bipinnate leaf blades are divided into four to nine pairs (pinnae), and each of these have 8–15 pairs of leaflets, 3-9 mm long with a prominent midrib visible on the upper pairs and stipules 4-6 mm long. The leaves exhibit nyctinastic movement, folding up quickly when touched. The inflorescence consists of axillary, many-flowered heads, with peduncles 3-9 cm long. The pink to lavender flowers are sessile, with a minute calyx. The 5 united petals form a narrow tube about 4 mm long and lobes of about 1 mm, with 8-12 stamens inside. The fruit is a legume, 3-12 cm long and covered with prickles and explodes upon drying expelling the seeds. Nuttall’s sensitive briar blooms from April into September on prairies, in ravines and in open woodlands in central South Dakota.
Synonym: Schrankia nutallii
Horticulture Notes
Seed Collection: Collect seed in July-September when pods turn brown. Place fruit in a paper bag to catch the seeds when the pods open.
Germination: Seeds are mildly dormant and germinate with scarification with sandpaper and a short (10-30 days) moist cold treatment. Fall sowing, without treatment produces good results.
Soils: Gravelly or sandy well drained soils.
Light: Full sun.
Water: Seeds and seedlings require a moist period become established but mature plants do best in dry conditions.
Additional Notes
Nuttall’s sensitive briar is a unique addition to a native plant garden. Its flowers are somewhat attractive to humans and native bees, but the plant forms mounds that can appear weedy. However, the leaves make it a plant of interest, especially to children because of the way the leaflets fold up when lightly touched and the whole leaf folds when struck with more force.