Sensitive brier has a lot going for it. The flashy flowers are bright pink, the foliage responds to your touch and it provides forage for wildlife. That’s a lot to like about this little trailing plant.
Latin Name/Common Name- The genus name Mimosa is Greek in origin and means “mimic”. Nuttallii honors Thomas Nuttall, the English botanist who studied plant life in the US in the 1800′s. The common name “Sensitive brier” was given because the leaves fold up when disturbed. It is also known as Devil’s shoestrings and Cat’s claw or Catclaw brier because of the prickles on the trailing stems.
Mimosa nuttallii is a perinnial in the legume (bean) family.
Bloom Color- There is nothing bashful about the blooms of Mimosa nuttallii. Each blossom is a globe composed of hot pink filaments with prominent yellow anthers at each tip.
Macro image of the pink filaments and two-lobed yellow anther
Description- Mimosa nuttallii is a creeping plant with a length of 4 to 5 feet. The stem is variably green or pink and is covered with recurved prickles.
The alternate leaves are bipinnately (twice pinnate) compound. This means that each leaf is divided into primary leaflets which are further divided into secondary leaflets.
This is one bipannately compound leaf of Mimosa nuttallii
Each of these is a primary leaflet arising from the leaf
This zoomed image is a secondary leaflet arising from a primary leaflet
Entire leaf Primary leaflet Secondary leaflet
The leaves of Mimosa nuttallii respond to various stimuli by folding along the primary leaflet. You can initiate this reaction simply by touching a leaf. The folding also may occur due to wind or darkness- the leaves fold up at night. This reaction is termed seismonasty and is quite common in the Mimosaceae family. You can read more about seismonasty in plants here- http://en.wikipedia.org/wiki/Thigmonasty.
The flowers of Mimosa nuttallii arise on long stalks at the leaf axils. Before blooming, the buds somewhat resemble green bramble fruits such as blackberry.
Trailing stem with flower buds in late May
Zoomed image of a single bud showing prickles on stem
Bloom Time- Mimosa nuttallii may be found in bloom from mid May to early September.
Habitat- Open fields and dry, rocky areas are preferred habitat for Sensitive briar. It is also seen growing at woodland margins.
Mimosa nuttallii thriving on dry, rocky ground
What’s Growing Nearby? Grasses and sedges are found growing alongside Mimosa nuttallii. I’ve also seen another interesting plant- Spider Milkweed (Asclepias viridis) thriving nearby in the same open field.
Mimosa nuttalli mixing with grasses in an open field
Spider milkweed growing alongside Sensitive brier
Endangered List- Fortunately, this fun little plant seems to be doing well within its range. It is not found on any state endangered list.
Interesting Tidbits- Mimosa nuttallii provides forage for deer and turkey. Bobwhite quail consume the seeds and the nectar is important for many insects. It is also nutritious for livestock; although, how they eat the briers, I don’t know. Nevertheless, its absence in a field is a good indicator of overgrazing.