Small-flowered Tonella is a small annual with spindly, erect or ascending stems from 5-25 cm high. The thin, weak stems are often branched and tend to be glabrous throughout. The small leaves tend to be less than 2 cm long. The basal leaves are are petiolate with rounded blades. The lower stem leaves are often trifoliate. The upper pairs of stem leaves are reduced in size and narrowly ovate with 3 shallow lobes or rounded teeth on the distal half of the blade.
The minute flowers arise singly from the upper leaf axils or leaf-like upper bracts. The thin pedicels are long 5-12 mm long and slightly down-turned at the tips. The calyx is1.5-2 mm long with 5 ciliated lobes equalling the length of the calyx tube. The corolla measures 2-3 mm long with the spreading lobes, the lowermost lobe the largest. Pale lilac mottling or spots may be found on the inner surface of the whitish corolla or onto the lobes. The fruit is a globose capsule that is longer than the calyx.
Small-flowered Tonella may be found from low to medium altitudes on moist rocky soils. It is often found beneath Oregon white oak.
Small-flowered Tonella may be found in the Columbia River Gorge from near The Dalles and westward and then south through the Willamette Valley to central California. It may also be found in the lowlands along major tributaries leading to the Columbia River in southwestern Washington.
In the Columbia River Gorge it may be found between the elevations of 100-2500' from east of Angels Rest eastward to the western Columbia Hills to the north of The Dalles.