Flower:

Flowers are about ¼ inch across with 5 oval petals, white to light pink with darker lines radiating from the base. Flowers are single (rarely 2) on 2 to 3-inch hairy stalks from the upper leaf axils of growing branches. New flowers develop continuously through the growing season. The 5 sepals are oval-elliptic with a conspicuous sharp awn at the tip and spreading hairs on the outer surface; including the awn, they are about as long as or slightly longer than the petals.

Leaves and stems:

Leaves are mostly opposite and simple on a hairy stalk up to 2 inches long, deeply cleft into 3 to 5 palmate, lance-elliptic, sharply pointed lobes, 2 to 2½ inches across, with sparsely hairy surfaces and coarsely toothed edges.

At the base of a leaf stalk is a pair of long, narrowly triangular, leafy appendages (stipules). Stems are spreading to 3 feet across, ascending at the tips, densely hairy, and may be tinged red.

Fruit:

 Fruit is an erect capsule-like structure ½ to 1 inch long with the persistent sepals around the base. In the center is a slender column divided into five sections, each attached at its base to an oval shaped carpel containing a single seed. 

As the column drys and splits apart along its seams, the carpels are sprung upward, ejecting the seeds outward.

Notes:

Siberian Cranesbill is one of several non-native geraniums found in the US but the only one so far recognized as established in Minnesota. It is far less common than the native Bicknell's Cranesbill (Geranium bicknellii), with which it most likely to be confused. G. sibiricum can be identified by its more densely hairy stem, broader, more sharply pointed leaf lobes, and by typically having only a single, long-stalked flower in each leaf axil. While it is noted in some references as attaining heights up to 3 feet, we're not sure if this means it demonstrates this habit in other regions with warmer and longer growing seasons or if this only refers to its breadth of sprawl. Of the few specimens we've observed in Minnesota, unless supported by surrounding vegetation, Siberian Cranesbill rarely ascends much beyond 6 to 10 inches on open soil. We suspect this is another under-reported weed in Minnesota. All of these images came from a plant found along a roadside in Goodhue County that had been mowed over (probably several times). We transplanted it into our own yard to better ensure we could get sufficient images, then it was destroyed. For all we know it has now been eradicated from Goodhue County. :-)