When I first noticed Virginia Knotweed, I thought the flowers never opened very wide, but stayed as these half moon, white bits on a long, dark cord. The flowers are small and easy to ignore. One day I noticed a flower looked different and found this plant has lovely, small, white flowers.
Persicaria virginiana Gaertn.
June to October N Family: Polygonaceae
Flower: White flowers are spaced out along the end of the stem which has thinned to form a tough cord. Each flower is small, a quarter of an inch across, with four petals, four stamens and two pistils. They open a few at a time in a generally base to tip order.
Leaf: Alternate leaves are dark green on top and lighter on the underside. The lower leaves have petioles that become shorter as the leaves are higher on the stem. The leaves are thick with a strong midvein, covered sparsely with short hairs. They have smooth edges and are broadest in the middle and taper to a sharp point.
Stem: The green stems can reach four feet long, half of which is lined with flowers. They start growing up but the flowering portion arches over. Each leaf node is wrapped with a thin tissue surrounding the petiole base and the stem. This is tan and papery. It has several long bristles that stick up from the top lying along the stem. The stem and the rest of the ligule are covered with short hairs.
Root: The perennial root puts out rhizomes producing clumps of plants.
Fruit: The flower closes to form a half moon, eighth of an inch long, dark brown seed capsule. The pistils persist turning stiff and hard with a curved tip making a beak.
Habitat: This plant likes growing in the shade in moister areas such as roadsides near ravines and ditches, stream banks, low woods and bluff bases.
Virginia Knotweed is a late grower along the roads. Once it gets started, it forms masses of large leaves up to six inches long.
The long flower stalks are very thin, like dark, stiff string. The flowers look like little, white beaks scattered along its length. Since they have this shape both before and after blooming, an open flower can be a surprise.
The flowers are small, but a lovely, glistening white. They open for a day, then close.
Once the seeds form, the long stems show their usefulness. They move in any breeze, even that created by a passing creature. The seed beaks stab into fur or cloth. The seeds seem to jump off the stem to get carried off. This is the source of one common name.
The plant favors shady spots. It is difficult to photograph as the flower stems are so thin and the flowers so small. These disappear into the background unless it is a solid, dark one like a stump.
The plants grow from rhizomes so they tend to grow in colonies. The colonies get larger each year as the roots are perennial. This can leave an area thick with the plants shading out other wildflowers and grasses, although taller plants like goldenrod grow up through them.