Persicaria

( per - sih - KAR - ee - ah )

At-A-Glance Information

Commonly referred to as Knotweed or Smartweed, this genus of flowering perennial plants needs full sun to partial shade and regular water to perform well. They are considered easy to grow and care for, and have handsome foliage. Flowers bloom in shades of pink or white. Some species tend to get a bit out of hand if not controlled, so they are best planted in areas where this tendency won't cause issues for other plant life. 

Persicaria Species and Varietals

The genus Persicaria is a member of the plant family Polygonaceae and includes 132 species. The genus was segregated from Polygonium. The best growing zones for Knotweed vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Persicaria amphibia (Longroot Smartweed, Water Knotweed, Water Smartweed, Amphibious Bistort)
These plants are native to much of North America, Asia, Europe, and some areas in Africa. It is considered a weed in some parts of the world. These plants prefer wet habitats, like ponds, streams, and marshes. They can be fully aquatic, growing submerged or floating in bodies of water. Flowers are typically in shades of pink.

Persicaria bicornis (Pink Smartweed)
These plants are native to areas in the central and southwestern United States, and is an annual planting that reaches up to 6 inches tall. Flowers are pink with pink or red anthers and are present from June through October. Blooms are fringed. Leaves are green and narrow. These plants typically grow in ditches or other disturbed areas, or along the shores of ponds and reservoirs.

Persicaria bungeana (Prickly Smartweed, Bunge's Smartweed)
These annuals are common weeds of soybean fields in the midwestern United States, and forms a small plant that reaches between 11 and 31 inches tall when mature. Leaves are pale green with a reddish tint, and flowers are pink to cream-white. It is native to China, Manchuria, Korea, and Japan.

Persicaria capitata (Polygonum capitatum) (Pink-Headed Persicaria, Pink Bubble Persicaria, Japanese Knotweed, Pink Knotweed, Pinkhead Smartweed)
Zones 8, 9 and 12-24, native to the Himalayas. This cool-weather loving plant forms a trailing groundcover 3-6 inches tall. Leaves are bronze when new, and mature to green blushed with pink. Stems and flowers are pink, and this plant will bloom year-round in mild climates. Best for containers, where it can't spread indefinitely and does not need irrigation.

Persicaria chinensis (Polygonium chinense) (Creeping Smartweed, Chinese Knotweed)
These plants are native to India, China, Japan, Indonesia, Malaysia, and Vietnam. It is used in its native range as a traditional medicinal plant. It is considered a weed in Australia. These perennial climbing plants reach between 6.5 and 10 feet tall when mature, and produces small white to pink flowers. Fruits that follow are edible but quite sour.

Persicaria decipiens (Slender Knotweed)
These trailing plants reach about a foot tall and have narrow spear-shaped green leaves. Flower spikes support pink flowers from November through June, peaking in February. Plants die back in wintertime and regenerate after the first rains. They are native to Australia and Asia.

Persicaria hydropiper (Polygonum hydropiper) (Arse Smart, Tade, Water Pepper, Marshpepper Knotweed)
These plants are widespread across Australia, New Zealand, Asia, Europe and North America, where they grow in damp areas and shallow waters. Some varieties are cultivated for culinary purposes; they have a pungent flavor (hence the common name Water Pepper). 

Persicaria lapathifolia (Polygonum lapathifolium) (Pale Persicaria, Pale Smartweed, Curlytop Knotweed, Willow Weed, Dock-Leaved Smartweed)
These variable species of Knotweed is native to most of the world, and is considered a weed in Europe. Stems are erect and reddish, holding tiny pink flowers. Foliage typically has darker markings towards the center of leaves. These plants are typically found growing on seashores and disturbed areas, such as gardens, agricultural lands, waste grounds, and roadsides.

Persicaria longiseta (Oriental Lady's Thumb, Bristly Lady's Thumb, Asiatic Smartweed, Long-Bristled Smartweed, Low Smartweed, Asiatic Waterpepper, Bristled Knotweed, Bunchy Knotweed, Tufted Knotweed)
These plants are native to Asia, and have been introduced to North America and Europe, where it is typically considered a weed. These annuals reach between 12 and 32 inches long, and have hairless, branching stems. Inflorescences reach up to 3.2 inches long and hold many small pink flowers.

Persicaria odorata (Vietnamese Coriander, Ram, Laksa Leaf, Vietnamese Cilantro, Phak Phai, Praew Leaf, Hot Mint, Cambodian Mint, Vietnamese Mint)
These plants have a general appearance and fragrance reminiscent of commonly used culinary herbs. They are used in Asian cuisines and to produce essential oils. They grow well in warm, damp conditions and reach up to 24 inches tall and wide. Tops of leaves are dark green with spotting, and undersides are burgundy-red. 

Persicaria orientalis (Kiss-Me-Over-The-Garden-Gate, Princess-Feather)
These plants are native to Eurasia, and is widely cultivated and naturalized in many places in the world. Leaves are simple and green, and flower inflorescences are somewhat drooping and various shades of pink. 

Persicaria perfoliata (Polygonum perfoliatum) (Mile-a-Minute, Devil's Tail, Giant Climbing Tearthumb, Asiatic Tearthumb)
This species forms a trailing herbaceous annual vine with barbed stems and triangular leaves. It is native to temperate and tropical areas of Asia. These are highly invasive weeds, and produce vining reddish stems and small white flowers. Fruits are edible and metallic blue. These plants are used in salads and soups.

Persicaria tinctoria (Chinese Indigo, Japanese Indigo, Dyer's Knotweed)
These plants are a source of indigo dye in many areas of Eastern Europe and Asia. They produce green leaves (the source of the dye). Flowers are bright pink with white bases, and stems are typically red.

Persicaria virginiana (Polygonum virginianum, Tivara virginiana) (Jumpseed, Virginia Knotweed, Woodland Knotweed)
This species is best in zones 2-9 and 14-17 and is native to the eastern areas of North America and Asia. It spreads by creeping rhizomes and is not commonly found in gardens. Variety 'Painter's Palette' is more common than the species and has marbled foliage, as does cultivar 'Variegata'.

Caring for Persicaria

Propagation

Problems and Pests

Gallery

Camellias are great candidates to be grown as container plants on your patio.
A field of thea sinensis
Camellia hiemalis 'Shishi Gashira'

Videos

A video all about growing camellias successfully
Propagating camellias

Resources

Wikipedia: Persicaria
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 494 - 495, Persicaria 
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