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Oriental lady's thumb
Also known as: Asiatic smartweed
Oriental lady's thumb is a native of Asia and in that region it is a common weed in the rice paddies. Oriental lady's thumb can also be found in Europe and North America, where it is also considered a weed. It thrives in moist, wet soil such as floodplains, marshes, mudflats, and levees.
Scientific classification
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Weeds
Weed or not
Annual, Perennial
Lifespan
Herb
Plant Type
Summer, Fall
Bloom Time
Mid summer, Late summer, Early fall
Harvest Time
30 cm to 1.02 m
Plant Height
30 cm to 90 cm
Spread
Green, Blue
Leaf Color
3 mm to 7 mm
Flower Size
Black
Fruit Color
Pink, White, Purple, Red
Flower Color
Green, Red
Stem Color

Images of Oriental lady's thumb

Distribution of Oriental lady's thumb

Distribution Map
Oriental lady's thumb is native to pastures and disturbed land in central and eastern Asia and has been widely introduced in the eastern USA. This plant grows aggressively, colonizing disturbed ground, and it is classed as an invasive species in five US states.
Native
Cultivated
Invasive
Introduced
No species reported
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Habitat
Wet grassy places and valleys, along streambanks, shaded places along ditches, water sides
Hemisphere Trend Curve

Culture

Garden Use
Oriental lady's thumb can be an adaptive addition to outdoor gardens as it can tolerate many conditions regarding sun, soil, and water requirements. Grown for its pink, showy flowers which emerge any time from summer to early fall, this plant is a colorful addition to backyard gardens.
Symbolism
Dependency
Interesting Facts
This plant was found in Philadelphia around 1910. It is a kind of rice field weed that is hard to remove because of its strong viability in wetlands, river banks, grasslands, moors and mudflats.
Name Story
Asiatic smartweed: This plant is called smartweed because it has a sharp, peppery flavor and it secretes saps that bring tears to one's eye. As it is also originated from Asia, so it is called Asiatic smartweed.
Oriental lady's thumb: The latin genus name Persicaria, refers to the swollen nodes on the jointed, slightly angled stems. This plant grows flowers that vary from light rose or dull pink to whitish-green. This color varying plant is similar to the lady's thumb except for the flower color, so it is called oriental lady's thumb.
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Weed Control

The oriental lady's thumb is a weed native to China, Japan, India, Malaysia, and Korea. It is considered an invasive weed in the New England states of Connecticut, Maine, Massachusetts, New Hampshire, and Vermont. The species roots in wet, disturbed habitats such as gardens, streambanks, or railroad margins. Little research has been done on its environmental effects, but it has been suggested that the weed displaces native species. This weed is a source of food for animals such as songbirds and beetles. The oriental lady's thumb is edible and resistant to control methods such as mowing. The weed should instead be controlled using chemical herbicides.
How to Control It
The best season for removing oriental lady's thumb is during late spring or early summer. This is when the plant is actively growing but before it has a chance to flower and produce seeds. You want to remove the plant before it reaches its seed-producing stage to prevent it from spreading.
  1. Hand-pulling: Put on a pair of gardening gloves to protect your hands, then grab the base of the weed and pull it up. Try to remove as much of the root system as possible to prevent the weed from regrowing.
  2. Hoeing: Use a sharp hoe to cut the weed off at ground level. This method is best for larger areas that are infested with oriental lady's thumb. Make sure to hoe regularly as new weeds emerge.
  3. Smothering: Cover the area with a thick layer of straw, leaves, or other organic material. This will block sunlight and prevent the weed from growing. Leave the material in place for at least one growing season to ensure all weed seeds are killed.
  4. Organic herbicides: Apply an organic herbicide to the weed. Many organic herbicides are non-selective, meaning they kill all plants they come into contact with, so use caution when applying.
  5. Digging: If the weed is deeply rooted, use a gardening fork or spade to dig around the weed, making sure to remove as much of the root system as possible. Fill the hole with soil and replant with desired plants.
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Care Guide for Oriental lady's thumb

Every week
Water
Full sun
Sunlight
20 - 35 ℃
Ideal Temperature
Water: Oriental lady's thumb prefers consistently moist environments, requiring weekly watering for optimal health. Though adaptable, it can survive brief dry periods. Thriving in outdoor settings near water bodies, oriental lady's thumb's growth is closely linked to water availability, flourishing when properly hydrated.
Propagation: Oriental lady's thumb propagates well by sowing in Spring, the optimal season. The process is moderately easy, indicated by healthy seedling emergence. It's crucial to maintain proper soil moisture and ensure adequate spacing between seeds for successful growth.
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