Pickerelweed & gooseweed (Monochoria & Sphenoclea)
Two broadleaf weeds that root in the mud and grow up through standing water in rice fields, controlled the same way.
- Type
- Broadleaf weeds (two species, grow together in water)
- Life cycle
- Annual; germinate and grow fast in standing water
- Spreads by
- Seed, carried easily by standing and flowing water
- Main harm
- Compete with rice for nutrients and light in wet fields
Overview
Monochoria vaginalis (pickerelweed) and Sphenoclea zeylanica (gooseweed) are two broadleaf weeds that grow together in the standing water of rice fields. Pickerelweed has shiny, heart- or arrow-shaped leaves on long stalks rising out of the water, with small blue-purple flowers. Gooseweed is an upright plant with a thick, hollow, spongy stem and small spikes of tiny white or pale pink flowers at the tip.
Both root in the mud and grow up through standing water, so they are most common in transplanted, low-lying rice fields that hold water well. Both grow fast in warm, wet conditions and can flower within a few weeks of germinating, so an uncontrolled patch spreads quickly within the same season if left alone.
How to identify it
- Pickerelweed (Monochoria vaginalis): shiny, heart- or arrow-shaped leaves on long stalks rising out of the water, with small blue-purple flowers.
- Gooseweed (Sphenoclea zeylanica): an upright plant with a thick, hollow, spongy stem and small spikes of tiny white or pale pink flowers at the tip.
- Both root in the mud and grow up through standing water, so they are most common in transplanted, low-lying rice fields that hold water.
- Both grow fast in warm, wet conditions and can flower within a few weeks of germinating.
Why it is a problem
- Both compete strongly with rice for nutrients, light and space in standing water, where they have an easy start.
- A thick stand of either weed can shade young rice tillers (young side-shoots) and reduce their growth.
- They flower and set seed quickly, so an uncontrolled patch spreads fast within the same season.
- Their seed survives in the mud and re-infests the field in later seasons if not controlled.
Cultural & preventive control
- Good land levelling helps prevent the low, wet pockets where both weeds establish first.
- Draining and drying the field for a short period, where the crop stage allows it, checks their growth, since both need standing water to thrive.
- Use clean, weed-seed-free irrigation water where possible, since seed travels easily in flowing water.
- Hand-pull or hand-cut small patches early, before they flower, to stop them from spreading seed through the field water.
Herbicide control
- A pre-emergence herbicide such as pretilachlor or butachlor, applied within 3 days of transplanting, checks the first flush of both weeds along with grasses.
- A post-emergence broadleaf herbicide such as 2,4-D or bispyribac-sodium (which also controls many grasses and sedges in the same spray) is effective on both.
- Spray when the weeds are small for the best result, and maintain the recommended water level before and after spraying as per the label.
- Confirm the current recommended herbicide and timing for your area with your local KVK.
Integrated management
- Combine good land levelling, water management, a pre-emergence herbicide, and a post-emergence herbicide rather than one spray alone.
- Since both weeds need standing water to establish, careful water management is one of your strongest tools against them.
- Remove any surviving plants by hand before they flower, so the seed left in the field does not build up for the next season.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
What are these two broadleaf weeds growing in the standing water of my rice field?
If you see shiny, heart- or arrow-shaped leaves on stalks rising out of the water with small blue-purple flowers, that is pickerelweed (Monochoria vaginalis). If you see an upright plant with a thick, hollow stem and small white or pale pink flower spikes, that is gooseweed (Sphenoclea zeylanica). Both are common broadleaf weeds of wet, transplanted rice fields, root in the mud, and are controlled the same way — a pre-emergence herbicide, a post-emergence broadleaf herbicide, and good water management.
Why do these weeds grow so thickly in the wetter parts of my field?
Both pickerelweed and gooseweed root in the mud and need standing water to establish and grow well, so they show up thickest in low-lying, wet pockets of a rice field — places where water collects or drains poorly. Levelling the field well and managing water levels evenly reduces the wet pockets where they get their first foothold.
Will my normal rice weed spray control both of these together?
Usually yes. A pre-emergence herbicide like pretilachlor or butachlor applied within 3 days of transplanting, followed by a post-emergence broadleaf herbicide like 2,4-D or bispyribac-sodium, controls both pickerelweed and gooseweed along with many grasses and sedges in the same programme. Spray while the weeds are still small, keep the field at the recommended water level as per the label, and confirm the exact product and timing for your area with your local KVK.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.