Basilicum polystachyon: A Square Stemmed Weed in Rainfed Rice
Basilicum polystachyon is an upright broadleaf weed of the mint family that grows in rainfed lowland rice fields in the Philippines. Farmers may know it as pansi pansi. It can reach a meter tall and carries long spikes of lilac or pink flowers. This page shows how to spot it and how to keep it out of your palay.
What Is Basilicum polystachyon?
This weed belongs to the mint family, the same family as basil and oregano. It has no common English name, so most guides use its scientific name. In some areas, farmers call it pansi pansi. Basilicum polystachyon grows in rainfed lowland rice fields, where the soil dries out between rains and upland type weeds can move in.
As an annual, each plant grows, flowers and dies within one season. It spreads only by seed. Each flower spike can grow up to 10 centimeters long and holds many small flowers, and every flower can leave seeds behind. That is why one tall plant left to finish its cycle can seed a wide patch for the next crop. So the goal is simple: never let it flower in your field.
| Name | Basilicum polystachyon |
|---|---|
| Family | Lamiaceae |
| Weed group | Broadleaves (see the three groups) |
| Local names | Pansi pansi |
| Life cycle | Annual |
| Spreads by | Seeds |
| Where it grows | Rainfed lowland rice fields |
How to Identify Basilicum polystachyon
Squeeze the stem between your fingers. If it feels square, with four clear angles, you may have this weed. The plant stands upright, branches out and can reach about one meter tall. Its leaves grow in pairs, oval to long oval, with toothed edges. As a broadleaf weed, it has flat leaves with netted veins. At the branch tips, look for dense flower spikes up to 10 centimeters long, with lilac or pink flowers.
- Four angled, square stems that you can feel when you roll them between your fingers.
- Upright, branched plants that can grow up to one meter tall.
- Oval to long oval leaves with small teeth along the edges.
- Dense spikes of lilac or pink flowers, up to 10 centimeters long.
- Plants rising above young palay in rainfed patches that dry out between rains.
Why It Hurts Your Palay
Basilicum polystachyon competes with your palay for light, water and fertilizer. Since it can grow as tall as a meter and branches out, it can shade young rice and crowd the hills next to it. In rainfed fields, the risk climbs during dry spells. Without standing water to hold weeds back, upland type broadleaves like this one sprout and grow freely.
At harvest, its seeds can mix with the grain and travel to the next field with your seed. Dense stands also give insects, rats and other pests a place to hide. Because it lives only one season, the damage it does next year depends on how many plants you let seed this year.
How to Control Basilicum polystachyon
- Pull plants while they are still young and short, before the square stems toughen and the plant branches out.
- Remove every plant before the lilac or pink spikes set seed, and carry pulled plants out of the field.
- Where you can, hold water on the field through the wet months. A steady flood holds back upland weeds like this one.
What to Do at Each Age of Your Rice
- 0 to 5 days: keep the soil saturated. Use a pre emergence herbicide only if the field had many weeds last season.
- 6 to 10 days: hand weed in transplanted rice. In direct seeded rice, this is the window for an early post emergence spray.
- 11 to 20 days: keep water in the field, weed by hand or with a rotary weeder, and let Azolla and the Altica beetle help. Spray only if those fail.
- 21 to 30 days: top up the water and keep weeding. Spray only if weeding fails.
- 31 to 40 days (transplanted rice): hand weed. A spray this late is only a rescue.
- After any post emergence spray, bring the water back within 1 to 3 days at 3 to 5 cm and hold it for 4 to 5 days. Keep young rice above it.
Active Ingredients That Work on Broadleaves
If water and weeding cannot hold Basilicum polystachyon down, choose an active ingredient that works on broadleaves at the age of your rice. Each active ingredient in it is in a herbicide registered in the Philippines for rice. Shop by the ingredient on the label, never by the brand. If your field also has other kinds of weeds, the weed control helper in anee.io finds the ingredients that cover all of them.
| Rice age (days after planting) | Transplanted rice (lipat tanim) | Direct seeded rice (sabog tanim) |
|---|---|---|
| 0 to 5 days | Pretilachlor, Oxadiazon, Butachlor plus 2,4 D IBE, Pyrazosulfuron ethyl plus pretilachlor, Imazosulfuron, Penoxsulam plus butachlor, Tefuryltrione plus triafamone, Thiobencarb plus 2,4 D IBE | Pretilachlor, Oxadiazon, Pretilachlor plus butachlor, Butachlor plus 2,4 D IBE, Pendimethalin, Pyrazosulfuron ethyl plus pretilachlor, Butachlor with safener |
| 6 to 10 days | Butachlor plus propanil, Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Penoxsulam plus cyhalofop butyl, Pendimethalin, Cyhalofop butyl plus propanil, Imazosulfuron, Propyrisulfuron, Clomazone plus propanil, Thiobencarb plus propanil, Flucetosulfuron, Cyhalofop butyl plus florpyrauxifen benzyl | Butachlor plus propanil, Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Cyhalofop butyl plus propanil, Pyrazosulfuron ethyl plus pretilachlor, Pendimethalin, Propyrisulfuron, Clomazone plus propanil, Thiobencarb plus propanil, Pretilachlor plus pyribenzoxim, Penoxsulam, Flucetosulfuron, Cyhalofop butyl plus florpyrauxifen benzyl |
| 11 to 20 days | Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Metamifop plus bispyribac sodium, Bentazone, Cyhalofop butyl plus ethoxysulfuron, Propyrisulfuron, Fenoxaprop P ethyl plus ethoxysulfuron, Flucetosulfuron, Carfentrazone ethyl, Florpyrauxifen benzyl, Cyhalofop butyl plus florpyrauxifen benzyl | Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Metamifop plus bispyribac sodium, Bentazone, Pyribenzoxim, Cyhalofop butyl plus ethoxysulfuron, Propyrisulfuron, Fenoxaprop P ethyl plus ethoxysulfuron, Flucetosulfuron, Carfentrazone ethyl, Florpyrauxifen benzyl, Cyhalofop butyl plus florpyrauxifen benzyl |
| 21 to 30 days | 2,4 D amine, 2,4 D IBE, MCPA, Metamifop plus bispyribac sodium, Bentazone, Metsulfuron methyl plus chlorimuron ethyl, Fenoxaprop P ethyl plus ethoxysulfuron, Carfentrazone ethyl | 2,4 D amine, 2,4 D IBE, Cyhalofop butyl plus bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, MCPA, Metamifop plus bispyribac sodium, Bentazone, Metsulfuron methyl plus chlorimuron ethyl, Pyribenzoxim, Carfentrazone ethyl |
| 31 to 40 days | Metsulfuron methyl plus chlorimuron ethyl | Not listed for direct seeded rice |
Spray Safely
Use only herbicides registered with the Fertilizer and Pesticide Authority, and follow the label on the pack: the rate, the timing, the water and the protective clothing. Switch herbicide groups between seasons so the weeds do not learn to survive them. Our guide to herbicides for rice explains the groups.
Keep Basilicum polystachyon Out Next Season
- Plant clean, certified seed. Weed seeds mixed into the punla are the easiest way in.
- Keep the seedbed, the canals and the bunds free of weeds, so seed does not wash or blow into the paddy.
- Prepare the land well: flood, plow, let the weed seeds sprout, then kill them when you harrow. Level the field so water covers it evenly.
- Pull escapes before they flower and set seed, and carry them out of the paddy instead of leaving them on the bund.
- Keep the field clean after harvest and through the fallow, so fewer seeds build up in the soil for next season.
These steps work for every broadleaf weed in the paddy, not only this one. The weed management guide puts them in order for a whole season.
Not Sure It Is Basilicum polystachyon?
Take a clear photo of the leaf, the stem and the flower or seed head, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you which weed it most likely is, its group, and what to do at the age of your rice. You can also put the weeding days on your cropping calendar, so the team knows when to go in.
anee.io keeps your weeding, spraying and water on one calendar, and Anee answers when a plant looks wrong.
- Weeding days on the season calendar
- Photos and notes for every lot
- Anee, the smart farm technician, in Tagalog or English
Questions Farmers Ask About Basilicum polystachyon
What do farmers call Basilicum polystachyon?
How do I control this weed in my rice field?
Is this weed related to basil?
Get Basilicum polystachyon out of your field
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