How to control cogon grass (Imperata cylindrica) with cover crops

Short answer: Mucuna bracteata is a cover crop commonly used to suppress cogon grass (Imperata cylindrica) in tropical plantations. Once it is well established, its vigorous growth and dense canopy shade out cogon. In a Malaysian oil palm trial, the cover crop treatments together cut weed dry weight by 97.3 to 99.9% and weed density by 94.77 to 99.73% compared with unweeded plots, 9 to 24 months after planting (Samedani et al. 2015); that was the general weed flora, not cogon alone. Cover crops suppress cogon by competition and shading rather than killing its rhizomes, so they are a long-term management tool rather than a replacement for herbicide or a means of eradication. On heavy infestations an initial spot-treatment is usually still needed to let the cover crop establish. Results vary with soil, rainfall, shade and cogon density.

Why cogon grass is a serious problem

Imperata cylindrica, known locally as cogon in the Philippines, is widely listed among the world's worst weeds. It spreads aggressively through rhizomes and wind-dispersed seed and colonises disturbed plantation soils quickly. Left unmanaged, cogon competes strongly with young palms and tree crops for water, light and nutrients, creates a fire hazard in the dry season, and adds significant recurring labour and herbicide cost for plantation managers.

Conventional management relies on repeated herbicide applications and manual slashing. Both are costly and labour-intensive, and both address the standing foliage rather than the rhizome bank, so the relief is temporary. Cover crops add a biological, longer-term layer of suppression by occupying the ground and cutting off the light cogon needs, and they are best used alongside rather than instead of conventional control.

Please read: cover crops suppress cogon through competition and shading. They do not kill cogon rhizomes and should not be treated as a herbicide substitute or as a means of eradication. Nothing on this page is a guarantee of a particular level of control. Where a herbicide is used, follow the product label and the pesticide regulations that apply in your country.

White, silky flower heads of cogon grass (Imperata cylindrica) — Cogon grass (Imperata cylindrica) in flower.

Cover crop effectiveness against cogon

Cover crop	Relative suppression (field experience)	Establishment method and rate	Time to cover (published record)	How it suppresses cogon
Mucuna bracteata (MB)	Strong	Drilled or in holes, 1 kg/ha sown alone, or nursery seedlings (about 320 seedlings/ha from about 500 seeds, 75 g, on deep peat, MPOB TT No. 501; 680 seedlings/ha on mineral soil, Samedani et al. 2015); not broadcast	About 100% ground cover at 6 months at 680 seedlings/ha on mineral soil (Samedani et al. 2015); 78% at 24 months at 320 seedlings/ha on deep peat (MPOB TT No. 501)	Dense smothering canopy, strong light exclusion
Pueraria javanica (PJ)	Good	Drilled or in holes, 10 kg/ha sown alone	Site-dependent; no published figure we can cite	Dense ground cover, light exclusion
Calopogonium mucunoides (CM)	Moderate	Drilled or in holes, 10 kg/ha sown alone	Covers the soil 3 to 6 months after sowing (PROSEA 11)	Fast initial cover, less persistent over time
Calopogonium caeruleum (CC)	Good	Drilled or in holes, 5 kg/ha sown alone	Slow: about 20 months to full cover (PROSEA 4)	Stoloniferous spreading, better shade tolerance

Ratings are a qualitative summary of plantation field experience, not measured trial results. Seeding rates are our recommendation, each for one species sown alone; for a mixture, the quantity of each species is set on the quotation for your site. Drill or plant in holes: broadcasting does not guarantee good germination, especially where the soil dries out easily. Seedling densities and timings are the published figures named, under the conditions in each source; your site will differ.

Recommended approach: MB plus PJ combination

For heavy cogon infestations, a two-phase approach is recommended.

Phase 1 (knockdown and MB planting): spot-treat active cogon patches, following the herbicide label and local regulations, and allow the die-back period the label gives. Then plant Mucuna bracteata into the treated areas, drilled or in holes at 1 kg/ha sown alone, or as nursery-raised seedlings transplanted from polybags. This gives MB a head start before cogon regrows.

MB is not broadcast. Recommended seeding rate: 1 kg/ha sown alone, drilled or planted in holes. Mucuna bracteata can also be raised in a nursery and transplanted: MPOB TT No. 501 used about 320 seedlings per hectare on deep peat, two per palm point, raised from about 500 seeds (75 g), and Samedani et al. (2015) used 680 seedlings per hectare on mineral soil.

Phase 2 (once MB is running): once MB is established and actively running, drill Pueraria javanica seed or plant it in holes in the inter-rows and in areas MB has not yet reached (recommended seeding rate 10 kg/ha sown alone; the quantity for your block is set on the quotation). PJ fills the gaps and carries longer-term cover as the crop canopy closes and MB naturally thins.

Where establishment goes well, the combined MB and PJ cover can reduce cogon to a minor component of the ground flora. The cover then helps limit re-establishment from rhizome fragments and windblown seed, but it does not remove the rhizome bank, so keep monitoring gaps and disturbed ground and expect to spot-treat occasional regrowth. Outcomes differ between sites, and you should verify the approach against your own field conditions before scaling it up.

Frequently asked questions

How long does it take for cover crops to suppress cogon?

There is no published timing for cogon specifically. For Mucuna bracteata, published records range from about 100% ground cover at 6 months (680 seedlings/ha on mineral soil, Samedani et al. 2015) to 78% at 24 months (320 seedlings/ha on deep peat, MPOB TT No. 501), and in the Samedani trial weed dry weight under the cover crop treatments was 97.3 to 99.9% lower than in unweeded plots 9 to 24 months after planting. The pace on your site depends on cogon density, rainfall, soil fertility and how much light reaches the ground. Cogon rhizomes can persist in the soil under a closed cover for several seasons, so plan for ongoing suppression rather than a one-off clearance.

Can cover crops alone control cogon without herbicide?

Cover crops alone can suppress cogon, but establishment is slower and less reliable without an initial knockdown. On light infestations, planting Mucuna bracteata directly can work. On heavy infestations an initial herbicide spot-treatment generally gives the cover crop a much better chance of closing over before cogon regrows. Cover crops are not equivalent to a herbicide programme and should be planned as part of an integrated weed management approach.

Will cogon come back after cover crops are established?

Cogon can return. A dense, healthy cover crop stand blocks much of the light that cogon needs to regenerate from rhizome buds, which keeps it in check, but the rhizomes are not killed. If the stand is thinned or damaged by fire, heavy pruning, grazing or drought, cogon commonly re-establishes in the gaps. Maintaining cover crop health and closing gaps promptly is the main defence.

What about using cover crops with coconut trees?

Cover crops work well under coconut. The wider spacing of coconut plantings (commonly 8 to 9 m triangular) leaves more inter-row space and light for a cover crop. Pueraria javanica is often a good fit under coconut because of its moderate shade tolerance.

Tell us your block size, crop and cogon pressure and we will recommend a seed mix and quantity. We reply within one business day (Philippine time).

Get a Custom Weed Management Quote

Recommended seed: Mucuna bracteata (MB) and Pueraria javanica (PJ).