Panicum maximum aka Guinea Grass

Panicum maximum is a large, densely tufted perennial grass that exhibits considerable size variation depending on the variety. Tall/Medium (TM) types, commonly called Guinea grass, reach 1.5-3.5 metres in height with stem diameters of about 10mm. Short (S) types, often called Panic grasses, grow 0.5-1.5 metres tall with narrower stems around 5mm diameter. The plant forms dense clumps from short creeping rhizomes, with individual leaf blades reaching up to 90cm long and 3.5cm wide. Growth rate is fast, particularly during warm, wet seasons.

Panicum maximum is native to tropical and subtropical Africa, with a distribution spanning from Senegal in West Africa eastward to Ethiopia and Somalia, and south to South Africa. It also occurs naturally in the Arabian Peninsula (Yemen) and the western Indian Ocean islands including Madagascar and Mauritius. The centre of genetic diversity is in Tanzania and Kenya. In its native habitat, it grows in open grasslands, typically under or near trees and shrubs, along riverbanks, and in Mixed and Sour Bushveld vegetation.

Panicum maximum thrives in tropical and subtropical climates with average temperatures of 19-23°C. The plant is frost-sensitive—when dormant, it can survive temperatures down to approximately -2°C, but young growth sustains damage at 0°C. Some cold-hardy varieties like 'PUK P8' can withstand temperatures as low as -13°C. The grass grows best during warm, wet seasons and may go dormant or show reduced growth during cooler periods. It is suitable for USDA zones 10-12.

Panicum maximum naturally grows in tropical regions with high humidity and rainfall above 1,000mm annually. It thrives in humid environments and is often found in shaded, damp areas under trees and along riverbanks. However, the species is adaptable and can tolerate drier conditions once established. Shorter (S-type) varieties are more drought-tolerant, requiring only 800-1,100mm annual rainfall, while taller varieties prefer 1,100-2,500mm. The plant generally struggles if dry conditions persist beyond 4-5 months.

Panicum maximum can be propagated by seed or vegetatively through rooted tillers and stem cuttings. For seed propagation, sow in spring to early summer in fertile, well-prepared soil, pressing seeds to no more than 1cm depth. Note that some varieties have seed dormancy requiring up to 18 months after harvest for maximum germination. Rolling after sowing improves germination rates. For vegetative propagation, plant rooted tillers or cuttings in rows 1.25-1.5m apart, with 0.5-0.6m spacing within rows. The plant reproduces both sexually and through apomixis (asexual seed production), meaning local populations tend to be genetically uniform.

Panicum maximum is exclusively an outdoor grass, naturally found in tropical and subtropical regions. It grows successfully outdoors in USDA zones 10-12 and UK hardiness zone 10. The plant requires warm conditions and is frost-sensitive, though dormant plants can survive brief exposures to -2°C. In suitable climates, it can be grown in open pastures, under trees, or along water features.

Yes, Panicum maximum produces distinctive large, open panicle inflorescences that can reach 60cm in height and 20cm in width. The lower branches of the panicle are arranged in whorls of 3-7 branchlets, giving a characteristic appearance. Individual plants can produce up to 9,000 seeds. Flowering patterns vary significantly by cultivar—some flower in a single flush, others have multiple flowering periods throughout the growing season, and some are indeterminate. Some cultivars are short-day plants while others are daylength insensitive.

Panicum maximum is wind-pollinated, which is typical for grasses in the Poaceae family. The plant is self-fertile, meaning a single plant can produce viable seed. Additionally, many varieties reproduce through apomixis—a form of asexual reproduction where seeds are produced without fertilisation, effectively cloning the parent plant. This is why local populations of Guinea grass tend to be genetically uniform. Apomictic reproduction is especially common in polyploid (tetraploid) varieties.

The primary pest concern for Panicum maximum is spittlebug, with several species (Notozulia entreriana, Deois, Mahanarva, and Aeneolamia species) causing significant damage. Susceptible cultivars include 'Colonião', 'Tobiatã', 'Vencedor', and 'Gatton'. Disease issues include ergot (Claviceps species), leaf spot (Cercospora fusimaculosus), and various fungal pathogens including Fusarium roseum and Tilletia species. Smut and bunt can affect seed production in certain regions. Some cultivars like 'BRS Zuri' and 'Mombaça' have been bred for improved spittlebug resistance.

Panicum maximum varieties are broadly categorised into two types. Tall/Medium (TM) types include: 'Colonião' (2-3m, drought tolerant), 'Mombaça' (1.65m, high spittlebug resistance), 'Tanzânia-1' (1-2m, 80% higher leaf production than common Guinea grass), 'Tobiatã' (over 2m with broad leaves), 'Vencedor' (1.6m, acid soil tolerant), and 'BRS Zuri' (tall, disease resistant). Short (S) types include: 'Gatton' (1.5m, high yields), 'Petrie' (1-1.8m, excellent shade tolerance, marketed as 'green panic'), and 'Sabi' (1.5m, more waterlogging tolerant). Each variety has distinct characteristics suited to different growing conditions and management systems.

Proper defoliation management is crucial for Panicum maximum persistence. For tall/medium (TM) varieties, avoid cutting or grazing below 30cm height, with an optimal cutting interval of about 4 weeks. Shorter (S) varieties can tolerate lower grazing but benefit from rotational systems. The plant is susceptible to frequent heavy defoliation, which can weaken stands over time. When grown for cut-and-carry or hay, harvesting at 4-6 week intervals maintains productivity. The grass regenerates readily from rhizomes after cutting or even fire.

Beyond its primary use as a major tropical forage and pasture grass, Panicum maximum has several other applications. The plant has potential for biofuel production, as it can be grown to produce biomass for making alcohol. The straw is traditionally used for thatching roofs, and the culms (stems) can be used for making brooms and baskets. In traditional medicine, it is used to treat heartburn and tympanitis, with the plant considered diuretic and laxative. Fresh plant sap can be applied to wounds as a healing agent. The grass also provides ecological benefits as food for seed-eating birds and habitat for butterfly larvae.

Panicum maximum has limited traditional medicinal applications. The plant has been used to treat heartburn and tympanitis (abdominal bloating). It is considered to have diuretic, laxative, and preventive properties. Fresh plant sap can be applied externally to wounds as a cicatrisant (wound-healing agent). Bundles of the grass have been traditionally applied to the head for headache relief. However, medicinal use is minor compared to its agricultural importance, and PFAF rates its medicinal value as 2 out of 5.

Guinea Grass should be watered regularly, allowing the soil to dry out between waterings.

Guinea Grass loves a well-draining soil. Perlite and vermiculite help with drainage, while coco coir adds organic matter, so a good potting soil mix will have all three. You can improve store-bought soil by adding some perlite to it.

Guinea Grass requires abundant, bright, and direct light to thrive. The best placement for this plant is within one foot of a window to ensure it receives enough light. If you live in an area with more extreme weather, such as hot summers or cold winters, you may need to adjust the placement of the plant accordingly. During hot summer months, it is important to place the plant away from full sun, as this can cause the leaves to yellow or burn. During cold winter months, it is best to move the plant closer to the window to take advantage of the extra light that can help it survive. By keeping an eye on the current weather in your area, you can make sure your Green Panic Grass is always in the right place to thrive.

The Guinea Grass should be repotted when it has doubled in size or annually, whichever comes first. Providing fresh potting soil with all the essential nutrients each year ensures the plant's well-being, eliminating the need for fertilizer. Remember, plants derive their energy from the sun and not fertilizer.

Ploi lacks confirmed information on the toxicity of this plant. If you, a relative, or your pet accidentally consume plant material with unknown toxicity, it's best to consult a medical expert.