Basal stem rot (BSR) caused by Ganoderma boninense remains the most destructive disease in oil palm monoculture plantations. This study investigates the nature of Ganoderma infection and survival under mixed planting with rhizomatous plants and its impact on the growth of oil palm. Two mixed plants (oil palm seedling and Java turmeric, galangal, or ginger) and single planting of those plants were inoculated with Ganoderma boninense-colonised rubber wood block (RWB). The results showed that Ganoderma inoculation in mixed planting caused an infection on both host species (dual-host infection). Under mixed planting for 9 months with Java turmeric and ginger, the disease index of oil palm was reduced by 47%-59% compared to the single planting. Planting oil palm with rhizomatous plants showed a minor effect on the decay of RWB and fungal survival but planting with ginger induced basidiocarp formation. The rhizomatous plants habitually did not exhibit allelopathic inhibition of oil palm growth. Growth of Ganoderma-infected seedlings was recovered under mixed planting. This study highlights a novel insight that mixed planting with rhizomatous plants can interfere with and reduce Ganoderma disease in oil palm.