Grub Fern (Polypodium formosanum): Creeping Epiphyte with Caterpillar-Like Rhizomes

Overview

Grub fern (Polypodium formosanum), also called caterpillar fern, is an epiphytic fern native to Taiwan and the Philippines. Its creeping rhizomes are thick, fleshy, and densely covered in soft, golden-brown scales—resembling plump caterpillars or grubs crawling over branches and rocks. From these rise simple, leathery, glossy green fronds (6–12 inches) with wavy margins, creating a lush, textural carpet.

Unique Appeal

• Characterful Rhizomes: The "grubs" are a delightful oddity.
• Epiphytic Versatility: Mount on wood, cork, or grow in hanging baskets.
• Durable Fronds: Leathery, long-lasting foliage.

Culture

Bright, indirect light. Loose, well-draining epiphytic mix (bark, moss, perlite). Keep evenly moist; high humidity. Warm temperatures; minimum 50°F (10°C). USDA zones 10–11 outdoors; excellent mounted specimen or terrarium plant.

Taxonomic Profile

With its whimsical "caterpillar" rhizomes and glossy fronds, grub fern adds personality to any epiphyte collection.