Family: Urticaceae
Pilea hyalina is a small herb and a major weed of containerized plants posing a significant threat. It is a member of the Nettle family, Urticaceae, and lacks stinging hairs. First detected by HDOA staff at a nursery in Kea’au, it is thought to have arrived in a contaminated pot from Costa Rica. As of 2024, it has only been detected on Hawaii islands, but its presence is widespread within the nursery industry. While it typically doesn’t thrive outside a potted plant, it has been observed forming dense thickets under growing tables and near artificial ponds. The threat is not confined to Hawaii, as invasions outside its native range have also occurred in Belgium and, more recently, South Indian states (Karnataka, Kerala, Maharashtra, and Tamil Nadu).
P. hyalina is native to the American tropics, from Mexico and the Lesser Antilles to Chile, Argentina, and Brazil. In Guatemala, it is a weed of coffee plantations. The shade-tolerant plant thrives in shallow substrates, like another weedy relative, Pilea microphylla. It is unknown how many seeds P. hyalina produces; based on observations, it can be extensive. The tiny achenes are difficult to see and can easily be accidentally introduced, underscoring the need for careful plant management.
Prevent: Quarantine new plants before introducing them to a nursery bench. It’s essential to ensure that plants are free of contaminants. Mulching potted plants or using something like a Mulch Ring Tree Protector Mat will help to slow the spread of all weeds of containerized plants.
Description and Dispersal:
- Erect herb
- Quadrangular stem
- Inconspicuous stipules
- Bluntly serrate, oppositely arranged leaves
- 2 to 4 Inflorescences per node
