Triffid

The huge flower turned towards them. Around its base, wooden, claw-like roots rattled against its bulb.

"It's telling the others we're here." Old Tom said to his granddaughter. "It uses infra-sound, like a Lion, or an Elephant to communicate. The flower acts like a trumpet. They're very co-operative you know. They share their kills." He looked at her through his helmet. "Your helmet on properly?"

"Yes granddad. And my collar is zipped up too." In front of them, the seven-foot plant started hissing like a boiling kettle.

"It's going to strike. Be brave now little one."