Ok.

Let's also get rid of the run-on and add a short germination time:
Spores (Ex): Once a year, skullcap ivy produces hundreds of thistledown-like seeds. Should one of these seeds land on a suitable host (any warm-blooded sapient creature with hair), the creature must succeed at a DC 10 Fortitude save or the seed takes root and grows into a new skullcap ivy plant in 1d3 weeks. A skullcap ivy infestation can be removed by anything that kills the plant: the simplest method is rubbing the infested areas with strong alcohol before the plant germinates. However, some adventurers intentionally apply skullcap ivy spores and automatically fail their saves. The save DC is Constitution-based.