Additional Ideas (6)
A giant variety of common nettle, it has arrow-head shaped leaves, greyish varagated foliage and is covered in razor sharp, poisonous spines. The poison causes severe pain as well as violent muscle spasams which could cause a victim to fall, possibily into more nettle. Since large doses will disrupt breathing, falling into the patch is not a good outcome.
The toxin (which is a neurotoxin) biodegrades rapidly and will not keep well if harvested from the plant.
A brightly colored flower with tall spires similar to foxglove. The Rapacious version is both very much larger then normal snapdragons, and far more active. The spires are very tall - 12-14' in height, and the spires are studded by very large flowers, each about 1 foot across. The flowers appear in many brilliant colors, but hide a secret. They are equipped with fang-like thorns that will be used to bite anyone coming close to the plant. A victim will be subject to 2-4 bite attacks at a time but an individual plant can only attack one target at a time.
The plant is non-toxic, but the razor-sharp thorns can cause serious damage.
Miremoss appears as a fine green carpet and is otherwise not very different from other common mosses. What makes it dangerous is that it is very very tough, and exudes a very strong adhesive if damaged. This adhesive has a short setting period - usually 1-2 minutes after contact with the moss. When it sets, it does so suddenly and will hold fast most materials with a bond strength of magical intensity. Since the moss can occur in large patches, a victim could be stuck on the moss. Removing footware is a good solution if the victim is no longer on the moss or can fly, but if they are still on the moss, they will still have a serious problem.
The moss is quite tough and requires signficant hacking to cut through. Generally it will take longer to cut a significant patch then it will take for the adhesive to cure, possibly sticking weapons to the ground.
The adhesive is soluble in alcohol. It could be harvested, but since it begins curing on exposure to air that would be a difficult process.
"I'm not a boozehound, I just want to be prepared!"
Locals aware of the plant's properties might wear large planks of wood on their feet, similar to snowshoes, to spread their weight evenly enough to avoid damaging the plants. Alternatively, they might coat their shoes heavily with beeswax, to keep them from adhering.
I could see people cultivating this plant for its useful adhesive properties.
This bush is generally low key and resembles an oversized (4' height) common Euphorbia (Light green foliage, many small leaves, spherical overall shape). It is, however, somewhat intelligent and of a rather dour disposition. It has a caustic, milky sap that it can project up to 20'. This sap is very caustic and will inflict serious burns to organic materials. It is easily upset by sudden movement, sound, or light and will spurt sap until whatever disturbs it is gone, or it depletes its supply (usually 10-12 discharges per day).
If somehow subdued, it could be harvested for its sap that can then be used as-is as a weapon, or for use in alchemical work.
Singeweed appears very similar to Red Hot Pokers (http://www.freefoto.com/preview.jsp?id=12-65-53&k=Red+Hot+Poker") but differs in two major ways.
It is animated, capable of movement, and it is infused with elemental fire. When disturbed by intruders, it will envelop its flowers with flame and attempt to strike intruders in range. Strangely, the flames do not hurt the flower itself. Though capable of movement, they will not move further then 10' from their original rooting site.
The elemental energy is tied to the plant's life force, so if ripped up or otherwise killed, the energy will dissipate. Magic which works with elemental fire will apply to the plant.
This grass appears as normal, overgrown grass - standing about 18" high with the occasional even taller spire covered with seeds. Some of these spires are different, containing a very strong, stiff core and ending in a barbed thorn. The thorn is quite toxic and sharp enough to easily pierce leather or find it's way through chain links. The spire is also capable of moving and will slash or stab at anything warm which comes within 18" of the plant.