The BAB is listed correctly as +2, and Str should give another +2, so tendril +4. Probably this is copy-paste from the hydra.
Ohh! I just noticed that the grapple is +8. Maybe we copied that over to the attack roll by mistake.
I'm happy to go with your changes. Is the grapple ok?
Feats: Weapon Focus (tendril), Power Attack?
They seem OK to me.
Removing the severed vine does 1d4+Con bonus damage? Con based DC for the Heal check?
So do you want to do Con damage instead of hp damage when the vine is removed?
CR 3? Treasure: 1/10 coins, 1/10 goods, 1/2 items? Advancement: - like the hydra? The plant's base is 5 ft long?
That all sounds fairly logical. Are we going to make the plants with more tendril's larger or keep them all the same size?
Ready to move to the 4-tendril version?
I think we have missed this out:
The plant retreats from flame, and any stem that is seared releases its victim and curls back up around the base.
Maybe that needs to go into the combat section as flavor. Or maybe this plant should have some sort of vulnerability to fire.
The "curls back up" refernce suggests to me that the tendrils may naturally sit curled up around the base of the plant.
I also think we need to explain a bit about the combat tactics of the plant in the combat section (before the mention of cutting of tendrils).
The plant normally lies dormant and immobile with its thorns lynig flat against its vines. So I'd say a spot check against DC X will reveal that the plant has dangerous spikes, otherwise people should see it as a normal plant. (A search check should provoke an attack.)
It waits until a creature comes into range and then lashes out. I'm not sure how it came to get "low light vision". I think that might be a cut and paste error. I think it should have something like tremorsense or some sort of bodyheat detection.
Several plants are said to sometimes attack at the same time, but I'd make that a co-incidence. Someone fighting a bloodthorn should set of nearby plants by their movement.