I went looking to see what I could find on the Giant Sundew. Where I thought I saw it turns out to be the cover of Expedition to the Barrier Peaks, which is not a Sundew. I did find it in the Monstrous Manual 2nd Ed and another online.
The sundew in the Monster Manual has some good ideas. It just needs some updating. Oddly both entries give it a movement speed, slow but it can move. Figured I would share the info.

Monstrous Manual 2nd Ed:
The sundew detects moving creatures by vibrations. When anything moves within 5 feet of it, it lashes out with its tendrils. Its body is covered with hundreds of tendrils, and a maximum of six can attack each creature in range, each round. The tendrils exude sticky globs of sap. For every three tendrils that attach to a victim, the victim suffers a — 1 penalty to attack rolls. The sap contains a mild enzyme that inflicts 1 point of damage per round for each tendril striking the victim, regardless of whether or not the tendril is still attached, A successful open doors roll breaks a tendril; each tendril must be checked separately, up to once per tendril per round. If a sundew's attack roll is an unmodified 20, it has struck the victim's mouth and nose, clogging them with sap; suffocation occurs in ld3 +1 rounds unless the sap is removed. The sap may be dissolved by vinegar or alcohol.


The one found online is here. It seems to be more of a physical attacker than I imagined. The Stupefaction Pollen attack and the adhesive dissolving after it dies seem a bit odd but not beyond reason
https://www.d20pfsrd.com/bestiary/mo.../sundew-giant/

What the website GrowSundews.com has written gives one a lot of ideas.
The leaves of sundews are covered with "tentacles". The tip of every tentacle contains a nectar gland, which produces a globule of a sticky digestive enzyme. When an insect lands on the leaf, they get stuck on the dew. As they struggle to get out of the dew, the tentacles/leaf start(s) to wrap around the insect (through a complicated biological process involving several action potentials). The dew eventually suffocates the insect, and it stops moving.

Reading about sundews the older Monster Manual has the right idea. A grappler, suffocating, acid-attacking creature, the more you struggle and don't get away the more you are attacked. The chance to suffocate is too good an idea. One of the few simple deaths that strikes fear into the hearts of players.