You could "try" to stop them...

They grasped and stroked my ass and slowly started to pressure against my asshole. I groaned in mild frustration and tried to reach down with my arms to pull them away, but the plant held me firm. I could use all of my strength to rip away, but... They continued to massage my sphincter; I felt some sort of ooze slicking my clenched entrance. "Oh fuck it, if they care enough to lube me up, then they are more considerate than-"

A sudden burning sensation took hold as one of the tendrils slithered inside my ass, formally taking my anal virginity.

"ffuuUCK," I shuddered. The brand-new feeling was accompanied by a strange tingle that seemed to travel throughout my entire body. It was only about the diameter of a feather quill's shaft, but it felt like it was pushing into my deepest parts.

I could feel it sliding up my rectum, testing my walls for resistance. I winced as it pushed, but I couldn't really tell if it was hurting me or not; the feeling was entirely unique to me, so I had no idea what it was 'supposed' to feel like. Suddenly, it reached a curve inside me that I didn't even know I had; it pressed, causing a brief cramp of pain, then it made it past the barrier into my colon.

I weakly cried out in soft pain as the plant devoted more tendrils to my ass. Now it felt a couple of fingers large, still manageable, but becoming more invasive. The little vines also increased their speed, their gentle nature fading with each moment. I could feel pressure growing against the sides of my rectum as all of the coils moved in and out of me.

"Oh holy... hol- HOLY FUCK!" I cried out in surprise as the rest of the tiny vines of the plant pushed past the bend. I could feel the plant moving in and out, its tendrils digging into my insides as they pumped. Their urgency was a clear sign of what was to come, but I still didn't expect it.

I felt every one of the coils rapidly thicken as they continued to pump. But then, they spasmed in unison, spurting their load of sticky liquid into my colon. As they continued to pulse and thrust, their 'cum' just kept cumming, until I felt completely full.

Still, the plant continued, its tendrils moving faster and faster. A slight stretch of my stomach gave me pause, but I could deal with that. I didn't know what exactly it was, but it was hot, warming me from within. I wondered why the plant hadn't used any of the other holes.

Finally, I felt the plant slowing down. "Gooodneess..." I moaned as the last tendril slowly stopped pulsing.