Cat and Lucky Bamboo reaction time?

I was unaware that Lucky Bamboo was poisonous to cats and found my cat chewing on it this morning. I don't think he swallowed any, but I still removed the plant from the house immediately and called the vet who said he should be fine as long as it was ingested. My question is how long would it take to figure out if he is okay? It's been about an hour and he seems totally fine, but I didn't know if I could expect a bad reaction immediately or quite a bit of time. Help please!