After talking to the man inside the house to start the mission, simply head outside and gather the beehive plants in the yard. Return them to the man then head outside again and gather x3 Heliconia plants. Head to the hill to the north and gather the key Heliconias there.
Deliver it again to the man and he'll send you off to gather Screw Pines this time. Head to the location and gather the plants again. Finally hand them over to Alfie to get your reward and to unlock the Nature Boy recipe.
Not a glitch you have to stay in the area that looks like shallow water on you map and find the plants only in that area.
I had a similar problem. I collected the beehive plants and was able to interact. But after collecting 3 Heliconias I was not able to interact. I have no idea why - I didn't interrupt the collecting, didnt' fill the rucksack. The only thing I can think of is that I get double the number of leaves when gathering (one of the skills). I'll try leaving the area and starting over to see what happens.
I did the same thing and encountered the same problem.
There is a bug in this task. I collected the Beehive and returned them. On my way to find Helaconias, I stumbled upon a bear and killed and skinned it. After that, I could collect tons of Helaconia without them being registered. I had to leave the area and restart the task. So I think you have to stick to the plant gathering during this "mission" or the game loses track...