Have you tried all of the auxillary agents available in the Agents Collective? Even though they're not specifically grass, tubas, or bramboo, they are still seeds, food and fruit. One or more of them might be useful.
Have you ever learned a second language? Learning to code is like learning how to speak grammatically and logically in another language to the agents to tell them how they should behave. The best thing to read as far as coding goes is the - think of it as being like a dictionary of all the codes that are used in the game. You might also like to explore the tutorials linked from or to help you get started.
A couple of other agents that you might be interested in to help 'fill the gap' are the by Moe and the by Chani.