Huyton
just because you have a lot of owners in agreement with you, you don’t have a right to force the issue.
If as you say you have a majority of owners on board with you, write to the secretary requesting an EGM. You need to have at least 25% of owners to sign this letter/email in order to call an EGM. If you request a motion by yourself, it will be placed on the agenda of the next general meeting, which is likely to be the next AGM.
In your letter to the secretary, specify the exact wording of what you want eg trim x trees within 2 week so; have trees trimmed annually ; keep trees trimmed to x height/shape.
You will need to be specific as the committee may just follow the literal motion you put.
Remember that the committee represents the majority of owners. That’s how they got voted in. Make sure you do in fact have enough support from other owners, or you will just labelled a troublemaker, no matter that you may be right.