How to make the top of a growable plant type a different texture

So I am making a new type of Kelp for my custom dimension, and there seems to be a slight issue. The Kelp in vanilla Minecraft has a different texture for the top part of the plant. It's a lot shorter as compared to the rest of the plant. And when making a custom plant in MCreator, the Growable Plant type only has one texture available to use. Is there any way to make it the same way it's in Vanilla? With the top part having a different texture?