That's my biggest problem.

There are two ways to handle them:
1.) The polygons within a model are sorted by their internal number (time of creation). So the first created polygon will be rendered first. For my flower model (see screenshot) I first modelled the lower part of the flower. So this lower part will always be rendered in the background. And the white flower was created last, so it is always rendered in the foreground. So I have no sorting problem.

2.) The model itself is sorted by it's X,Y,Z-Position. You can change the centre of the model to affect the rendering/sorting.

It is much work to prevent wrong sorting.

So the performance problem is still there afterwards and your grass looks ugly with it? If so, your problem is not alpha blending, but something else.

Can you send me the project to timo (dot) stark (at) dev-software (dot) com?
I can give it a check this evening.

Greetings,
Timo

I have seen that you use bones animation for your grass models?! Can this be the problem (bad coding of animation)?

3run, what frame rate do you get when you run your project in window mode?

Yes, there are bones, but I don't use them (model isn't animated BTW).
I've converted example from AUM, where grass where reacting for player and moving randomly by faked wind.

Slin@ grass is highlighted (as well as trees), and yes, still from time to time I get low framerate.

Pappenheimer@ it's same jerking from 59-60, when I get in grass sometimes I get this 20-40 fps.

TechMuc@ thank you for offering your help, we'll see may be tomorrow I'll send it to you.