I am trying to create a grassy field following a BlenderGuru Tutorial: https://www.youtube.com/watch?v=zhYtJ_VmvXE. However, when I add the hair emitter onto my field to create the grass, instead of pointing upwards the grass particles point in random directions and I'm not sure why. Here is how it looks:
There could be many causes for this problem, from my experience:
Your Particle system has an incorrect initial orientation, although this is less likely, be sure to check which one fits best.
Your particle system would probably be using children if you're generating a meadow of grass, as there's a lot of grass. These settings affect the children greatly, and can lead to some very strange things happening, if used incorrectly.
More specifically to your case, it's likely a clumping error.
In such cases, clumping can cause them to bend very strangely, generally toward, or away from the clump.
It could also be a problem with your Particle system's velocity. The Emitter Object settings especially, can cause some pretty outlandish results when used extremely, as they affect the direction and shape of your particles, as well as their origin points, especially in the case of children.
I'm sure that Andrew stresses quite a bit over applying scale, rotation, and location to your models, this is very important. It's also important to check that all of your grass models are properly lined up, all facing the right direction. Although, in your image, you seem to have Scale, Rotation, and Global disabled, so that is less likely to be a problem than their absence.