Alright, so it's my first time growing, and I have to both do it indoors due to weather, and grow it in an attractive jar so nobody gets grossed out. So I couldn't use a bag or a bin.

I chose to put the (oyster) spawn and substrate in a big, decorative colander since it has plenty of holes for air flow and whatnot. After about a week, some mushrooms are growing, but instead of growing at the top where they have room, they're trying to grow out of the holes on the sides of the colander.

Two of them are currently squeezing themselves out of a single hole, which isn't very big, and they've already maxed out the space they had for the stem. Is there any way I can get them to grow at the top instead? I have no problem with them growing out of the holes, but I assume they won't be able to come to fruition with the size of the hole limiting how large the stem can be at the connection.

You’ll find that most mushrooms that you can grow indoors will try grow out of any hole that is placed in the container that holds the spawn… even upside down. You can try to pick the fruits from the holes as they form, to try to encourage growth in areas where you actually want the mushroom to form.

You best bet is to use a container with significantly larger holes, if you must use a container with holes in it.