First Time Gardener: Question about blueberry bush container

Hello everyone,

This is my first garden so I am struggling with absorbing the tons of information out there on successfully growing fruits and veggies. I researched this one, but couldn't confirm my hunch.

I have heavy clay soil and literally no top soil (we think it was sold off when the house was built in 1977). So, all of my seedlings are in containers in my backyard.

I planted my two blueberry bushes in a 65 gallon black fabric pot container that I filled with a combination of 50/50 soil/compost that I purchased from a local vendor, plus additional bagged compost, Espoma Soil Acidifier, peat moss and bagged pine bark mulch. After I planted the two blueberry seedlings, I added a top layer of store bought bagged compost. Finally, to protect from frost and weeds, I covered the container with a row cover.

I planted the blueberry seedlings on 3/14/15.

Today, 4/3/15, I noticed what appear to be wild onions growing in the container. I am starting to see some buds form on the blueberry bushes as well. At first, I thought maybe it was the blueberry bush sending out shoots, but it made no sense. I dug down into the soil to get to the source of the "onion" and to my great surprise, it went down very deep, like 10". As I dug, I found more "onions" working their way to the surface. When I got to the bottom of the sprout, it was self contained in capsule so I knew it could not be part of the blueberry plant.

While I was digging I also came across spots of a yellow powder-looking material in the soil. I did not see anything that looked like mushroom growth though.

My questions are (1) Are these wild onions and should I dig down to the root to remove them? (2) Is the yellow powder sulfur because of the acidifier I added? And, is that a good sign or a problem for the blueberry bush?

Here is a picture of the onion.

They don't appear to be onions, which grow from a distict bulb. These appear to be growing from seeds, and look like some sort of grass (i.e. grain, cereal) that sounds as though it must have been in the soil.

Thanks Alta! I didn't think about it being a grass-type growth. Do you know if that is common in store bought soil or compost?

If the compost has not been sterilized, or composted then seeds are a possibility. Read the ingredients. If it has any kind of animal manure then there may be spilled foods (grains) mixed in. Not much, and not often.

Thanks Diana!

Do you know if the yellow powder-looking material in the soil is normal?

Could it be pollen that has fallen from nearby trees? Your soil for blueberries is excellent. All seems in your favor. Here is one lesson you need to get engraved in your head: weeds are EVERYWHERE and removing early, esp. in containers is your best defense. You could have Gucci dirt and some bird or the wind are going to drop seeds, weeds seeds for the most part.

Yellow powder looking stuff on the surface could be pollen blown in from nearby. Often pine or related trees, but most plants have yellow pollen, could be almost any.
Yellow powder looking stuff deep in the soil is more likely fungus. Not a big deal. Fungi grow on things that were once living, such as composting leaves, twigs, sawdust and so on. They are helping to decompose the organic matter and make it a better soil.

The yellow powder looking stuff is definitely deep down. I found it while digging up the "onion" things I was trying to identify. I'll take a picture and post.