A few months ago I got a magnolia jane tree and planted it. Yesterday I was looking a little closer and I realized it wasn't just a magnolia in the pot, there was a tag along as well. But I cant figure out what it is, the closest ive gotten is eastern cotton wood, but im not entirely sure. What do you think? (new hampshire)

I am not entirely sure what it is. Maybe a poplar seedling, specifically a cottonwood.

You both agree and are correct: that is an Eastern Cottonwood seedling - Populus deltoides.

It will need its own growing environment, if you choose to keep it. It will eat your Magnolia...

They have deep, strong tap roots, and I have found them valuable for erosion control.

Where is the magnolia? Was it ever there?

Just my experience, cottonwoods are dirty weak trees.
They can break in ice storms , drop limbs in the wind & make messy "cotton" that can pile up like snow.
They like water so they are prolly useful stabilizing stream banks, etc but they are not IMO, choice trees.

We had discussed planting some popples for quick shade knowing we would cut them down once the nicer trees got some legs under them but never did.
Some folks are pretty allergic to the cotton.

I'm no expert - just my experience.

Cottonwoods....the females are a mess. The white seeds clog air conditioners and your car vents. The males do not put out the seeds. The problem is that you will not know if you have a male or female tree. It can take 8 or up to 12 years to know if it is male or female. Then you are already dealing with a tree over 25 ft tall.

Male or female, both put out extensive root systems that are problematic to your foundation, water, sewer or septic. On a mature tree roots can go an easy 100 feet or more.

The males are good for erosion. A good tree for drying up the ground in low areas that have standing water. I have found the wood chips made from cottonwood to be most beneficial. They hold can hold quite a bit of water. The wood chips do discolor quickly to a grey color.

Your tree... your decision. I rip them out...the weekly clogging of the air conditioner from the neighbors tree was a pain.

May October be a wonderful month full of surprises!