Could you post a picture? if we can identify the trees we may be able to make this easier on you, You may have to remove the shrubs as well if the trees are anything like oaks or maples. if it something like pin cherry or dogwood those have more shallow root systems.

I think one of the little trees might be a Ash tree

I can't remove the spirea. The landlord doesn't permit altering the landscaping but tenants are allowed to grow things if they're in pots. The gardener just keeps trimming the trees so they are level with the spirea but they always grow taller again.

If I had known they were there, I would have pulled them sooner but I didn't notice them until they were tall enough that they were visible among the spirea. They seems to be growing close to the roots of the spirea too so they may have their roots tangled with them. If the mini trees are cut the part in the ground would just grown tall again but I wanted to keep the tree and just remove it from the bushes. There's a lot of trees at the edge of the woods that have winged seed pods flying through the air in Autumn so I think one or both of the mini trees must be that kind.

I will have to wait until tomorrow for pictures, as it is past sunset here.

I don't think there is anyway to move it if you can't dig out the spirea. I highly doubt there is a volunteer ash tree. You could cut them to the ground and propogate them cuttings.

If you could post pictures we could tell you what trees they are. They may just not be worth keeping. For example, Tree of Heaven leaves could be mistaken for ash.

BTW Ash frequently self seeds via winged seeds. As do Maples.

I would take some sort of tool and poke around the perimeter of the sprout until you find the main root. In my experience volunteers like this always have a very strong, very deep taproot, and once you find that just slowly excavate with your fingers until you get to a point that it can be pulled. Have the pot and everything ready and waiting, including some water- don't let it dry out or sit exposed.

I have spirea and know what a horrible task it is to have to stick you face into them to weed or dig around the base, but it can be done if you don't mind getting poked in the face. You may have to do much of the task by feel, but if sufficiently motivated you will find a way.

It has a little trunk about as thick as my pinky finger or so

This second one (growing next to the mini Ash on the right) has different style leaves and it's trunk is thinner

I had forgotten about this one. It's growing right out of the center of all the Spirea, in a bare spot that was between where they are placed. Oak?

The building is position facing directly south and the Spirea are in the shade of the building for most of the day (the edge of the woods is about 15 feet from the bushes). I think that's why they have that paler green color. My neighbor's Spirea are much better-looking but hers get more sun, as they are placed at the corner of the building. Hers are much larger and greener. I don't know if anything could be done to improve mine. Also hers don't have tiny trees in them. The tree that sheds the seed pods in Autumn is close to my bushes at the edge of the woods. They are like a seed with a wing and there's always lots of them falling and spinning through the air at that time of year. They look like this picture I found on Google:

Here is another thing that is not Spirea but is growing among them. Not sure what it is:

carp elm.. ridiculous seeder ... not ash

and it looks like a sweet gum.. liquidamber ... crush a leaf... what do you smell ...

ken

Yup, elm, ash and likely sweet gum. The google pic is box elder. I know less about the sweet gum, but any of these others are super-common volunteers in shrubbery.

I wouldn't bother with the elm-it looks like Siberian elm-not so great a tree. The ash, well......where are you? EAB ya know. Box elder-out of the question.

Should you decide all the same to go through the trouble, wetting the soil well can help slip that root system out of there. But then what? Potted? I just don't see a point to any of this, although recovering volunteer trees-where its' something you want-does make sense to me. But trees in little pots, not bonsai or any specialized treatment.......I see no point. They can't stay long in little pots, and real big pots are eventually impossible to deal with.

i dont recommend any tree that self seeds itself into a garden ... they are not quality trees because of such.. in many circumstances ...

i can pull a lot of small trees out.. in spring.. when the soil is soft and moist from winter ...

but part of your problem might be.. the fact that they were cut back repeatedly.. so there might be a rather massive root mass ... compared to size ...

i would also not bother with anything over about the thickness of a pencil ... else you are going to have to be talking about some big pots .. which means investing a lot of money in good tree media ... you wont get far.. with dirt in a pot ...

if you want to experiment with trees in pots ... just look around and find some smaller versions ... if these free seeded.. there ought to be smaller ones... for the potting project ...

i would just cut these down to near ground.. and drip or paint undiluted round up or generic on them.. and be done with it ...

i see nothing wrong with the spirea ... except maybe water competition ... i wouldnt bother doing anything with them.. except getting the trees out of them ...

ken

@Caldwell Home & Garden: Did you mean I could just cut the mini trees and then plant the cut trees in a pot and the cut tree would grow new roots? Would that risk killing the tree? Also I had been planning to plant the trees in leftover Miracle grow potting soil that I'd used for a mini Christmas-type tree but then had read on another website last night that you shouldn't use potting soil for trees. Is that so? The little Christmas tree isn't doing the best. I wonder if it's because the potting soil? I had sent a message to the grower (whose farm produces the trees) on Facebook, asking advice about the tree, but they never replied. I have no idea the species of the tree so I couldn't look it up online. The growers website doesn't say what type of trees they are either. It is some type of evergreen but not a Spruce.

@wisconsitom I live in the northeast of USA. I just thought the tree was cute so I wanted to keep it. I thought you could grow them in pots and they wouldn't get bigger because they were in pots. I had some planter pots that were like 18 inch that I thought was big enough for a small tree. I would love to garden but I never did before and don't know anything about it. My landlord said the tenants could only have stuff if it's in a pot. I tried growing mini roses, then Mums, but they all died and did not grow back the next year. I thought at least the tree would survive Winter and I'd still have it the next year. I just wanted a little greenery at the patio area that wouldn't die on me lol

Cut it, put it in a glass of water in an area where it can get sun (indoors). Change the water out weekly, and eventually it will grow roots. I have done this successfully with many things, but it is not certain that it will grow roots. Start another thread about the Christmas tree.

also I think that all the tenants have the same type of Spirea planted beside the patio areas so I did wonder why the neighbor's (at the corner) are so much larger and darker in color. The neighbor that is right beside me also had Spirea that were doing poorly, scrawny looking and pale green color like mine, until they died and the landscaper removed them but didn't plant anything else. Mine were better looking but one died away and the landscaper removed it and didn't plant anything in it's place. I don't want the rest to get worse-looking and die also. Could they be fertilized or something? Would anything make them grow healthy and fuller?

You mentioned them staying the same size, are you interesting in trying to bonsai them?

as far as spirea goes, if they die pull them out. I saw some nice loropetalums at walmart the other day for $5 each. There are many other, better shrubs that could be used in place of the spirea, fertilizer only stresses a plant more.

None of those three are trees that I would expend any effort to save.... I'd cut them off and apply full-strength glyphosate or an appropriate broadleaf herbicide to the freshly cut stem.

But... if you're determined to 'save' them... wait until they go dormant, then dig them out. and pot them up... but don't expect them to 'stay small' just because you have them in a pot.

And... I can assure you that if you cut them off and stick them in a glass of water, THEY WILL NOT GROW ROOTS.

Now I understand what's going on here, I'd strongly agree with just cutting the tree seedlings off as low as I can and daubing a bit of glyphosate on there. Use the product at around 33% and higher AI concentrations. Even if you really wanted a green ash sapling, once you start looking around, you'll see some in better positions for being dug. That right-in-a-shrub thing is vert common though!

Right, +oM. It's a sure bet that the OP could find isolated, easily-lifted (once dormant!) volunteers of all three of those species with not a lot of looking around.

I'm sure the side of the interstate is full of these crap trees! That one looks like a hornbeam, which reseeds often but is a nice addition to the landscape.

I wish I could plant something else besides the Spirea but the landlord is very strict with a lot of "rules" and specifically prohibited planting anything in the ground (only in pots). The Spirea were already here when I moved in. They seem to attract flies and are not really the nicest-looking landscaping greenery. Something that flowers would be nice. I seem to have a black thumb though so if I grow something in a pot myself it would have to do well in shade and be low maintenance. I had got the evergreen shrub for my front door area, thinking that at least it would always be green, but I apparently can't even keep an evergreen green. There are brown areas even though I water it so heavily. I noticed the little trees grow like a weed without effort and always thought potted trees were cute. I had a small ficus once but it died indoors and I don't think they are the type that would not die in Winter in our climate (at the time we lived at an apartment that had few windows and no patio and got poor sun due to the windows placement).