There is a very large amount of variation among seedling mugo pines as to their mature size, as well as needle size. Dwarf in the name will not tell you enough. If you wish to be certain that a mugo pine will stay within the size range you want, it is wise to purchase a named cultivar with the desired characteristics. Grafted plants will cost more than seedlings, but can save homeowners much grief.

I love mugo pines, but they are not commonly grown here. They don't really like our climate.

We have a Slowmound Mugo Pine. It's the third growing season for it and it has definitely lived up to its name so far. The growth rate is about 3-4 inches a year.

there is a very active conifer forum ...

but i will answer you here ...

first... as noted.. there is no predictability unless its a named cultivar .... and with said name.. you could research growth rate and size potential ... ...

and.. though an exaggeration ... i like to say.. for impact. .. that if momma has 100 foot potential.. a dwarf of her.. might only grow 75 feet ...

a true dwarf.. is supposed to grow.. 3 to 6 inches per year... you should be able.. since pine has one growth spurt in spring .... to look at any given pine.. and find out how much it grew last spring.. and simply presume... that is the MINIMUM annual growth.. and once established in the ground.... could be much more ...

most size estimates are at 10 years... based on that annual growth rate ... and you can presume.. at 20 years.. they will be twice as large.. because.. as trees [NOT SHRUBS].... and as conifers [NOT SHRUBS] .. they really NEVER stop growing.... because.. they are.. wait for it.. NOT SHRUBS... lol ...

i have some 5 year old MINIs ... that are barely bigger than a dinner plate ....

but let me sum it up this way .... of my 600 odd conifers.. two were purchased at bigboxstore ...

peruse the pix at the link.. to see the great variability ... on your words alone.. and do understand.. that the smaller of them ... are not un-named bigboxstore plants ...

in the conifer forum .. there are some very current posts.. on preferred providers ....

ken

Here is a link that might be useful: link

Thanks to all for the help you have given. The site full of pictures show the various looks we can have. Decisions decision ! Thanks again. I will study this a bit longer.

I got a dwarf mugo pine in the bargain bin at lowes. It has some brown branches, but some green ones. What would be a good use for it? I could plant it with some dwarf alberta spruce, holly and hydrangea, or I could incorporate it into foundaton planting close to the house between yew and diablo ninebark. Which would look good?

Get a grafted one that says Pumillio. That Group has several dwarf forms.
Be careful in siting it so it doesn't get lost in the garden.
Mike....not a fan of mugos.