the mugo pine is out growing the space that it is in. we would like to reduce it size in width and height, is this possible to do without killing the pine. what is the best time to cut back on this plant.
This is a common complaint with Mugo Pine, they are sold as Dwarf varieties but can still grow or outgrow their space.
If you shorten the stems you will likely cut off the dormant buds and this will result in no new growth and the stem will die.
You can try to shorten the longest stems back to existing interior limbs that still have needles.
If you are successful in cutting the long stems back, next spring you can tip prune the shrub on each branch when once it's 1 inch long.
This will thicken the foliage. If the proposed cuts, will leave you with little foliage, you may want to dig it up and replace it.