Training a Tree To Be A Shrub
Is it possible to turn what would be a big tree into a 4-5ft shrub? I have a 12" maybe 18" sapling that I'd like to save and train into a wide flowering shrub. I believe it is an American Tulip Tree. I have a place I'd like to replant it if once it is 4feet or a bit more, I could keep it at that height and let it get wider that tall.
Baltimore County Maryland
This appears to be a sapling Southern Magnolia (Magnolia grandiflora); while its native range lies south of Maryland, they are known to occasionally germinate from seed produced by trees planted in our area. Seedlings don't always have the obvious brown fuzzy leaf backs that their parents may have had, though the leaves are evergreen. Tulip Poplar (Liriodendron tulipifera) hasn't leafed-out yet, plus the leaves have a much different appearnce. Some common names for various Magnolias include "tulip," but those Magnolia types are also deciduous and would not have leafed-out yet, nor do they tend to come up from seed.
Keeping large plants (such as 40-plus foot trees, in this case) as small as you mention is neigh impossible. Bonsai is the art of dwarfing trees to make them look miniaturized, but it is rarely done with a species so large-leaved as this because it doesn't allow for fine control over its canopy shape. Keeping this plant shrub-sized for the short term may be possible with pruning, but perhaps no more than a few years before it is stunted beyond the point at which it could be considered healthy. It is also highly unlikely a plant so pruned will produce any flowers due to its immaturity and regular pruning. There are dwarf forms of Southern Magnolia on the market, but they will still reach an eventual height of around 15-20' tall. The shortest forms of other Magnolia species tend to still be in the neighborhood of 10-15' tall.
For the height you desire, we would suggest using a flowering shrub of appropriate size instead, especially since minimal pruning to control size is less work for you and less stressful for the plant. Depending on what traits you enjoy in the Magnolia, there are many shrubs as possible alternatives.
This sapling is best either left to its own devices to mature to its normal size (even if moved to a more appropriate spot now, while young and less prone to transplant shock) or perhaps given away to someone else who has room for it.