is a Mahonia aquafolia 'Compacta' a dwarf variety of Mahonia aquafolia? If not, why not?
Multnomah County Oregon mahonia
Thank you for your question about Mahonia plants. A Mahonia aquifolium "Compactum" a small version of a Mahonia aquifolium. You can read about both of them here, which describes it as being "compact and slower-growing form to 3' tall." Thank you for using Ask an Expert.
But does the Compactum meet the horticultural definition of a Dwarf variety?
It's a cultivar ("a plant variety that has been produced in cultivation by selective breeding"). The difference between "cultivar" and "variety" is explained here. Arizona Extension describes this cultivar as follows: The most popular Oregon grape cultivar is dwarf Oregon grape (Mahonia aquifolium‘Compacta’) which resembles regular Oregon grape but is half as tall and quicker to spread by rhizomes. This is a good choice for smaller spaces where a mass of shiny, dark green foliage is desired."
You're welcome. BTW, here's another article I found on the naming and classification of plants.