An avid fan of flowering Malus, Karsten collected many seeds from ornamental Malus over the years. Malus toringo 'Aros' came to the forefront of his breeding: a dark purple/black leaved, disease-resistant crab apple with a tight columnar habit. In spring the tree is adorned with dark pink and white flowers and in autumn small deep red crab apples persist into the winter. Its compact nature is perfect for smaller gardens and containers for spring flower, summer foliage and autumn fruit.
It is one of the entries for the RHS Chelsea Plant of the Year competition 2018.