Avium ‘Plena’ (Prunus avium ‘Plena’) (double-flowered mazzard cherry). Prunus avium, the cultivated European sweet cherry, is a very robust, adaptable (even weedy) tree that forms a large rounded crown with distinctive branching and coarsely serrated leaves. One of the identifying features of this species is the strongly reflexed calyx that backs the almond-scented white flowers. In Prunus avium ‘Plena’, the flowers are fully double and very showy. Flowering time is late April. Trees produce no fruit, so are not weedy.