Unlike the white mulberry, there is really only one variety and few cultivars of black mulberry.
Shape: Medium-sized tree (up to 12 m) with a short trunk and long spreading branches, which are often supported on props in older trees. Mature trees very often lean at an angle, like the Tower of Pisa, and trunks can even be nearly horizontal. Branches often have lots of thin, bendy twigs at the ends.
Bark is orange-brown, often gnarled with large burrs and fissures.
Buds are alternate, dark and pointed, opening very late (May).
Flowers are small, green, spikey catkins. Mulberries can have both male and female flowers on the same tree, but they can also be on separate trees.
Leaves are about 8 cm long, coarse, heart shaped, with toothed edges. Can be hairy on top and downy underneath. Some lower leaves and those on new shoots can be lobed, or with deep incisions. There can be several different leaf forms on a single tree.
Fruit looks a bit like a large blackberry or loganberry. These "berries" are really drupes, consisting of a cluster of tiny fruits, each with a seed. Starts green, then turns pink and dark purple when ripe (July-September in Britain). Delicious, sweet/sour, very juicy and stains fingers and clothes!
Unlike the black mulberry there are as many as 16 recognised species of white mulberry and dozens of cultivars, selected for feeding silkworms. The national mulberry collection at Buckingham Palace has 34 named varieties of mulberry, but only 8 species and sub-species. Most are Morus alba cultivars.
Shape: A slender, medium-sized, upright tree with an open crown. Grows to about 12 m.
Bark is dull grey-brown, with fissures. It can be hard to distinguish from M. nigra in Winter.
Leaves are large, and often have deep lobes, frequently three lobes a bit like a fleur-de-lys. But they can also be oval with toothed edges. In contrast with the black mulberry, they are straight where leaf meets the stem and not lobed. Usually smooth, fine, glossy and not hairy.
Buds are small, alternate and conical.
Flowers are small green spikes. Mulberries can have both male and female flowers on the same tree, but they can also be on separate trees.
Fruit: The "berries" are really drupes, consisting of a cluster of tiny fruits, each with a seed. Start green, then turn white, then pink and, in some varieties, dark red. Insipidly sweet, though some varieties (like Morus alba multicaulis) taste a bit like black mulberries.