With the white mulberry this one is Mulberry Red (Morus Rubra), and is also one of the first top fruits of the season grown outside.
Morus Rubra is a tree which can reach 15m high x 15m spread but, in its cultivated form, is often coppiced, pollarded or pruned to a low-growing bush to facilitate the harvesting of fruit or leaves.
For pollination the tree can get a bit mixed up, some years its male, some female and some mixed. It is therefore best to have another for pollination to be successful and they are wind pollinated.
Mulberries thrive in full sun and dislike crowded conditions; they prefer deep soils and need good drainage; they are frost resistant to zone 7.
The texture is very much like a blackberry. The fruit on this tree is the size of a pea, but the sweetness is so intense.