The mulberry species most frequently cultivated for fruit is the black mulberry (Morus Nigra). Native to western Asia and grown throughout Europe, the black mulberry is a long-lived and decorative tree. The white mulberry (Morus Alba) is used to feed silk worms, but has inferior fruit. Mulberries grow best in sheltered, warm sites. They are tolerant of a range of soils, provided that they are well drained with a ph balance of 5.5 - 7, although mulberries do prefer a fertile, moisture retentive soil.
Mulberry tree forms and rootstocks
Mulberries in the open are best grown as, vase, standard or half standard trees. They are fairly slow growing, taking five years or so to start fruiting. Eventually they make substantial trees, needing 5- 10 metres for their natural shape to develop, and so are suitable only for large gardens, unless constantly pruned. In cool areas, mulberry trees benefit from training as an espalier, where they need a space 4.5 metres wide and 2.5 metres high. Mulberry trees are usually grown on their own roots or grafted onto seedling rootstocks. There are no dwarfing rootstocks available.
Mulberry trees are self fertile and therefore need no cross polination from other mulberry trees. They flower relatively late and therefore tend to escape the effects of frosts.
Planting mulberry trees
Plant mulberries in the dormant season. Bare root plants usually establish well. Container grown mulberries also grow away well if they are not pot bound. For a standard or half standard tree, try to buy a part trained tree to obtain a well formed tree more quickly.
Pruning a mulberry standard or half-standard tree
Prune mulberries when they are fully dormant, cutting in the growing season results in bleeding from the wounds. In the winter after planting, remove any shoots that spoil the shape, and any on the stem below the framework branches. Repeat in early to midwinter each year, removing any poorly placed shoots for a good framework. Once the mulberry tree is established, little pruning is needed, simply remove any crossing, crowding, dead or broken branches.
Pruning mulberry espalier
Formative pruning of an espalier mulberry tree is undertaken in early to midwinter. Once the tree is established, prune lateral shoots arising from the stem and branches of the espalier in late summer, when the growth has slowed down, shortening them to three or four leaves to produce fruiting spurs.
In late winter each year, apply a general compound fertiliser at 70 grams per square metre over the rooting area. Apply a mulch or organic matter such as well rotted manure, compost or bark in spring. Give extra water during dry periods in the spring and summer for the first 3-4 years after planting, after that mulberries should grow with minimal irrigation. The branches of mature trees may become brittle, so it may become necessary to provide support by driving a forked stake into the ground and resting the branch on cushioned sacking in the fork.
Mulberry yields are very variable. The mulberry fruits mature over a few weeks in mid to late summer, and are almost black in colour when ripe, parting easily from the sur. For preserving, use slightly under ripe fruits. Take care when harvesting as the juice stains clothes easily. For large mulberry trees, spread a cloth beneath the tree to catch the fruit, and then gently shake the branches.
Mulberries are not commonly bothered by pests and diseases although birds will often take fruit, creating a need for a net to be cast over the mulberry tree.
When purchasing a mulberry tree, try to choose from these named mulberry selections rather than unnamed seedlings thus ensuring a better plant.
Black English – Red / black mulberries, sweet acidic taste, long fruit. The flavour of Black English mulberries tend to be superior to that of Hicks Fancy.
Hicks Fancy – Red juicy mulberries, sweet but acidic, tend to grow quicker than Black English varieties.