Robin Gale-Baker, from Sustainable Macleod, discusses growing mulberries. This is one of a series of articles she has written about growing fruit trees (see right hand sidebar). She has also written a number of articles about growing various vegetables, growing various herbs and general growing techniques.
It’s November and it’s therefore mulberry season! Those lucky enough to have a mulberry tree will no doubt be currently enjoying a bountiful crop – that is, if they beat the birds to the dangling berries.
This article is about red (Morus rubra) and black (Morus nigra) fruiting mulberries. If you want to grow a white fruiting mulberry, choose the white shahoot (Morus macroura) – read Jaimie Sweetman’s article about the white shahoot. Do not choose the inedible common mulberry (Morus alba), whose leaves are fed to silkworms.
Before deciding to plant a mulberry, note that both the red and the black species will stain any surface under and surrounding the tree. They will also stain your fingers, but you can rub them with a wet mulberry leaf to remove the stain.
The main varieties of the black mulberry in Australia are Black English and Hick’s Fancy (the latter having smaller fruit). The main variety of the red mulberry is Downing’s Everbearing.
Habit and conditions
The mulberry tree is a vigorous grower which prefers fertile, well-drained soil and a temperate climate. It does not like wet feet but needs water in summer if conditions are dry. Wherever it is planted, it is likely to be in full sun given its aptitude for quickly heading skyward, with particularly rapid growth in its first few years. Mulberries can grow up to 15 metres in height and 8 metres in width so are unsuited to small gardens.
An alternative is to plant a weeping mulberry, which will grow to a height of 2-3 metres and width of 3-4 metres but can be pruned to keep it smaller. They can also be kept in pots or espaliered.
The best way of propagating a mulberry is by making hardwood cuttings in Spring. Dip them in hormone rooting powder and insert them into a mix of vermiculite and perlite. Another way, if there are branches close to the ground, is to bury some branches so that only two buds stick out above the earth and eventually uncover the branches, sever the rooted section and re-plant.
Mulberry trees can produce multiple trunks. If so, then either reduce to a single, selected trunk or think about staking for stability.
Mulberry trees can ‘lean’ and this can be dangerous. If the tree leans then it needs to be assessed for safety and steps taken to remedy the situation. If the lean is more than 15 degrees, the tree is unlikely to be able to be rehabilitated.
It is recommended that fertiliser be added in spring. If the leaves yellow and/or fruit drops prematurely, then that is an indication that fertiliser is needed.
This is a thorny subject with a lot of conflicting advice from experts.
Generally, the advice is to prune in winter. However the tree will then grow considerably in Spring and often the purpose of pruning is to reduce the size of the tree. In reaction, sometimes winter pruning is followed by a light summer prune after fruiting but this can be either difficult or impossible if the tree has grown too high.
Personally, I follow the advice from Grow Great Fruit in Harcourt, Central Victoria, to prune two major branches from my tree in summer as this is the time that there is little vegetative growth and pruning then will keep my tree smaller. It takes patience and the shape of the tree won’t be symmetrical for some time but it is working for me. As pruning of thick branches produces bleeding, I wait for a dry, windy period so that the wounds will dry quickly and prevent entry of disease.
Always, when pruning out thick branches, cut at the junction with the trunk. In line with good hygiene practice, prune out any dead, diseased, damaged or crowded wood. Open up the centre of the tree for good air circulation which will not only prevent disease but also allow the sun to ripen the berries toward the bottom of the tree. Berries that are shaded do not develop sweetness and are very bland.
Pests and diseases
Birds are the biggest problem and they can ‘clean’ a tree quickly when the fruit is sweet.
In humid climates, mulberry trees can suffer from fungal or bacterial diseases but we don’t have sufficient humidity in Victoria for this to be problematic.
The best way to harvest is to spread a tarpaulin beneath the tree and shake the tree!
Mulberries only last a couple of days after harvest so use them quickly or freeze them. They can be used in pies, muffins, jam, syrup, juice, ice cream or eaten fresh.