The Essential Guide to Mulberries

Paul Alfrey - Balkan Ecology Project
Friday, 29th September 2017

All you need to know about the three types of mulberry. From habitat, feeding, irrigation, yields, pests, its uses in agroforestry and more.

Not many plants offer so much to the grower while demanding so little in return. A tree that requires so little attention and care, that even if there were an RSPP - Royal Society for the Protection of Plants (which there should be judging by the amount of tortured house and garden plants I come across), no-one would ever get prosecuted for Morus neglect.

Mulberry is one of the fastest growing temperate trees I know of, produces an abundance of excellent fruit every year and is virtually pest and disease free. It is one half responsible for the finest fibres known to man, i.e. silk, can be grown nearly anywhere that has soil and is a source of high quality animal fodder, plus quite a bit more, as we shall see.

Here we'll take a close look at these incredible plants including how to grow them, the uses of Mulberry, growing Mulberry in polycultures, permaculture and agroforestry and i'll introduce some relatively rare Bulgarian cultivars that we are offering from the bionursery this season.   

Overview

There are about 68 species of the genus Morus, and the majority of them occur in Asia. In China alone there are over a thousand cultivars grown.

We'll be focusing on the White Mulberry - Morus alba that we grow in our gardens and we'll also touch on Black Mulberry - M. nigra and Red Mulberry - M. rubra, two other popular plants in cultivation. Let's start with an attempt to clarify the differences between these three species and then take a detailed look at White Mulberry.

The differences between Red, Black and White Mulberry 

  • White Mulberry is native to northern, eastern, and central Asia and is one of the primary species used to feed silkworms.
  • Black Mulberry is native to southwest Asia. It was brought to Europe before the Roman Empire where it has continued to be grown for its fruits.
  • Red Mulberry is native to eastern North America.

There is a fair bit of confusion over these three species. The colour of the fruit does not identify the mulberry species. White Mulberries, for example, can produce white, lavender or black fruit. White Mulberry fruits are generally very sweet but often lacking in tartness. Red Mulberry fruits are usually deep red, almost black, and in the best cultivars, have a flavour that almost equals that of the black mulberry. Black Mulberry fruits are large and juicy, with a good balance of sweetness and tartness that I personally prefer the most.

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White and Black Mulberry fruit

Black Mulberry can be distinguished from White Mulberry by a hairy lower leaf surface on the Black Mulberry plants. The juicier Black Mulberry fruit will also stain your fingers when you pick them. The fruits of the White and Red Mulberry are more difficult to tell apart but a sure way is from the leaves. The upper surface of the Red Mulberry leaves are noticeably rough, similar in texture to fine sandpaper while in stark contrast the upper surface of the leaves of White Mulberry are lustrous (glossy, smooth and shiny).

Confusing the situation further, Red Mulberry and White Mulberry often hybridize, resulting in trees with intermediate characteristics.

According to Ovid (Metamorphoses - Book IV) you have the Babylonian lovers Pyramus and Thisbe, and the Greek Gods to thank for at least some of this confusion. In short, Pyramus and Thisbe denied their love of each other by their rivaling families decided to run off together (sound familiar?). The rendezvous was under a White Mulberry tree out of town. Thisbe turned up first and while waiting for Pyramus, a lioness with jaws stained from the blood of a previous kill started towards her. Thisbe darted into a nearby cave dropping her shawl under the tree as she fled. The lioness approached the shawl, dripping blood all over it just as Pyramus showed up. Pyramus chased the lioness away and seeing the blood stained shawl assumed that Thisbe had been mauled to death. In desperation he plunged a sword into his belly just moments before Thisbe emerged from the cave. Finding Pyramus taking his last breath she falls on the sword herself and they both bleed out in tragic unity. The blood splashing from the bodies stained the previously White Mulberry fruit, and the Gods forever changed the Mulberry's colour to honour their forbidden love. All I can say is thank the Gods for mobile phones.

White Mulberry - Morus alba

Latin name - Morus alba
Common name - White Mulberry, Silkworm Mulberry
Family - Moraceae

History - White Mulberry cultivation has a long and rich history dating back thousands of years ago as a requirement for silkworm rearing. They were beloved by Persians, Romans and Greeks and moved throughout Europe along with the spread of culture from these places.

Growing Range -  Morus alba has a very wide distribution range in Asia and Europe (from Korea to Spain, including China, India, Central Asia and the Near East); in Africa (North and East Africa) and in the Americas (from the United States to Argentina, including Mexico, Central America, Colombia and Brazil). The origins of most cultivated mulberry varieties are believed to be in the China/Japan area and in the Himalayan foothills.


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Morus alba leaf variation - https://en.wikipedia.org/wiki/Morus_alba

Description -  A fast-growing, small to medium-sized tree growing to 10-20m tall. It is generally a short-lived tree although there are some specimens known to be over 250 years old. Fruits can be white at maturity on a few trees, but are usually dark purple and 3 to 6cm long. The fruits ripen from mid spring - late summer (depending on species and cultivar). The leaves are usually shiny, dark green and smooth but can be yellowish green. Most leaves are not lobed, but some can be. The juvenile growth is often lobed.

Sexual Reproduction - The trees can be dioecious or monoecious, and sometimes will change from one sex to another. The flowers are held on short, green, pendulous, catkins that appear in the axils of the current season's growth and on spurs on older wood. They are wind pollinated and some cultivars will set fruit without any pollination. The White Mulberry is notable for the rapid release of its pollen, which is launched at over half the speed of sound!

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Mulberry flowers - in some cases the male and female flowers are on the same tree (monoecious) and in other cases the male and female flowers are on separate trees (dioecious).

Light Preferences - Mulberries thrive in full sun but can grow well in partial shade.

Water needs - The plants are drought tolerant but grow best and yield high in areas with rainfall between 600 -1500mm/yr. In our location with average annual rainfall of 580mm they grow well without irrigation. I have seen Mulberry growing well in wetlands and on riverbanks, as the plants are tolerant to sporadic water logging although they usually occur in non-wetlands. 

Habitat - Morus alba commonly invades old fields, roadsides, forest edges, urban environments, and other disturbed areas. It grows well in natural forests, planted forests, range/grasslands, ruderal/disturbed areas and urban areas.

Hardiness USDA - 4b - 9a  A very hardy tree tolerating temperatures down to -36oC but also comfortable in sub tropical and Mediterranean climates. Morus alba is the most cold resistant of the Mulberry trees.

Ecology - Many small mammals feed on mulberries, including birds, foxes, squirrels and rodents. Deer browse on the twigs and foliage and a range of insects inhabit the crowns of mature trees. In our experience Ladybirds are attracted to the Mulberry fruit. Mulberry is often associated with mycorrhizae including Glomus mosseae and Glomus fasciculatum.     

Where to Plant

Climatic Limitations - Mulberries thrive over a very wide range of climates especially warm temperate but also Mediterranean, sub-tropical and tropical, where they can be grown as evergreens.

Soil - They prefer a warm, moist, well-drained loamy soil in a sunny position. However they are adapted to coarse, medium, and fine soils. They tolerate a pH range of 5.0-7.0.

Location - The trees are tolerant of wind, drought, cold and partial shade so you can pretty much plant them anywhere. The plant is also quite salt tolerant once established. A few things to consider when choosing a location is that the fruit fall can extend 6-8 weeks and once mature it's practically impossible to harvest let alone consume all that fruit, so placing the tree in a place where the fruit fall will not be a nuisance is a good idea. Much to the pleasure of our pigs we set their pen under one half of our Mulberry tree with some of the tree overhanging the chicken coop also.

The trees can get large and will cast a heavy shade when mature so this should also be taken into consideration. We lift the lower limbs of our trees to allow space and light for a range of smaller trees, shrubs and herbs (see Mulberry polyculture later).

Pollination/Fertilisation - Some cultivars will produce greater yields if allowed to cross-pollinate, although many cultivars (monoecious types) do not need cross-pollination at all. Some Mulberries can even produce fruit without any pollination. Pollination occurs by wind.

Feeding, Irrigation and Care

Feeding - Mulberry require little fertilisation. When planting out new trees top dressing the planting hole with  20 - 30 L of compost and repeating this in early spring for the first 2 years will be more than enough to get them going. After this they should be fine, especially so if you are growing the tree in polycultures.   

Irrigation - The trees will grow faster and produce more fruit with access to water during the flowering and fruiting period. Young trees should be mulched well each spring and irrigated for the first 2-3  years with 30 L of water every 2-4 weeks without rain. The trees develop deep taproots that should be able to access ground water if available.   
  
Weeding - Mulching plants with a 10 -20 cm deep mulch each spring and pulling weeds that start to grow through in the summer is good practice when the plants are young. As the trees mature they grow well amongst other plants of all kinds.

Pruning -  Mulberry are low branching. We have lifted the lower limbs of our trees to approx 5- 6 m high allowing us to plant under the tree and to allow easy access around the tree. The trees respond well to this type of pruning. If pruning young trees bear in mind the flowering and fruit buds develop on second year old growth.

Harvesting - The easiest way I know of to harvest a White Mulberry is the shake and catch method.

Fresh fruit only keeps for a few days, and is best kept refrigerated if you don't eat them immediately. This is one of the main reasons you don't see much Mulberry fruit in the shops. The fruits can also be dried or frozen (never tried it personally).

Propagation - There are many reports on the internet of how easy it is to propagate mulberry from branches. Simply cut the branch from the tree and push it into the soil and presto! it will root within a season. I've tried this many times with our White Mulberry Morus alba  trees with no success. In fact I have tried hard wood cuttings in every season with no successes. It seems to me that this method is probably effective method for Red Mulberry and perhaps Black Mulberry.

White Mulberry can be grown from seed and is best sown immediately after fruiting. Cold stratification for 4-16 weeks can improve germination rates. Layering is also reported to work well.

Potential Problems 

Invasive - This species is considered ecologically invasive in most of North America. The threat is to the native Red Mulberry (M. rubra) though hybridization. It does not seem to be a problem in Europe.


Pest and Disease -  Mulberries suffer few disease and insect pests. I have never experienced any problems with the Mulberries we grow or any I have seen. It's an oddity that based on this more people do not grow them at home and commercially.  The main pest to Mulberry is probably deer that will browse on the leaves of these plants, but this is generally only a problem with young trees and regrowth from coppice. If you are growing for biomass pollarding the trees at a height the deer cannot reach is a good solution.

Allergies - The plant's pollen has become problematical in some cities where it has been blamed for an increase in hay fever.

Mulberry Yields

Trees grown from seed will start to fruit in the 5th or 6th year. Cultivar whips should start to fruit in the 2nd or 3rd year.

Younger trees can be expected to yield between 3-5 kg in the first 2-4 years when fruiting begins. A mature tree of 20-30 years will produce well over 300kg of fruit.

To harvest the trees we hold a net under and shake the branches. As the fruits ripen at different stages starting in early June and ending in early August inevitably you shake down some unripe fruit but the majority of the fruit is in good condition.

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Harvesting Mulberry with nets in our garden

If you coppice or pollard the tree you will need to wait a year before they start to produce fruit again as the flowering buds are borne on the second year growth. 

Mulberry Polycultures 

Mulberry are excellent plants for use in polycultures. They are tolerant of partial shade so suitable in the edges of an under storey of a larger tree, are not very nutrient demanding or competitive. They tolerate pruning very well and can be used for chop and drop plants grown between fruit trees or in hedgerows. If fruit production is priority they can be given a position in full sun and although they grow tall and wide, by lifting the lower branches you can accommodate a range of productive and useful plants underneath them.

Perhaps one of my favorite polycultures in our home garden features a grand old Mulberry tree - Morus alba. The tree is approx. 10 m tall and 12 m wide. As previously mentioned the mulberry overhangs the pig pen and some of the chicken coop. The slow but sure delivery of  fruit fall for 8 weeks in the spring and summer is much appreciated by the animals.

On the edges of the canopy we have a fig tree and a Cornelian Cherry that both produce exceptionally well and we have planted a few hazels on the south side last year.

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Figs and Cornelian Cherry from the Polyculture

Directly under the Mulberry tree there is an Apple and a Pear tree. Both trees are semi standards but the shade of the Mulberry has resulted in the trees taking on a dwarf habit. The Apple produces a negligible quantity of small red fruits (we keep it as it serves as part of the electric fencing in the pig pen) but the Pear tree on the western side of the tree produces a reasonable quantity of delicious Pears.

Under and around the Pear we grow  Asparagus plants with Chinese Lantern and Tuberous Comfrey ground cover and we have a few black currant plants. Finally there are two patches of Raspberry one to the north of the tree and one on the eastern edge of the canopy.

We also have 4 raised beds to the east of the mulberry where we grow tree saplings that appreciate the shade of the Mulberry during high summer.

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Tree seedling beds under the mulberry. You can see the lifted Mulberry canopy on the top left corner of the photo.

I'll be making a detailed write up of this polyculture in the near future.

Agroforestry Potential Of Mulberry 

There is great potential for Mulberry in agroforestry systems. It's deep-rooting habit and drought tolerance makes it a suitable tree for Alley cropping with grains grown in between alleys. The fast growing nature of the tree and it's tolerance to wind makes it great candidate for windbreaks and biomass belts. Furthermore the high quality animal fodder that can be produced from the trees make it an excellent choice for silvoarable systems although the fodder is generally cut and carried as the plant is not suited to continuous grazing.

We'll be experimenting with optimal cutting intervals in our upcoming perennial polycultre trials growing the biomass for fodder and for mulch material. 

I've included mulberry in a few agroforestry designs the most recent being an alley cropping system with single row mixed contour plantings (with Hazel and Pea Tree). The alleys in between the rows will be used for free ranged pastured poultry and growing grains for the poultry.   

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26m stretch of a polyculture tree row for an alley cropping design for Catherine Zanev's farm in Debnevo, Bulgaria 

Mulberry Cultivars 

We have some great mulberry cultivars on offer this season. The cultivars have been developed in Bulgaria and are suitable for all climates where Mulberry grows well. We have a selection of heavy cropping plants as well plants grown for biomass/animal fodder or sericulture. All of these plants are resistant to all major pest and diseases.

The price is €12 per tree and we are offering 10% discount for orders over 30 trees.

Mulberry cultivars - Fruiting Plants 

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White Mulberry - Morus alba - 'Vratza 24' 

Fruit - Abundant large purple fruits ripening from June - August 
Sex and Pollination - Dioecious - Female Plant will produce fruit with a male pollinator such as 'Kokuso 27' or any fruiting mulberry nearby
Hardiness - Full hardy withstanding temperatures as low as -34oC
Leaves -  Large entire leaves (22cm x 19cm). Thick and nutritious
Fodder Potential -  The leaf yield under rain fed conditions with planting distance 3m x 1m, 3300 trees per hectare is higher than 13,000kg/ha.
Water needs - Very drought tolerant

White Mulberry -  Morus alba - 'Vratza 18'

Fruit - Abundant Large purple fruits ripening from June - August 
Sex and Pollination - Dioecious - Female Plant will produce fruit with a male pollinator such as 'Kokuso 27' or any fruiting mulberry nearby
Hardiness - Full hardy withstanding temperatures as low as -34oC
Leaves - Large entire leaves (29cm x 21cm). Thick and nutritious
Fodder Potential - The leaf yield under rain fed conditions with planting distance 3m x 1m, 3300 trees per hectare is higher than 14,000kg/ha.
Water needs - Very drought tolerant 

Kagayamae Mulberry - Morus kagayamae - 'Kinriu'

Fruit - Abundant large black fruits ripening from June - August 
Sex and Pollination - Dioecious - Female Plant will produce fruit with a male pollinator such as 'Kokuso 27' or any fruiting mulberry nearby
Hardiness - Full hardy withstanding temperatures as low as -34oC
Leaves -  Large entire leaves (25cm x 19cm). Thick and nutritious
Fodder Potential -  The leaf yield under rain fed conditions with planting distance 3m x 1m, 3300 trees per hectare is higher than 16,000kg/ha.

Mulberry cultivars - Biomass and Fodder Plants

These plants have been selected specifically for vigor and their huge nutritious leaves.

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Large leaved mulberry, great trees for biomass production for sericulture, mulches and animal fodder

White Mulberry -  Morus alba - 'Kokuso 27'

Fruit - Fruitless
Sex and Pollination - Monoecious - Majority male flowers
Hardiness - Full hardy withstanding temperatures as low as -34oC
Leaves -  Large lobed leaves (22cm x 17cm). Thick and nutritious
Fodder Potential -  The leaf yield under rain fed conditions with planting distance 3m x 1m, 3300 trees per hectare is higher than 16,000kg/ha.

Japanese Mulberry - Morus latifolia - 'Kokuso 21'

Fruit - Fruitless
Sex and Pollination - Monoecious - Majority male flowers
Hardiness - Full hardy withstanding temperatures as low as -34oC
Leaves - Large entire leaves (23 cm x 17cm). Thick and nutritious
Fodder Potential - The leaf yield under rain fed conditions with planting distance 3 m x 1 m, 3300 trees per hectare is higher than 15,000 kg/ha.

Useful links

Essential guide to hazels

Book: Trees for Gardens, Orchards and Permaculture by Martin Crawford

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Tue, 03/10/2017 - 22:33
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