Moraceae

 

A large Family of some 1400 species attributed to forty genera. It is principally tropical and subtropical in distribution and contains entities from herbaceous plants (although somewhat woody) to trees. They are usually evergreen; however there are three woody genera with chiefly temperate climate distributions - which are deciduous.

 

The Family contains Artocarpus (Breadfruit and Jack Fruit) and the Figs (Ficus). The genera containing species with a temperate provenance, addressed here, are Broussonetia (Paper Mulberry), Maclura (Osage Orange) and Morus (the Mulberries).

 

These three relevant genera develop ‘multiple’ fruits which consist of an aggregate of one seeded, fleshy drupelets. In general they are fast growing – especially in the juvenile stages.

 

Morus

 

The taxonomy and nomenclature of Morus is confusing and unclear, it is usually determined as ‘10 to 16 species’ but in practice there are a few easily defined species which include M. alba, M. microphylla, M. nigra and M. rubra and a whole series of indeterminate entities (designated as species) occurring in South East Asia including M. bombycis and M. cathayensis. In this latter group hybrids are common and they in turn are often fertile – so producing a nightmarish taxonomic scenario!

 

The genus is deciduous and has a temperate distribution which fringes into the sub-tropical in South East Asia. The species are usually dioecious (sometimes monoecious with flowers on different branches). The inflorescences consist of compound, inconspicuous, oblong catkin-like flowers that are produced in April-May; each fertilised ovule develops into a one-seeded, fleshy drupelet and these aggregate to form the familiar berry-type, multiple fruits.

 

As the fruits ripen they change colour from pink through red to dark purple - the  fruit juice stains dramatically, so that siting trees should be determined to avoid situations where this could be a problem. The fruits ripen in July -August and are some 2cm across; they consist of 12 to 14 drupelets. Each has a very thin, membranous coat and the seed is protected by a bony endocarp which, however, is not generally impervious to water. Although the fruits may be formed properly the seed are often void if a pollinator is not present. The fruits are taken by birds.

 

The fruits can be easily picked (wear gloves!) from the tree or from the ground. The seed is readily extracted from the ripe fruits by maceration and the detritus, which floats, is separated in running water. There is some evidence to show that, if the fruit is fermented for a couple of days, any marginal ‘hard seededness’ which may have developed is eliminated. Normally it would be prudent to give all samples of seed a 48 hour warm water soak prior to treatment.

 

All of the temperate species benefit from at least a short chill - which synchronises and speeds germination. Morus alba and M. rubra should be chilled at below 5˚C for 35 days while the colder provenance M. nigra needs up to 63 days at 3˚C. As the seeds are capable of radical emergence at low temperature, the lots should be regularly monitored and if chitting does occur then they should be transferred to suitable temperatures (20˚C) for speedy germination.

 

The seedlings are generally fast growing in their early years but quickly settle out to develop a slow growing habit with an often dense and gnarled appearance

 

The seedling roots are fleshy and brittle so care should be exercised in subsequent handling.

 

Broussonetia

 

This genus of deciduous trees and shrubs is closely related to Morus; it contains four species native to Eastern Asia – Japan, China and Korea through SE Asia to India. All the species have a pioneer habit and are capable of being invasive. The species most often encountered is B. papyrifera – the Paper Mulberry from China and Japan (in Japan the bark is used for making paper) – it is suitable for cultivation in the UK but in parts of the World (eg Pakistan and the Pampas of Argentina) this potential for invasiveness has made it a pestilential weed. B. kazinoki from Japan is also sometimes cultivated. Because these species are dioecious it is necessary to grow several plants if the fruits are required.

 

The plants flower in April-May - the male flowers are catkin like and on established specimens are prolific, the female flowers are globular about 2cm across with long, hanging styles. The fruits which are orange-red are produced from August onwards, they are spherical, multiple fruits made up of one-seeded, fleshy drupelets. The flesh is soft and the fruits are taken by fruit eating animals and birds.

 

The seeds are extracted by maceration and then the detritus can be floated off in running water.

 

The seeds germinate readily at temperatures above 20˚C and there is some evidence that light is beneficial.

 

Maclura

 

Maclura is a monotypic genus (M. pomifera) – the Osage Orange – it is a native of the United States - originating in the Red River Valley but is now naturalised over much of the continent as a result of its use (on government recommendation) as an agricultural ‘stockproof’ hedge during the nineteenth century. It is a pioneer species and can grow into a tree to 15m tall. It is deciduous and the simple leaves each subtend a spine – 2 to 3cm long and which is quite formidable. It is hardy enough to succeed in cultivation in most of the UK but as the plant is dioecious; seed production depends on the presence of plants of both sexes.

 

The inconspicuous flowers are produced in early summer. The female trees may still produce normal looking fruits - even if not pollinated - but the drupes are seedless.

 

The fruit is a ‘massive’ globular unit – often up to 15cm in diameter. It consists of an aggregation of one-seeded drupelets which are coalesced on the surface (making it bumpy in appearance) and the centre of which is filled with a white latex type material. This fruit is initially green but becomes yellow at maturity.

 

The seeds are extracted by harvesting the ripe fruits – slightly macerating them and then leaving them to ‘rot’ and ferment slightly in a warm situation. The whole mass can then readily be squashed in water, gently macerated and the seeds separated and washed clean.

 

The seeds can then be surface dried when they can be stored in the short term at cool temperatures. Germination will occur without pre-treatment but the most satisfactory and productive germination will occur if the seeds are given a 24 hour warm water soak and the chilled for 35 days at 5˚C and then germinating at 20˚C.