Someone gave us a black mulberry start years ago in the Dominican Republic and we wanted to take a start with us when we moved to Puerto Rico. But one cannot take live plants through the airport. So, we cut some woody stems (bark covered, rather than green stem), and packed them in our moving luggage with the chopsticks and bamboo cooking implements, where they passed muster as sufficiently dead-looking. A few days later, we stabbed them into moist dirt and kept them watered for a while (a month or so, as I recall) until they sprouted. They have each survived three years in poor soil and begun to bear fruit.
Mulberry, as far as I can tell, do not produce seeds (though my experience is limited to Morus nigra). So they are not the sort of plant that agricultural agencies need be worried about invading a non-native habitat. They are very robust - in north america they are found from the tropics to the latitude of Vancouver, though not in the northern Rockies so much. In europe they prosper from southern Spain to Denmark. In asia they live north to northern Japan and China. In the southern hemisphere, they are found south to Argentian, South Africa, Tasmania, and southern New Zealand. I guess in a sense, they have invaded quite well . . .
