Propagating Mulberries

This article is an excerpt from my book, Trees of Power published by Chelsea Green

    Mulberries have been one of my favorite trees for a long time. I have always been so amazed at how much fruit they are capable of producing. I love that the fruit can leave a purple stain on fingers, mouths, and cars, that it can feed a million birds and still leave huge amounts of delicious berries for the rest of us. After a lifetime of generously dropping copious amounts of fruit from the sky, a mulberry tree will leave behind a trunk of beautiful rot resistant wood. I am intrigued by the commercial possibilities of this tree, from dried fruit to jam to poultry feed. And, I am totally amazed that mulberry trees are not widely available at nurseries along with apples and peaches. When I first tried to buy a mulberry tree, I could not find one anywhere locally, so I decided to grow my own. That was in 2008, and I have grown thousands since. Here are some of the lessons I have learned along the way to successfully propagate mulberries. Let me know if you have any questions or suggestions, as I hope to keep improving on these skills.

    Cloning vs. Seed: Mulberry trees are dioecious, meaning that some trees are male and some female. If a female tree is growing with no males nearby, the tree will make lots of fruit with either no seeds or unviable seeds, while a male tree will never fruit. Growing trees from seed means that you don’t know what sex the seedlings will be until they flower. A seedling mulberry often takes from 5-10 years to begin flowering. A grafted mulberry will begin flowering and fruiting it’s first or second year because it skips the juvenile phase by using the mature wood of an older tree. 

If you grow a fruit from seed it will produce a tree different from its parent, just like every kid is different from their parent. Some mulberry trees taste much better than the average wild tree. In order to get another tree with the same fruit, it would need to be cloned. It could be grown from cuttings, grafted, or layered. If it was grown from seed, it might be a male or a female and it might make fruit very different from its parent.

    The benefits of a seedling are that they are easy to propagate in large numbers and they increase the genetic diversity of the species, allowing mulberries to continue evolving. Clones, while rewarding to grow, are an evolutionary dead end. Seedlings are also the only way to discover new varieties. Seedlings are also highly suitable trees for wildlife, livestock, and they often produce decent fruit. The first 3 seedlings I grew to fruiting age began bearing at age 6. Each tree made hundreds of berries that year. One tree had red berries, one black, and one white. They all tasted pretty good.

A sea of mulberry trees. There are over 1,000 trees started in this 4 x20 foot bed.

A sea of mulberry trees. There are over 1,000 trees started in this 4 x20 foot bed.

    Cuttings: From literature I had read, I thought that starting mulberries from cuttings would be an easy way to start a bunch of trees. I have stuck hundreds and hundreds of mulberry cuttings using vigorous water sprouts from all times of year. I’ve gathered cuttings while they are dormant in the fall, winter, and spring, and have collected them during June and July. Most cuttings received root hormone dips. My success rate has been about 1%. The cuttings that did form roots generally made one or two very small root hairs that died after a month or two. I’m not sure why so many other people have had success with mulberry cuttings, but to me they have been impractical.

I wrote that last paragraph in 2013. I have since learned how to root mulberry cuttings. I believe that some varieties of mulberry are much easier to root than others. 

I have been able to root hardwood cuttings when they are gathered in late winter, treated with rooting hormone and placed in trays with bottom heat. I used a very light mix, that was about 70% sand and 30%  compost/soil. Hardwood cuttings have still rooted at a very low percentage for me.

Softwood cuttings have been very successful for me since I built an intermittent mist system. The cuttings are placed in beds of sand that has a heating cable underneath. A fine mist is sprayed on their tops every ten minutes for a duration of 10 seconds. I take the cuttings when they are most actively growing. I cut them into small pieces, as long as the space between each leaf node. I cut most of the leaf off, just leaving a small portion attached to the cutting. Under these conditions, I've had certain varieties root in as little as two weeks, but some other varieties never seem to root.

I understand that a mist propagation system is not for everyone. I was too intimidated to build one for a long time, but was finally inspired to by a friend who had. It has been a real joy to use and be able to produce so many plants.

A rooted mulberry cutting out of the mist bed

A rooted mulberry cutting out of the mist bed

    Seed: This has been very reliable for me. It is easy to start thousands of trees in a few minutes if a few things are given attention. The first thing to be aware of is the tree that you gather seed from. Some fruit bearing trees do not have a male tree nearby, and so any seed you find in the fruit is likely to be sterile. It is best to find a fruiting mulberry that has lots of close neighbors, this will bring seed viability to very high levels.

    Seed can be cleaned from the fruit and dried. I obliterate the fruit in a bucket of water with a paint mixer. I then pour off the excess water taking care not to dump the seeds. Add more water, stir it, dump water, add water, stir, dump, add water, stir, dump.... Eventually all the fruit pulp will have floated away and you will be left with a considerable amount of seed in the bottom.

   Mulbery seeds do not require stratification or treatment of any kind. They usually sprout within a couple of weeks.

    One catastrophe to avoid when growing seed out is slugs. They can easily wipe out an entire tray in a single night. Mulching with fresh sawdust has helped me a lot with this. There are many people out there with lots of strategies for dealing with slugs. 

    Mulberry seedlings often grow very fast. It is almost impossible to stay ahead of them by increasing pot sizes. Trees grown bare root, always have better root systems and are much bigger. One to Three feet is a typical size for first year mulberries, second year trees can be 6ft with beefy roots and thick stems.

    Grafting: Grafting has been one way that works for cloning superior female varieties. Mulberries are a little more difficult than apples or pears, but certainly doable. Bench grafting mulberries in May has worked somewhat well for me. I have had about 60% take. The real struggle has been overwintering grafted mulberries.

The graft unions on mulberry are tender. They need to be protected for their first year or two in my climate (zone 5). Burying the graft union is sometimes enough, but often not enough. The most reliable way to over winter them is to place them in an unheated basement or attached garage.

        If you have never grafted before, I think it is a good idea to practice. You can make grafting cuts on any freshly growing shoots of a nearby tree or bush. Save your valuable plant material for when you feel confident. 

    Layering: I have not had a practical way to layer mulberries because the branches of the trees I have are too high off the ground. I believe air layering could work, but I have not tried it. This could be a good method for someone looking to just propagate a few trees.

    Growing your own mulberries from seed or through cloning is very satisfying and rewarding. Trees can begin bearing fruit at a young age and continue to do so for the rest of your life. Mulberries are a gift to yourself, your kids and grandkids, song birds, wildlife, livestock, and the world in general. There really are very few trees that can match the generosity of a mulberry. So, plant lots of them, the world is only better for their presence.

If you liked this article, check out my book Trees of Power.