Tree portrait: Mulberry

Red, white, and somewhere in between

Mulberries ranging from not even close to melt in your mouth

It was a $15 box store plant in a one gallon pot, described on the tag as a self-fertile red mulberry that reached only 6 feet. It seemed too good to be true, and the first year it fruited the berries arrived in fall and had no time to ripen before cold weather. Then this spring it got its act together and covered itself in super sweet drupelets before the end of May.

It's one of those plants one sometimes lucks into unexpectedly, like the tiny $3 hardy banana starts that I found several years ago at the same mega-store. That bit of happenstance started my banana adventure, and the tiny plants have turned into three shady groves of statuesque tropical foliage.

My current assessment of the dwarf mulberry is that it is a perfect food plant for a sunny spot that produces a delicious treat and needs little in return. And yet I've never seen one for sale locally before or since. This is the type of thing that plant breeders should be working on instead of developing seed-free maples and golden-leafed barberries. Though I love my ornamental plants, I admit it's disheartening to think about all the time and resources put into producing plants whose only purpose is to look a certain way and not make a mess.

A male white mulberry creates a shady oasis

My cute little mulberry shrub was developed from the native Morus rubra, or red mulberry tree, which is found in most of the eastern half of the U.S. excluding far northern parts. The invasive white mulberry, native to China, has colonized much of this area also. There are many wild mulberry trees on the property, but it is not clear what exactly what they are. Descriptions of the two species include ways to tell them apart, but end with the admonition that they often hybridize, making positive identification impossible in many cases.

According to most descriptions, red mulberries are tall, stately trees, partial to rich, moist bottomlands. They are not usually pioneer trees, but often appear in gaps in mature forests created when large trees die. Their leaves are in general larger, more hairy, and less shiny that white mulberry. While fruit color varies among individual trees of both species, and is not considered a reliable trait for identification, the taste of the red mulberry is considered superior. White mulberries tend to be bland, and the trees were brought to this country as food for silkworms rather than for human consumption.

Mulberry mess

Fortified with the information of the previous paragraph, I've been attempting to identify the numerous wild-growing individuals distributed across the property. They seem to be white mulberries, though many exhibit confusing traits, indicating we probably have hybrids. While the ideal is a healthy population of native trees, I have no plans for removal of the white mulberries or apparent hybrids except the stray seedlings in the garden, flower beds, and fence lines. Trees in these spots would be removed regardless of type.

This is probably a good place for a quick note on the word invasive. These days the word is often used irresponsibly to refer all sorts of things like bad garden weeds, pioneer species, or merely disliked plants. I use it to mean plants evaluated by the Ohio Department of Agriculture or the Ohio Invasive Plants Council as invasive or potentially so. The state of Ohio defines invasives as “plant species that are not native to this state whose introduction causes or is likely to cause economic or environmental harm or harm to human health as determined by scientific studies.”

At the ODA, a five member advisory committee makes decisions regarding invasives and there are currently 63 plants listed and prohibited for sale in the state with white mulberry being one. I take this classification seriously, and respect the prohibition on sales, but take a pragmatic approach to land management. I work to control unwanted plants of all stripes including exotic and indigenous, and their desirability is usually defined by their current location, not their country of origin. Eradication of white mulberry, like many other invasives that cover the land, would be impossible, and therefore will not be attempted.

A small specimen in the barnyard, with mature tree in background

In my opinion, control of the population beyond garden beds and fence lines isn't necessary because my mulberry trees behave like native plants. By this I mean they are scattered here and there throughout the woods and the population is relatively stable. They don't suddenly enter established forest, disrupting it and crowding out other trees. They don't exhibit the tendency to colonize disturbed areas any more aggressively than box elders, cherries, or sycamores, and in fact are somewhat more shy and retiring than these enthusiastic natives.

The main threat of white mulberries seems to be less physical and more genetic. Simply by their presence and the fact that they interbreed with red mulberries, they threaten the more desirable native species through a process called genetic swamping.

To understand how this works, first consider competing trees that don't interbreed. For example, if your neighbor has a Norway maple, its progeny may invade your woodlot because the seedlings are shade tolerant and can get off to a good start under a closed canopy. Seeds of your native maples succeed only when they get lucky and germinate in a relatively sunny spot. As a result, the Norways become locally more common.

Dwarf red mulberry, now producing

A similar scenario might play out with white and red mulberry trees, but a more insidious trend is also at work as the two tree types hybridize. Red mulberry flowers are pollinated by white mulberries pollen, resulting in seeds of a genetic mix. These seeds sprout and mature, and over time pure red mulberry trees die off and become increasingly rare.

What does this mean for land managers? Knowledge is sometimes power, but this time it counts for very little. As with most invasive species on the property, in this case there is not much I can do. Getting pumped up with outrage and vowing to resort to chemicals is pointless. The processes at work are unstoppable, so it's advised to make the best of them. For me this means keeping mulberries of all sorts out of places where they should not be growing, posssibly adding cultivars like my dwarf tree when it makes sense, and encouraging young trees wherever they might benefit livestock. For those with the wherewithal, a positive step would be purchasing and planting genetically pure red mulberries. I hope to do this in the future when funds permit.

A section of mulberry makes a good garden table

Meanwhile, I've let a few white mulberry trees get started in the chicken areas, simply by mowing around them. One has produced berries for the first time, while the others as yet show no signs of fruiting. Even males are valuable however, because the horses relish the leaves and quickly strip branches bare. If the rest turn out to be males, I'll pollard them regularly and toss the limbs to the equines.

The mulberry is a dioecious species, with male and female flowers borne on separate trees. Most of our trees seem to be males, and — following typical farm luck — the few large female trees here have grown in the most inconvenient spots. In early June, berries rain down on the parking spots, driveway, and barn entrance, and never land inside the chicken fences where foraging hens could benefit from a juicy snack.

Despite the mess, I appreciate our mulberry trees — male, female, red, white, and hybrid. They are a part of the landscape here and will remain so. Fruit for wildlife and humans, supplemental horse fodder, plus shade and firewood, are the gifts they offer, only asking for a little space in return. Making use of these gifts is the best way forward.