Foraging Fun: Mulberries

The white mulberry (Morus alba) is probably one of the the top 5 most common urban weed trees (particularly in the Greater Toronto Area and likely beyond) and if you live almost anywhere in a large town or city in eastern North America if not elsewhere on the continent, you’ve probably identified this species not necessarily by name but by it’s impact on the surrounding environment. Frequent patches of dark purple/almost black stains on pavement that can be seen when driving/biking along roads or walking down sidewalks and passing driveways in late June through to mid August are all sure signs that there are white mulberry trees growing bountifully in your area. Unfortunately, the most common interaction that people have with the white mulberry is as an almost invincible weed or as that tree that voluntarily colors your driveway every summer and not a bountiful and reliable producer of delicious and nutritious fruit, which is the perspective that I prefer to uphold and advocate for.

Despite the mention of the ‘mulberry bush’ in the familiar children’s nursery rhyme, most if not all true mulberries (in the genus Morus) are actually fairly large trees when mature, and it does not take them long to become mature specimens. Especially of the white mulberry, growth when young is rapid and fierce, sometimes adding at least a couple meters of length or height each year. The trees also have an uncanny disposition for seemingly favoring the most inhospitable of living conditions, readily germinating and flourishing in alleyways, edges of parking lots, along fences, in abandoned stairwells and generally anywhere where there is even a minute amount of soil and no one weeds them out on sight. If left to establish themselves, which can only take a few years from seed, mulberry trees are tirelessly aggressive and will sucker like there’s no tomorrow even after years of attack with pruning shears, saws and herbicides from dedicated and equally aggravated property owners and gardeners. It’s not a good idea to rub a mulberry the wrong way, you can almost hear them start to grow after you hack them back.

Mature trees tend to have more regularly shaped and glossier leaves than younger trees or individuals that aren't growing in full sun.
Mature trees tend to have more regularly shaped and glossier leaves, while young trees or those growing in partly shady conditions may have highly variably and rough textured leaves.

Of course, white mulberries will also do extremely well in rich, moist garden soil if they have the chance. If growing in a fertile sunny and well-watered environment they can live for at least a hundred years and become massive and – dare I say handsome – shade trees that are a pleasure to have in the yard that add character and charm that’s all their own. But other than the deep purple-staining berries, how does one identify a white mulberry tree? The leaves grow alternately and are highly variable in shape and size but are generally cordate (heart shaped) with serrated leaf margins and a pointed tip, although sometimes (especially vigorously growing young trees) the leaves are also cut with deeply rounded irregular lobes.

The white mulberry is not the only species of mulberry and like many weedy urban trees is a non-native species. The red mulberry (M. rubra) is native to eastern North America, including southern Ontario, but it is a critically endangered species in Canada that only existed in a few sites scattered along the southern half of the Niagara Escarpment. The red mulberry is at risk of genetic dilution through hybridization with white mulberries, a problem that is nearly impossible to control and may eventually put the genetic purity of the American red mulberry in jeopardy. Another species, the black mulberry (M. nigra) is native to Eurasia, and is similar in many respects to M. rubra. Both M. rubra and M. nigra are said to have very sweet and flavorful berries while the white mulberry has comparatively bland tasting fruits even when they are at their best. This seems unfortunate that the least delicious of the species were to become naturalized close to home, but beggars can’t be choosers, nor can foragers by picky eaters.

I find white mulberries to be a summer specialty. The berries are relatively easy to collect, and very ripe berries often drop from the branches with the slightest touch. Not all the berries on the trees ripen simultaneously, which stretches the season out to around 3-4weeks at times for an individual tree and prevents single seed distributors from stripping the entire tree at once. If possible (and with care of course) it is sometimes is easier and faster to simply grab a hold of a branch and shake it over a clean tarp of blanket to collect the fruit. Hand picking is highly enjoyable though and no matter how careful one is they will find their hands and fingertips stained purple at the end of a visit to a mulberry tree. Hard and green immature fruit is actually highly laxative, slightly toxic and inconsistently hallucinogenic when unripe, which is not a combination of qualities that you want to subject yourself to.

A basket of freshly harvested mulberries from a local park. Finding trees which bear the heaviest or best tasting berries requires a lot time and effort spent searching for these these among other food resources in your local environment.

Fresh mulberries are delicate and so can get crushed under their own weight in baskets or bags, so care is needed when collecting so that one does not come home to pulp and juice instead of berries. They do not last long past a couple days at room temperature or more than a week in the fridge and turn into a tasteless mush that easily spoils if thawed from frozen. This makes canning and preserving the mulberries as jam or chutney your best bet for actually enjoying them out of season. They’re great on their own or mixed with sweeter fruits for canning or cooked into sauce, added to pies, baked goods, deserts, granola or smoothies.

Interestingly enough the white mulberry is indigenous to east and southern Asia, where it is was (and is still used) in the production of silkworms. Silkworms eat mulberry leaves and so both the trees and the silkworms were imported from Asia in the 19th century to start up a North American silk trade that would hopefully have competed with the well established market that already existed overseas. Despite those with good intentions, the program failed miserably. As breeding plots and test locations were abandoned the mulberry trees that were grown to feed the worms inevitably started to bear fruit. These were then obligingly cleaned up by birds who deposited the seeds a great distance away. I find it very interesting to observe that after serving it’s intended purpose in the silk trade, the tree did not simply fade into the background but has made itself quite at home in the same habitat that we seem to enjoy crafting for ourselves.

With mulberry trees so abundant in some areas, it seems like such a waste to see the berries being produced by the pailful from even fairly small and immature trees going unused. Mulberries are rich in vitamin C, Vitamin B-12, vitamin k, iron and certain antioxidant and polyphenols which discourage certain neurological diseases and chronic inflammation among many other physiological benefits. Mulberries are one of the best examples of an undiscovered and under valued ‘accidental’ resource, and I believe if we can claim ourselves to be intelligent and creative than ought to seize this wonderful opportunity to feed and nourish communities with virtually no negative or degrative effect on the environment whatsoever. Few know of the riches that drop to the ground each summer, probably translatable to hundreds if not thousands of dollars worth of potentially marketable fruit.