How Does Indian-Plum Have Sex?
What does Indian-plum have in common with Cannabis? They both are dioecious plants, meaning they have separate male and female plants. Plant specialist Jerad Bryant breaks down how to identify whether this shrub is male or female, and how this plant has sex.
An Oemleria cerasiformis shrub blooms bell-shaped flowers in early spring.
Indian-plum, Oemleria cerasiformis, is a suckering shrub native to the Pacific Northwest and parts of northern California. Because it is native to these regions, it performs extremely well in various ecosystems. Find it growing underneath Populous trichocarpa near riverbanks and in shaded forests with moist, wet soil.
At first glance, this shrub may seem like any other. It has multiple branches sprouting from a central area, it is deciduous, and it spreads readily in the right environments. Take a closer look and you’ll see why this shrub stuns onlookers each spring. It is one of the first plants to break buds with clusters of white bell-shaped flowers and shiny green foliage. When it blooms, it emits a delightfully floral scent akin to flowering plum and cherry trees.
The main reason this plant is unique is the way it reproduces. It’s unlike a tomato, where both male and female parts grow in the same flowers on one plant. Indian-plum is also different than monoecious plants like those in the Alnus and Corylus genera, where one plant has separate male and female flowers on the same plant. This native is dioecious, meaning each Oemleria shrub is female or male. Read on to discover how this plant has sex, and how male and female plants can be evolutionarily advantageous for the species.
Monoecy vs. Dioecy
So, what is dioecy? Well, dioecy is a type of sexual reproduction in plants where a male plant has male flowers and a female plant has female flowers. To successfully reproduce, a male and a female shrub must exchange pollen and ovules with one other. Pollen has to travel from the male flowers on one plant into the female flowers on another. The Cannabis, Cycas, and Silene genera are other examples of dioecious plants.
Dioecy may seem more difficult than monoecy, as successful sexual reproduction requires two specimens rather than one. For a while, it was believed dioecy is an evolutionary “dead-end” and not a feasible evolutionary advantage. Recent studies are proving otherwise. A study published in the ‘Molecular Biology and Evolution’ journal shows that dioecy promotes increased genetic diversity. This could lead to beneficial mutations in a changing world.
Why would dioecy help increase genetic diversity in a population? Because Oemleria plants require two separate specimens to reproduce, the offspring will have a new mix of genetic material each year. Rather than one shrub using its pollen to create seeds, Indian-plum only reproduces by mixing pollen and ovules from two separate shrubs. This creates new offspring with unique genetic combinations. In a rapidly changing climate, this may prove beneficial for Indian-plum.
How to Identify Indian-Plum
Use a few different characteristics to successfully identify an Oemleria cerasiformis shrub. Regardless of their gender, all shrubs of this species have spear-shaped leaves that are forest-green on top and grayish underneath with little fuzzy hairs. This plant releases a strong, oily fragrance when you crush the leaves. The flowers are fragrant, and they smell sweeter than the crushed foliage.
Male Oemleria shrubs bloom profusely.
Oemleria bark is brown, gray, and has raised bumps.
After the plants have fully leafed out in late spring, they lack the flowers that make identification easy. Female plants grow light pink fruits that swell and turn dark blue. The fruits are edible, although they are slightly bitter and contain large pits. The name “Indian-plum” is fitting, as the small fruits on these plants resemble small plums when fully grown.
If there are no flowers or fruits on the shrub, look at its form, habitat, and structure. Indian plum shrubs have multiple stems from a central point. They grow up and arch over, with mature plants’ branches reaching over ten feet tall. In woodland and meadow settings, this shrub spreads out and colonizes the area. I have seen populations of over thirty plants growing together. In the early spring, these large clusters of Indian-plums are stunning sights to see, with white blooms spanning the entire forest.
Are there differences between the male and female flowers on Indian-plum, or do they look the same? Let’s break it down.
Male Indian-Plum
Male O. cerasiformis flowers have many anthers and no stigmas.
You can tell the difference between male and female Oemleria when they are in full bloom. Male plants have clusters of male flowers filled with stamens. Pollen holders, called anthers, hang on to the end of the stamens. They dangle out the flower in hopes of spreading their genetic material.
Male plants will also have more clusters of flowers than female plants. In the population growing near me by the Willamette River, the male plants all have three to five times as many bloom clusters as the female plants. Why is this?
A study in the 1980s found that male Oemleria plants had higher rates of annual flowering than females over time. In most dioecious species, it seems that setting fruit is a high-resource investment—female plants thus have fewer flowers because they can only create a finite amount of fruit. The plants in my local ecosystem reflect this trend.
Female Indian-Plum
Female O. cerasiformis flowers have stigmas attached to styles.
The only way an Oemleria population can live is if female Oemleria plants are in the area. Female shrubs set seed inside plum-colored fruit. Their flowers contain a few stigmas attached to styles. The styles go deep into the flower and connect to the ovaries; inside the ovaries, ovules exist and await pollination from pollen. Once pollen falls inside a stigma, goes down into the style, and incepts the ovule, pollination is successful.
Female Indian-plum shrubs have fewer flowers on average each year than male plants. Making seeds is a resource-intensive process, and fewer flowers means fewer investments. These few investments pay off when the shrubs grow pink fruits that mature to a plum color. Birds love them, and we humans can eat them too.
Fun Facts
I read in a native plant book that Oemleria cerasiformis leaves taste like cucumbers. I thought, “No way!”
After trying leaves off the shrubs in my local area, I can confirm they taste like cucumbers! After the cucumber flavor, the leaves are a bit bitter, but it is a fun way to identify the plant nonetheless. As always, be sure what you eat is what you intend to eat, and never consume plants you don’t recognize.
Several First Nation groups like the Squamish, Straits Salish, and Halq’emeylem ate small quantities of the berries. They ate them fresh off the plant and prepared them into dried fruits and fruit dishes. Large quantities of the berries may upset some people’s stomachs, so be sure not to overindulge if you’ve never had them. Slow exposure over time is best to see if your tummy can tolerate the fruit.
Conclusion
My favorite part of Indian-plum? I love that in early spring they are one of the first blooming shrubs. I love that they smell sweet when blooming, and that their leaves taste like cucumbers. I also love that they grow edible fruit, and are native to the Pacific Northwest. What else is there to love?
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