A Slightly Obsessive Guide to Raspberry Identification
If you came to this page for an easy answer for identifying the raspberries in your neighborhood, you may want to turn around. Raspberries present botanists with some of the most challenging identification problems in the world. As a layperson, using the simple term ‘raspberry’ is probably enough. But some of us want to dig deeper and discover whether it’s a roadside raspberry or a dwarf raspberry or an arctic raspberry. If you’re looking for a more introductory berry guide, perhaps start here.
The stunning complexity of life on Earth challenges biologists with putting plants and animals into certain groups. In school, we’re taught about species as if they are concrete and certain things. Fortunately or unfortunately, depending on how you look at it, this just isn’t the case.
It turns out species can hybridize species and bacteria can steal genes from animals. This transfer from one kingdom or species to another creates a web of life rather than a tree of life, with different branches intersecting each other over time. No group represents this beautiful complexity more than, you guessed it, raspberries.
Let’s Do the Basic Taxonomy
Botanists typically only use the family, genus, and species to describe plants. ‘Species’ is the most descriptive whereas ‘family’ is more broad and includes many species. All raspberry species are in the genus Rubus, along with some other tasty plants like blackberries and tayberries.
Rubus is in the rose family, which is a very commercially important group of plants. The rose family contains beautiful roses, apples, apricots, peaches, and even almonds! Rubus contains many hundreds of species, which is a bit too big for scientists to work with.
These scientists broke down Rubus into about a dozen subgenera. Raspberries are the Ideobatus subgenus, whereas the closely related blackberries are in the Rubus subgenus (yes, of the Rubus genus). Confused yet? This is just the start of the complex life of a raspberry.
What Characterizes Rubus
The common name for anything in the Rubus genus is bramble. The picture you have in your head is probably about right. These plants usually (you will never catch a botanist saying always) have prickles or thorns, grow on canes, and have berries that are a bunch of tiny berries put together. They have flowers with five petals that range from white to pink. Rubus leaves look like 3-7 smaller leaves, or leaflets, on a single stalk.
Raspberries grow non-fruit bearing canes in the first year. These canes fruit during their second year of growth. After this, that cane dies. While each raspberry cane lives only two years, the rootmass can live for decades. Sometimes you need this first year cane to identify species of raspberries because the edible fruits from the second year can look so similar.
If you see anything in the wild that looks like it belongs to Rubus, it is probably edible. This is a delicious genus with all sorts of wild berries, such as the cloud berry in the arctic which tastes like apple pie!
Gene Overflow – Polyploidy
We humans have genes from our two parents. We inherit parts of our father’s and parts of our mother’s to make each of us unique and individual. Half of our genes come from one side and the other half from the other side. Scientists call humans a diploid species. ‘Di’ means two and ‘ploid’ means chromosomes or genes. Pretty easy, right? We, humans, are pretty simple when it comes to our genes.
When we adventure beyond humans, we find a much more intimidating world of reproduction. Imagine having the genes from four or six or ten parents within you? That’s a little bit like polyploidy. Instead of two sets of genes combining during reproduction, it’s many.
Polyploidy is common in the natural world. In fact, plants in the Rubus genus are almost entirely polyploids. In a study of 750 species of European Rubus, only 3 were diploids like us humans. Many of the raspberries had four sets of chromosomes. If humans had this complexity, it would mean that every trait, such as hair color, height, and foot size would have four sets of genes rather than two.
The differences in these genes account for the variation we see between people. Therefore, if there are twice as many genes themselves, the outcomes are exponentially more variable. In short, polyploidy makes it easier for plants to express different forms of themselves. The same species of raspberry could be short and run along the ground or grow tall and cane-like, depending on the sets of genes mixed together.
Raspberries Can Mate With Themselves and Other Species
As if polyploidy didn’t make the raspberries difficult enough, they can also mate with themselves and with other species of raspberries, blackberries, and other groups in the Rubus genus.
Plants hybridize with each other all the time. The cultivars of raspberries commonly grown as crops are often hybrids between different species of raspberries. Horticulturalists give them fun names, like Kiwi Gold, Honey Queen, Octavia, and Cascade Dawn.
The Olallieberry is a great example of hybridization. It is a hybrid between the youngberry and a loganberry. The loganberry is a hybrid of a European raspberry and a North American raspberry. The youngberry is a multi-generation hybrid of a species of blackberry, raspberry, and tayberry. Essentially, the olallieberry is a mix of everything Rubus has to offer! Unlike many types of food cultivar hybrids, which are variations within the same species, the Olallieberry contains genes from at least five different species.
This hybridization also happens in nature, sometimes between native and non-native Rubus species. Sometimes, these semi-native hybrids are more fit for their environment than either plant was before. This makes the plants more likely to reproduce and colonize more land. This constant mixing of genes and species creates a confusing landscape for taxonomists.
Apomixis – Self Mating
The final complicating factor in raspberry ID is apomixis. That’s really just a fancy word for sexual reproduction with oneself. This means that a raspberry plant can use pollen and the eggs from the same plant to create seeds, which will turn into fertile plants in the future. This ‘selfing,’ combined with the polyploidy we touched on earlier, leads to all sorts of strange combinations. This is different than clonal reproduction, which is more common in the plant world. Apomixis happens in less than 1% of plants but happens in most Rubus.
In Madagascar, scientists documented a non-native raspberry hybridizing with a native raspberry. This plant then spread rapidly through self-mating, because it was able to maintain the beneficial traits from the hybridization. This somewhat alien raspberry then invaded many islands in the Indian Ocean. Is it a native plant, an exotic plant, or a new species? These are the tough questions botanists must deal with when faced with complicated plants, such as Rubus.
To Worry About the Species of Raspberry or Not?
Sometimes it’s best to just eat the berries rather than worry about the correct species of Rubus. It takes a lot of time and effort to figure it out. If you’re going to eat the berries anyway, does it really matter?
If you want to impress your friends or search for a species berry with a particular flavor, maybe it does matter. Perhaps you’re concerned with the conservation of a certain species of Rubus. In that case, proper identification is crucial. However, for most of us, the tasty fruit is enough on its own!