Genus: Rubus
Rubus is a handy genus to know, and an easy one to ID – at least to the genus level. The plant has long woody canes that either trail or mound together to form thickets. The canes are (usually) thorny. leaves are palmately compound, with 3-7 leaflets per leaf. The fruits are aggregates of a bunch of drupelets – and are edible. Common names include blackberry, raspberry, and many hybrids (including logan, boysen, marion, salmon, thimble, and dew berries). All you really need for the genus ID is the aggregate drupelet fruit (which means that each little ball in the aggregate fruit is actually a little fruit of it’s own, with the fleshy covering and the seed inside), and the canes. Other aggregate drupelets you’re likely to find are mulberries, but those grow on bushes or trees, not on canes or vines. (Not that it matters for edibility, because mulberries are edible too.)
In Northern California, Rubus species are very widespread. Roadsides, riversides, and trailsides are covered with them. They root from their cane bases, and also root where the canes touch soil, spread via rhizomes, and they also produce a bunch of seeds in every aggregate fruit.
Species: Rubus spp.
It is relatively easy to tell a blackberry from a raspberry. First, by their color – blackberries are usually dark purple or black, raspberries often red. Second, by their core. When you pluck a ripe berry, raspberries are hollow, and blackberries are not.
After you’ve narrowed it down to blackberries, getting to the species level is more difficult (there are over 1,350) in the genus. We’ll simplify by going hyper-local. In California we really only have 4 species of blackberry that you’re likely to encounter in the wild (there are more, but they appear to be quite rare). In order of prevalence, these species are:
Rubus bifrons (Armenian or Himalayan blackberry) – these may or may not be different species, depending on who you ask. The taxonomy is confused here, and there are several species names are collectively gathered (possibly temporarily) under R. bifrons: R. armeniacus, procerus, discolor are all currently treated as synonyms. Non-native and rated as invasive by Cal-IPC.
Rubus ursinus (Trailing blackberry), a CA native
Rubus laciniatus (Cutleaf blackberry), non-native, but not rated as invasive
Rubus ulmifolius (Elmleaf blackberry), non-native, but not rated as invasive
Partial Descriptions:
R. laciniatus: Leaves: R. laciniatus has very distinctive leaves. As the common name suggests, the leaves are deeply incised. Some of the incisions go half way or more to the midrib. This is unique and sufficient to ID R. laciniatus.
R. bifrons: Leaves: leaflets are oval or elliptical with a rounded base and pointed tip. They are unlobed, serrated, and usually have 3-5 leaflets. Stems: R. bifrons has large stout thorns, and the whitish pruinose coating is absent or light.
R. ursinus: Leaves: leaflets are generally wider at the base than at the tip, sometimes much wider. They also have a more variable margin, sometimes looking almost lobed with serrated margins. The compound leaves usually have 3 leaflets (but may have 5). Stems: thin thorns, often hairy, usually strongly pruinose (has a whitish coating that easily wipes off – like a prune).
R. ulmifolius: Leaves: leaflets longer than they are wide, with rounded or wedge shaped bases, may have nearly parallel sides, and a pointed tip. They are unlobed and serrated. The compound leaves usually have 3-5 leaflets. Stems: Thorns may be absent. If thorns are present, they are thin but have a broad base. Stems are often hairy, and are strongly pruinose.
Key features:
- Trailing or mounding canes
- Palmately compound leaves with serrated margins
- Dark purple to black aggregate fruit with a solid core (not hollow when ripe fruit is plucked)
- Deeply incised leaves: R. lacinatus
- Large strong thorns: R. bifrons
- No thorns: R. ulmifolius
- Leaves wider at base than tip, may be lobed, frequently 3 leaflets: R. ursinus
- Leaves longer than wide, often nearly parallel sides, unlobed, usually 5 leaflets: R. ulmifolius
Frequently confused species:
A common confusion that I see on the various plant forums I read is between Rubus spp. and Poison Oak (Toxicodendron diversilobum). While poison oak does have palmately compound leaves, and can have a thickety or viny habit, there are some key differences.
- Thorns: Poison oak doesn’t have thorns on its stems or leaves. Even if a Rubus doesn’t have thorns on its stem, it will on the underside of its leaf.
- Leaf margins: Rubus are serrated, Poison Oak is scalloped, lobed or entire.
- Leaf tips: Rubus are pointed, Poison Oak is rounded.
- Number of leaflets: Poison Oak usually has 3, Rubus usually has 5 or more.
- Fruit: I think if fruit are present, the confusion goes away – the aggregate druplets of Rubus spp. are distinctive.
Links:
- Here’s my observation in iNaturalist.
- And here’s my YouTube short.
Sources:
My sources are a combination of: Flora of North America, Jepson eflora, Calflora, iNaturalist and Wikipedia.
Why so limited?
There are a lot (a really really lot) more that you could say about these plants. I could describe their flowers, fruit, reproductive cycles, even chromosome count among a million more details. I intentionally try to distill the information available on the plants I identify to things that are persistent, observable, easy to understand, local, and relevant. (For more info, see this post.)
Help Us Learn:
First, as it says all over my brand, I’m a totally self-taught beginner naturalist… so please, consult other sources for definitive identification.
Second, if I got anything wrong, please help me and the rest of the interweb out by commenting and let me know! I am completely self-taught and a hobbyist, but I do try to be diligent in my research (so please be gentle). I would love any feedback on corrections, key features I missed, interesting tidbits, and uses for the plant (both how it’s useful to nature and it’s environment – or not – and how it’s uses by people).
