So you thought a blackberry was always a blackberry, huh? Well, no. Or rather, there are a few different kinds of blackberry, so you have to look close.
I wrote about the invasive Himalayan blackberry a few weeks ago–but now the native Pacific blackberries (Rubus ursinus) are beginning to ripen, so keep your eyes out for them as well. Superficially, these look similar to their invasive cousins. Both grow in prickly mounds of briars. Both have leaves that generally are in groups of three, and many-segmented berries. But Pacific blackberries are all-around more delicate: their berries and their thorns are both more delicate, and their leaves are a lighter green and a thinner texture. Flip one over, and the Pacific’s leaf will be green below while the Himalayan’s leaf will be white.
If you get a look at the flowers, the distinction gets even easier. Pacific blackberry is the only local member of the Rubus genus to have gender-segregated flowers. What this means is that instead of male stamens and female pistils being in the same bloom, some flowers only pack pistils while others only sport stamens.
And that is why botany is awesome. 
Flowers Of Marin 