The short answer: they come from the same plant. Both Jamaican black castor oil and regular castor oil are pressed from the seeds of Ricinus communis. The difference is how they are processed, not the species.
Regular castor oil is cold-pressed and usually clear to pale yellow. Jamaican black castor oil is made by roasting the beans first, then pressing them and adding the leftover ash. That roasting is where the dark color, the smoky scent, and the more alkaline pH come from.
What the processing actually changes
The ash content gives JBCO a slightly higher pH, which some people find helps lift the hair cuticle and clear scalp buildup. Others with sensitive skin find that same alkalinity irritating.
Nutritionally, both oils are roughly 90 percent ricinoleic acid, the fatty acid credited with most castor oil claims. Roasting does not add nutrients. If anything, high heat can degrade a small fraction of them. So the reputation for being more potent is more about texture and feel than a richer nutrient profile.
Which one suits your hair
Thick, coily, or dry hair often takes well to JBCO because the heavier feel and buildup-clearing reputation match that texture. Fine or chemically sensitive hair usually does better with plain cold-pressed castor oil, which is gentler and lower in pH.
Neither oil is a proven hair-growth treatment on its own. If growth is your goal, technique matters more than which bottle you buy. Our guide on castor oil for hair growth breaks down what the evidence supports.
If you are choosing between castor and other ancestral oils, the comparison in batana oil vs castor oil is a useful next read. And whichever oil you land on, applying it well beats using more of it, which is why the steps in how to apply batana oil carry over directly.
How to test the difference yourself
Buy small sizes of each. Use one on your scalp and lengths for two weeks, then switch. Track how your scalp feels, how fast the oil absorbs, and whether the smell bothers you. Your own scalp is the only fair judge here.