kultivi

No suffix in here, whatever it looks like. Kultivi ends in a shape that invites a parse: kulto is a real Esperanto word, and the eye offers kult- plus some -iv- in the middle. There is an -iv- suffix, but it is unofficial and technical: it is not in the Fundamento, it is not in the official list, it lives in words like kreiva and produktiva (see the unofficial affixes), and it is not what you are looking at here. The handful of words that seem to show one (aktiva, pozitiva, motivo) are single borrowed roots wearing Latin grammar that stopped working centuries ago. Kultiv- is one root. The only genuine seam is the -i on the end, which is just the infinitive.

The relatives are real even though the seam is not. Latin colere meant to till a field, and then to tend anything, and then to worship, which is why kulturo, kulto and kolonio are cousins of kultivi rather than derivations of it. Esperanto imported them separately, each already finished, so you cannot get from one to another by adding pieces. This is the ordinary condition of the international vocabulary and it is worth naming: the affix system is genuinely productive, but it does not reach inside a borrowed root and rearrange it.

Growing things, and growing things figuratively. Kultivi is transitive and takes what you tend: kultivi grenon, kultivi rozojn, kultivi la teron. The intransitive partner is kreski, which is what the plant does while you cultivate it, and the two are not interchangeable. Kultivado is cultivation, kultivebla arable, kultivisto a grower. The figurative use carries over exactly as in English: you can kultivi amikecon, kultivi talenton, or kultivi malbonan kutimon, and nobody will hear a field.