Learn Spanish (Latin America): Regando poco la orquídea, ves el tallo crecer. - Watering the orchid little, you see the stem grow.

At this level, you will see the gerund used to express a condition, acting as a shortcut for an 'if' clause. Here, regando poco la orquídea means the same thing as si riegas poco la orquídea (if you water the orchid a little). It tells you that the second action (seeing the stem grow) depends entirely on the first.

Why do we use the infinitive crecer at the end instead of a conjugated verb?

With verbs of perception like ver (to see), oír (to hear), and sentir (to feel), you can use an infinitive directly to describe the action being observed. So ves el tallo crecer translates smoothly to 'you see the stem grow.' You could also say ves que el tallo crece, but using the infinitive is very common and natural here.

Could I put poco at the end of the phrase, like regando la orquídea poco?

It is much more natural to keep the adverb poco directly next to the verb it modifies (regando). In Spanish, adverbs usually stay as close as possible to their verbs to make the relationship instantly clear.

Since regando does not have a subject attached, how do we know who is watering the orchid?