You'll just have to take the bottle and find some more water. From the plant, go u w, n, e, u, e, e, and d to find the nearest water. Then you can fill bottle.

(That water is not very near, is it?)

To get back to the plant, you go u, w, w, d, w, s, s and d. At that point you can water plant once more and then the plant will grow high enough that you can climb plant.

Just for fun, try watering the plant once more.