Call them what you will...Watercolour paint will spread and do it's own thing if you are not careful.
Some call them 'blooms' others refer to them as 'cauliflowers'.
Okay, I've already done a blog post on this, but since it is a recurring issue with artists, especially those first learning, I felt it was worth another post here.
In this example painting of a Lighthouse, you'll notice that there is a darker area representing a window on the body of the building. I did this
Whilst the other paint was WET, and yet it didn't spread > bloom > cauliflower.
This was possible because when I added the window, I used a
thicker consistency of paint, thus the
weight of the paint being added was
heavier than the paint it was going into, and hence it didn't spread.
~ I hope this blog post is of help ~