When people say that they have a "Mother plant" in their grow/grow room, they are referring to a large female plant that is in a constant state of vegetation.
What is special about it is, usually you pick your
favorite plant, from your favorite strain to be you mother plant (once
you have seen how fast/tall it grows, or if you've seen it's mother
grow), and you make a clone. That clone will be the mother plant, and
all your other plants can go into flower, get harvested and be gone.
what the mother plant allows you to do, is make clones of not just any
plant, but your favorite plant. And a guaranteed female, since you
You just keep the "Mother plant" in veg, and clone it
whenever you want. (I'll make a thread on cloning next grow I visit, or
of my own, I need pictures or video for that).
Mother plants can get
very big, and you might even want to just keep a mother plant through 2
or 3 grows, then make a new one, and see what she flowers into after all
that veg time :D If you give her a big enough bucket, it'll be
something beautiful, and huge :D