I wonder if anyone can help. I have been trying to find out how old Border Terriers are when they become fully grown. The only information I have got is their height and weight when they are adults but not when this is. Poppy is 5 months now and has grown a lot but I don't know how much more she will grow. I would also like to know if she has to be fully grown before she can be spayed. I'd be grateful for any replies.

Hi Sue.
Borders are usually fully grown height wise by about 9 mths, they mature mentally by about 18mths - 2yrs. Some may disagree, I am basing it on mine and those I know. As long as she has had a season and is well in herself, there really isn't a right or wrong age to get her speyed, mid way between seasons is best.
Dawn.