Female not receptive to breeding

Question
I have a female that is 2 1/2 years old, she is in heat and the bleeding has stopped about 6-7 days ago.  I have tried to let the male mount her, but she is not happy and is growling at him.  Is she just not ready?  The male is trying to mount her and is following her where ever she goes. What can I do to know when it will be ok to let him breed or should I just keep letting him try until she lets him mount her and breed?  I have read some of previous questions, can you fill me in on the "flagging" the females does?  What is that exactly?

Answer
Hi Tami:

The female's heat cycle begins with the swelling of the vulva & a bright red discharge. The next portion of the cycle, which on average begins around day 9 or 10 from the initial onset, is the estrus or fertile portion of the cycle. It is only at this point in the cycle when a female will allow & even encourage mating. At this point the discharge will be lighter in flow & color, becoming more of a pinkish to straw color. The estrus portion generally lasts anywhere from 5 to 12 days. Flagging is characterized by the female standing with her rear toward the male & she slowly flicks/wags her tail from side to side -- it's essentially doggy-language for "come hither!" It's simply one of the main signs of her readiness & willingness to mate. Depending on when her cycle first began, you'll have to judge where she is now -- unfortunately all dogs vary somewhat in their cycles so I can only give you averages. The best indicators will be your male's response to her scent & her willingness. If she's never been bred before, there's a possibility that at her age she may be unwilling to accept breeding even if she is in estrus. If this is the case, you'll probably have to restrain her to allow him to mount & penetrate her. I would caution you, though that if she does have this attitude it's also possible, though not definite, that she may reject her puppies once they arrive. This would leave you to mother the litter & that's an extremely difficult job even for a seasoned professional. Also there are many things that can go awry in a pregnancy & whelping, such as over-sized puppies which may require a C-section to deliver, fetal death, stillborn puppies, puppies that for an unknown reason simply fail to thrive, etc. I believe anyone planning to breed should be aware of ALL the risks possible. Breeding doesn't always have a happy ending. Even in the best scenarios you'll encounter many sleepless nights, expensive veterinary bills and more work than you think. I'm not trying to put a damper on your plans but as I stated, I believe you should be aware of all potential problems.
One other thought is if you still have difficulty with her accepting him you can have your vet examine her to see if she's in estrus or at least what stage of heat she is in. I'm including a few links you can read which may vary some in content but may also better help you to understand what's needed for your particular situation. I hope this helps!

http://www.wonderpuppy.net/breeding.htm

http://www.learntobreed.com/

http://lowchensaustralia.com/breeding.htm

http://www.woodhavenlabs.com/dogbreeding.html

http://www.seefido.com/dog-breeding/html/estrus.htm