Six weeks ago she gave birth to their 10th child, Truleigh, who joined five brothers and four sisters aged between 16 and 2.
The Jacksons live in a six-bedroom home in Hamilton and go through 25 loaves of bread, a tray of eggs and about 30 toilet rolls each week.
Their grocery bill is around $500 a week and they receive no financial assistance from the Government, Melanie said.
"My husband is working and building a business so it is not unlike him to get up 4am to do invoicing, then go to work at 6am, come home at 6pm and help with the kids."
The energetic parents have never had a nanny. However, she said, the older kids pitched in with chores, making school lunches and dressing the little ones.
Having a large family, however, does come with people staring, criticism and misconceptions.
"We get asked if we take them on holidays - of course, we do.
"Truleigh was in the frontpack on her first bush walk when she was just two weeks old."
She said they often joined their best friends, who have eight children and one on the way, for picnics.
"I'm sure we look a sight when we pull up at a park with 18 children."