In order to breed green mums, first you will need to breed reddish seed mums with yellow seed mums. Because of Animal Crossing Items this you'll acquire fresh yellow mums with red DNA.

Separate the new hybrid mums and strain them together to create the special purple mums. These mums are going to have the red and yellow DNA.

Independent the new hybrid mums and strain them together to make green.

Be sure that the purple mums are out of Yellow (Hybrid) and not from White mums... I made the mistake of mixing my Purple mums from the sources and had to redo, but once you got the correct purple you can get Green quite fast (also feasible to breed directly from Hybrid yellow).

For Blue Rose I followed the simple 4-step method (maybe not the 9-step which looked way too complex ) and it took about 6 weeks for the first one that I then cloned.... Haven't gotten any more out of my first 4-step flower beds however, the cloned ones are repeating fairly fast. (I had to redo the rose method as I previously followed some erroneous breeding chart)

Keep at it you'll get them!

My green mums came by accident before I started breeding but I haven't been able to get a damn orange hyacinth to spare my life!

Diagonal should do the job also! They simply have to be touching:-RRB- try isolating each set to make sure two reds or 2 yellows are not accidentally breeding.

Roses were my native flower, therefore I went completely ham on them lol

I am only a blue rose away. I'm just awaiting my pink and yellow combos to produce a red and then clone it cheap Animal Crossing Bells and wait patiently for that sweet sweet 1% chance. I'm intentionally not performing any method that needs testing.