There are 4 optional Wild cards, in addition to 48 Flower cards. (Wild cards fall into Plain cards group) 3 of them are Double cards. The 4th one is a blank card which you can customize to your liking; i) Another Double card, ii) Triple card or iii) anything you want, get creative! There is no need to use all 4 cards, as 2-3 will make the rounds dynamic enough. For a traditional battle of the wits, stick with just the 48 Flower cards.
Wild card(s) from 7 Hand cards
At the beginning of a round, if there is a Wild card(s) among the 7 Hand cards, put it down directly into your Collection square, (It's your bonus card!) and draw the top card of the Flip pile to make 7 Hand cards again.
* Note: In case you fail to do so within the 1st turn, you put it down into the middle of the Flip pile instead, and draw the top card of the Flip pile to add to your Hand cards
Wild card(s) from 6 Ground cards
At the beginning of a round, if there is a Wild card(s) among the 6 Ground cards, the 1st player, the dealer, gets it directly into his/her Collection square and flips the top card of the Flip pile onto the ground to make 6 Ground cards again.
Wild card(s) from the Flip pile
When you complete your set of action on each turn, if the flipped card id a Wild card, you put it directly into your Collection square and flip one more card from the Flip pile to match the ground. But, if the flipped Wild card is in between 3 cards of a month by your play, it gets Trapped together with those 3 cards of a month.