How can i cross pollinate?

Question

and is there any similarities that the two plants have to have?

Answer 1

Use a small, fine, soft paint brush to pick up pollen from one flower and move to the other.  

The plants have to be closely enough related to cross them, so within the same genus at a minimum.  Some plant species will hybridize with others (like black and red spruces).

Answer 2

Cross pollination is the process of taking pollen from one plant and transfering it to another.  The similarity is that the plants need to be the same type:  tomato to tomato, apple to apple, etc.  The only thing that affects this is that the number of chromosomes must be the same for both the male (pollen donator) and the female (pollen acceptor).  For example, some plants like potatoes have 2x and 4x chromosomes.  You cannot just cross a 2x with a 4x.  It is possible with modern technology and a bit of manipulation, but not something you will be doing out in your garden with a tweezers and Q-tip!

Answer 3

Cross-pollination (syngamy): pollen is delivered to a flower of a different plant. Plants adapted to outcross or cross-pollinise have taller stamens than carpels to better spread pollen to other flowers.  Hybridization is effective pollination between flowers of different species of the same genus, or even between flowers of different genera (as in the case of several orchids).