Hey, quick question, gardeners,

I just got into gardening and I'm starting to get into the expensive tier seeds so I don't want to mess things up.

I know seeds cross with whatever is planted adjacent to them, so my question is - when my full garden is harvest-able, can I harvest a plant and plant a seed that will cross with the (also harvest-able) plants adjacent to them?

In other words, when a plant is harvest-able, does it still influence crosses next to it?