Memories are thought to be so fundamentally cognitive that some theorists argue that they’re a marker of whether an organism can do the most basic kinds of thinking. Surely memory requires a brain?
"What does it even mean to say that a mallow can learn and remember the location of the sunrise? The idea that plants can behave intelligently, let alone learn or form memories, was a fringe notion until quite recently.
However, over the past decade or so this view has been forcefully challenged. The mallow isn’t an anomaly. Plants are not simply organic, passive automata. We now know that they can sense and integrate information about dozens of different environmental variables, and that they use this knowledge to guide flexible, adaptive behaviour."
Excerpt from a great article from Aeon which you can read HERE.
See also After Nature posts "Can plants really communicate with each other?"; "Some thoughts on a phenomenology of vegetal life"; and "Mathew David Segall, media ecology, and biosemiotics."