Horticulture Specimens

As clued by the top text of grafting a single piece into each plant, each drawing and text gives a clue to an answer that is a plant genus with an extra letter.

ex. the stick man with a crossed out speech bubble clues the answer SILENCE, which is the plant genus SILENE with an additional C

Drawing	Genus	Extra
SILENCE	SILENE	C
PI PEAR	PIPER	A
POLLY GALA	POLYGALA	L
PSYCHO TRIAL	PSYCHOTRIA	L
PANDA UNUS	PANDANUS	U
CAN REX	CAREX	N
PANIC UMA	PANICUM	A

This spells the phrase CALLUNA with the extra letters, which is a plant whose common name is HEATHER