Answer: intercalary

AnswerCrossword Clue
intercalary(of a day or a month) Inserted in the calendar to harmonize it with the solar year, e.g., February 29 in leap years
intercalary(of the meristem of a plant) Located between its daughter cells, esp. (in a grass) at or near the base of a leaf
intercalaryinserted in a calendar (for example, a day or a month) also INTERCALAR
intercalaryOf the nature of an insertion