Can you solve this little murder mystery?

A whodunnit (for "Who's done it?") is a complex variety of the detective story in which the puzzle is the main feature of interest. The reader is provided with clues from which the identity of the perpetrator of the crime may be deduced before the solution is revealed in the final pages of the book. The investigation is usually conducted by an eccentric amateur or semi-professional detective.

- Clearly somebody in this room murdered Lord Smythe, who, at precisely 3:34 this afternoon, was brutally bludgeoned to death with a blunt instrument. I want each of you to tell me your whereabouts at precisely the time that this dastardly deed took place.
- I was polishing the brass in the master bedroom.
- I was buttering His Lordship’s scones below stairs, sir.
- I was planting my petunias in the potting shed.
- Constable, arrest Lady Smythe!
- Oh, but- how did you know?
- Madam, as any horticulturist will tell you, one does not plant petunias until May is out. Take her away.
It’s just a matter of observation. The real question is how observant were you?

BLUDGEONED= A short heavy club, usually of wood, that is thicker or loaded at one end.

BLUNT= not sharp.

YOUR WHEREABOUTS: the place where you were, your location

DASTARDLY = Cowardly and malicious

DEED= action, event

POLISHING= to polish is to rub an object to make it look shiny

THE BRASS= the objects in a house (usually for decoration) made of an yellowish alloy of copper and zinc (see picture)

SCONE= a thin, flat cake (see picture)

POTTING SHED= a building in which plants are set in flowerpots and in which empty pots, potting compost, etc., are stored. A greenhouse. (see picture)

HORTICULTURIST= one who cultivates flowers and other plants

UNTIL MAY IS OUT= until the month of May finishes.