Other goods taken include barbecues, Christmas lights, wheelbarrows and bird tables.
Staff have shown video footage of the second incident, which took place between midnight and 1am on Thursday, November 10, to the police.
Owner Richard Allison said: "They cleaned us out of artificial Christmas trees and we are trying to track down extra stock. We have taken extra security precautions as a result of these incidents."
A 32-year-old male from Merseyside has been arrested in relation to the second incident and released on bail pending forensic enquiries.
Any further information please contact PC 3708 Lievers on 0845 1 25 35 45 or Crimestoppers on 0845 555 111.