Bainbridge said that the plant thefts make a noticeable impact on the collection, with conservatory plants in particular, such as orchids and other foliage plants, including baskets, being targeted.
"The orchids only flower once a year and a lot of care goes into them to ensure they will flower, so when they're stolen it's hugely disheartening for the contractors who look after them and disappointing for the general public who come out to admire the displays.
"Outdoor plants are also a frequent target with people pulling established plants out of the ground, often damaging them to the point where they potentially will not survive anyway.
"A lot of care and attention goes into providing these facilities and producing these beautiful displays and we want to make sure visiting the public gardens is an experience everyone can continue to enjoy."
Anyone with information surrounding the thefts is encouraged to contact Whanganui Police.