The manager of Wellington Botanic Garden says it is likely that exotic plants taken from an indoor garden have been stolen for sale.
A dozen plants were taken from the Begonia House overnight on Monday.
They are a mix of rare and common, and range from small ones to over a metre tall.
Police said they been told about the incident and were assessing the information.
Manager David Sole said the plants were worth thousands of dollars and and there was no signs of a break-in.
He said he thought the theft was linked to a similar one at the Christchurch Botanic Gardens last month, with glasshouses around the country having also been targeted recently.
"It just seems to be a trend across the country at the moment and unfortunately it has hit us this time, we've certainly never had thefts on this scale before - not from the glasshouses.
"We ... think these are being stolen for sale.
"We're getting to the stage where we are putting some plants away now, we're just not going to put them on display."
Sole said it appeared house plants were becoming more popular with younger people.
They are fetching high prices online, with one - a Variegated Minima - breaking Trade Me's record for the cost of a plant at more than $8000.
Sole said the theft was gutting for staff and visitors alike and workers were on guard.
"It is uncomfortable because [staff] are looking twice at anybody now who comes into the Begonia House - and we have a lot of visitors through there.
"[The staff] get a big kick out of plants, they get a big kick out of people's reaction to them and being able to talk to people about plants and tell plants' stories - and if the plants have been stolen they can't.
"When new plants are stolen they are just not stolen from a glasshouse, they are stolen from the people of Wellington. And that is what really rankles."
Trade Me spokesperson Logan Mudge said the amount of house plants sold had rapidly increased alongside record-breaking prices.
"There's been a 235 percent increase of house plants sales on the site in the last year. Compared to five years ago, it's a two-and-a-half thousand percent jump in the number of sales."
Mudge said the site had a number of tools to weed out dodgy traders, and were working closely with the police as required.
NZ Garden magazine editor Jo McCarroll was concerned that this popularity was partially driven by plants looking appealing on instagram and other social media.
"I think it's a problem in that it is encouraging the sort of behaviour we've seen in Christchurch and now in Wellington where people are stealing plants that they think they will be able to sell for a profit, and that's devastating for the people who work in those places and all of the visitors who go to enjoy the range of plants that one can see. It's really heartbreaking."
The begonia house brings great joy to people like me without our own garden. This theft is an incredibly selfish act. https://t.co/b5VP2iD1y7— DeniseinWLG (@DeniseinWLG) October 13, 2020
First the vandalism at Zealandia, and now Begonia House is broken into. We are better than this Wellington. https://t.co/GMjSaqaJvh— Beckie (@FitKiwi) October 13, 2020