But behind the scenes a chill financial wind is blowing through one of Scotland’s most beloved institutions, as it struggles to cope after taking a £1 million hit in the collapse of the Icelandic banking system.

According to its latest accounts, the Royal Botanic Garden Edinburgh (RBGE) had £1.09m deposited with Kaupthing Singer & Friedlander when the financial firm went into administration last October, including RBGE’s entire £635,000 reserve fund and £450,000 set aside for a tax bill.

With all the cash frozen and half likely to be lost forever, RBGE’s board of trustees have now recommended introducing admission charges for the first time at the 189-year-old garden. It currently only charges for entry to the glasshouses, an adult ticket costing £3.50.

A ticket price of £4 has been floated, which would bring the pricing into line with RBGE’s three satellite gardens at Logan, Dawyck and Benmore. So far the Scottish government, which provided 85% of RBGE’s £18m income last year and has the final say on the entry fee, have baulked at the proposal.

However, the cash shortage has forced RBGE to cut back on its internationally-important scientific work, including research into climate change, conservation, and overseas expeditions. Only last week it was reported that RBGE-based research had discovered climate change was altering the world’s “botanical calendar”, with plants flowering earlier in the spring, potentially devastating the insects, birds and mammals that depend on them for food.

Vacancies for gardeners are also going unfilled. The new accounts say the charity’s trustees view the financial situation as “a serious risk to the future viability and sustainability” of RBGE’s work, and talks with Scottish ministers “are ongoing”.

The problems are expected to be discussed at RBGE’s annual meeting next month and MSPs on the Scottish parliament’s audit committee are also likely to take evidence on the matter.

Professor Stephen Blackmore, Regius Keeper (chief executive) of RBGE, described the loss of funds in the banking crisis as “disastrous”. He said: “That was the worst day of my working life, without a shadow of a doubt. Suddenly to find you’ve got a hole in your budget of over £1m is just nightmarish.”

He said research was being scaled down just as climate change made it all the more vital. “We are the people with the expertise to identify what all the different plants are, including the small and microscopic stuff which is hugely important in how the world works,” he said. “Without that kind of expertise you can’t even tell what changes are happening, let alone plan for how things might change in the future.”

The Icelandic bank’s administrators have so far repaid 20p in the pound, and believe RBGE may ultimately get back half its deposit, depending on how much is raised from selling the bank’s assets. But that still leaves a £500,000 hole in RBGE’s books. As a popular free attraction, Prof Blackmore said the trustees had recommended entry charges with “very mixed feelings”.

He said: “I like the free access model myself. Equally, we know a lot of our visitors would be quite happy to pay, particularly the overseas visitors who are often completely astonished you can get into a world-class garden without spending any money. But ultimately it’s a political decision, and I can well understand why ministers, up until now at any rate, have preferred that the garden would stay free admission.”

Picnicking with their two young daughters on the central lawn yesterday, Tracy and Richard Gee, both 37, reckoned people would probably pay £1 admission charge, but not much more.

“I think £4 a head would crucify the place,” said Richard. “They would need to be very careful.”

Sunbathing nearby, Alan Welsh, 69, a retired engineer, said: “It would be a great shame if they tried to charge. Lots of people just pass through, and they would stop coming.”

RBGE has 15,000 living species, a herbarium with nearly three million preserved specimens, and conservation projects from Peru to Arabia and South-east Asia. Last year it attracted 500,000 visitors.

A government spokesperson said: “We will consider any further issues when we know how much RBGE will be able to recover financially.”